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Recent investigations have improved our understanding of the molecular aberrations supporting Waldenström macroglobulinemia (WM) biology; however, whether the immune microenvironment contributes to WM pathogenesis remains unanswered. First, we showed how a transgenic murine model of human-like lymphoplasmacytic lymphoma/WM exhibits an increased number of regulatory T cells (Tregs) relative to control mice. These findings were translated into the WM clinical setting, in which the transcriptomic profiling of Tregs derived from patients with WM unveiled a peculiar WM-devoted messenger RNA signature, with significant enrichment for genes related to nuclear factor κB–mediated tumor necrosis factor α signaling, MAPK, and PI3K/AKT, which was paralleled by a different Treg functional phenotype. We demonstrated significantly higher Treg induction, expansion, and proliferation triggered by WM cells, compared with their normal cellular counterpart; with a more profound effect within the context of CXCR4C1013G-mutated WM cells. By investigating the B-cell–to–T-cell cross talk at single-cell level, we identified the CD40/CD40-ligand as a potentially relevant axis that supports WM cell–Tregs interaction. Our findings demonstrate the existence of a Treg-mediated immunosuppressive phenotype in WM, which can be therapeutically reversed by blocking the CD40L/CD40 axis to inhibit WM cell growth.

After spinal cord injury (SCI), patients face many physical and psychological issues including intestinal dysfunction and comorbidities, strongly affecting quality of life. The gut microbiota has recently been suggested to influence the course of the disease in these patients. However, to date only two studies have profiled the gut microbiota in SCI patients, months after a traumatic injury. Here we characterized the gut microbiota in a large Italian SCI population, within a short time from a not only traumatic injury. Feces were collected within the first week at the rehabilitation center (no later than 60 days after SCI), and profiled by 16S rRNA gene-based next-generation sequencing. Microbial profiles were compared to those publicly available of healthy age- and gender-matched Italians, and correlated to patient metadata, including type of SCI, spinal unit location, nutrition and concomitant antibiotic therapies. The gut microbiota of SCI patients shows distinct dysbiotic signatures, i.e. increase in potentially pathogenic, pro-inflammatory and mucus-degrading bacteria, and depletion of short-chain fatty acid producers. While robust to most host variables, such dysbiosis varies by lesion level and completeness, with the most neurologically impaired patients showing an even more unbalanced microbial profile. The SCI-related gut microbiome dysbiosis is very likely secondary to injury and closely related to the degree of completeness and severity of the lesion, regardless of etiology and time interval. This microbial layout could variously contribute to increased gut permeability and inflammation, potentially predisposing patients to the onset of severe comorbidities.

Background: Minimal residual disease (MRD) assessment retains high prognostic value in Acute Myeloid Leukemia patients (AML) undergoing intensive induction therapy. Widely available MRD techniques include multicolour flow cytometry (MFC), RT-PCR for recurrent genetic lesion and, for patients lacking specific markers, RT-PCR for the pan- leukemic marker WT1. However, most of the data on the prognostic value of MRD come from trials including younger patients treated with conventional 3+7 regimen. AML arising from a previous myelodisplastic syndrome (s-AML) and therapy-related AML (t-AML) are usually under-represented in trial involving younger patients and are unlikely to respond to conventional induction. Few data are therefore available on the kinetics and the prognostic value of MRD in elderly s- AML and t-AML patients, particularly in the context of alternative induction regimens. Aims: We evaluated MRD in a cohort of elderly s-AML or t-AML patients receiving induction therapy either with a fludarabine-containing regimen or CPX-351, in order to compare the probability of achieving MRD negativity, to disclose the prognostic value of MRD in this setting and to define the best time-points for MRD assessments. Methods: A total of 136 elderly (>60 year, median age 67, range 60-75) patients were analyzed in this study. Patients were treated between January 2005 and January 2020 in our Center, either with CPX-351 (n=35) or fludarabine- high dose cytarabine-idarubicin (FLAI), with (n=72) or without (n =29) gemtuzumab-ozogamicin (GO). MRD was retrospectively analyzed in all patients achieving hematological complete remission (CR) with both MFC and WT1 expression levels.All patients were affected by s-AML or t-AML, defined according to the WHO 2016 criteria. Results: After induction, CR was achieved in 83 patients (61%). CR rate was 28/35 in patients treated with CPX-351 (80%), significantly higher when compared to patients receiving FLAI (55/101, 54.5%, p Moreover, MRD showed significant prognostic value in terms of Overall Survival in all treatment group (2-year OS of 74 and 36% in patients with or without residual MFC MRD after induction, respectively, p Conclusion: In conclusion MRD assessment retains a strong prognostic value and may help to identify patients with suboptimal response to treatment. The higher rate of MRD negativity observed with CPX-351 may be related with a more efficient anti-leukemic activity of the drug in this particular setting. The evaluation of MRD with both MFC and WT1-based assessment lead to superimposable conclusions and allowed us to obtain MRD data from virtually all AML patients treated in the selected time period. Disclosures No relevant conflicts of interest to declare.

Genomic instability plays a pathological role in various malignancies, including acute myeloid leukemia (AML), and thus represents a potential therapeutic target. Recent studies demonstrate that SIRT6, a NAD + -dependent nuclear deacetylase, functions as genome-guardian by preserving DNA integrity in different tumor cells. Here, we demonstrate that also CD34 + blasts from AML patients show ongoing DNA damage and SIRT6 overexpression. Indeed, we identified a poor-prognostic subset of patients, with widespread instability, which relies on SIRT6 to compensate for DNA-replication stress. As a result, SIRT6 depletion compromises the ability of leukemia cells to repair DNA double-strand breaks that, in turn, increases their sensitivity to daunorubicin and Ara-C, both in vitro and in vivo In contrast, low SIRT6 levels observed in normal CD34 + hematopoietic progenitors explain their weaker sensitivity to genotoxic stress. Intriguingly, we have identified DNA-PKcs and CtIP deacetylation as crucial for SIRT6-mediated DNA repair. Together, our data suggest that inactivation of SIRT6 in leukemia cells leads to disruption of DNA-repair mechanisms, genomic instability and aggressive AML. This synthetic lethal approach, enhancing DNA damage while concomitantly blocking repair responses, provides the rationale for the clinical evaluation of SIRT6 modulators in the treatment of leukemia.

Multiple myeloma (MM) is characterized by a highly unstable genome, with aneuploidy observed in nearly all patients. The mechanism causing this karyotypic instability is largely unknown, but recent observations have correlated these abnormalities with dysfunctional DNA damage response. Here, we show that the NAD(+)-dependent deacetylase SIRT6 is highly expressed in MM cells, as an adaptive response to genomic stability, and that high SIRT6 levels are associated with adverse prognosis. Mechanistically, SIRT6 interacts with the transcription factor ELK1 and with the ERK signaling-related gene. By binding to their promoters and deacetylating H3K9 at these sites, SIRT6 downregulates the expression of mitogen-activated protein kinase (MAPK) pathway genes, MAPK signaling, and proliferation. In addition, inactivation of ERK2/p90RSK signaling triggered by high SIRT6 levels increases DNA repair via Chk1 and confers resistance to DNA damage. Using genetic and biochemical studies in vitro and in human MM xenograft models, we show that SIRT6 depletion both enhances proliferation and confers sensitization to DNA-damaging agents. Our findings therefore provide insights into the functional interplay between SIRT6 and DNA repair mechanisms, with implications for both tumorigenesis and the treatment of MM.

Here we report a case of a 32-year-old man, who was diagnosed as having chronic myeloid leukaemia in 1998. After cytoreduction with hydroxyurea, the patient was submitted to high dose chemotherapy with haemopoietic stem cells rescue and reinfusion, and then he started therapy with IFNα without achievement of a cytogenetic response. On November 2000 he took imatinib 400 mg/day and he reached a complete cytogenetic response (CCyR) at 14 months, but not the major molecular response: therefore he was considered a sub-optimal responder according to European LeukemiaNet criteria of 2006. For this reason he increased imatinib dose to 800 mg/day, but after one year he lost CCyR. Considering the patient as a failure, at this time, he switched to second-generation tyrosine kinase inhibitor, nilotinib at the dose of 800 mg/day. After 3 months he reached complete CCyR and after 6 months the major molecular response, maintained until last molecular evaluation.

Background Blastic plasmacytoid dendritic cell neoplasm (BPDCN) are a very rare group of diseases included by WHO 2016 classification among the myeloid neoplasms and usually display an aggressive course with dismal outcome. BPDCN are characterized by a recurrent phenotype (CD45low/CD34-/CD56+/CD4+/CD123+), in the absence of other lineage differentiation markers. Our group recently reported that a subset of patients diagnosed with AML with NPM1-mutation carrying co-expression of CD123, CD56 and CD4, a "BPDCN-like" phenotype, showed poor prognosis. The aim of the present study was to evaluate the incidence and the prognostic impact of BPDCN-like phenotype in a wider cohort of cytogenetically normal AML patients, irrespectively of NPM1-mutational status. Methods We retrospectively evaluated a cohort of 83 younger (age In all patient, 4 (until 2012) or 8 color immunophenotypic analysis was performed at diagnosis by analysing erythrocyte-lysed whole BM blasts to identify relevant antigen aberration patterns and the pathological leukemia phenotype for future minimal residual disease assessment. We defined a BPDCN-like signature the positivity of at least two among CD56/CD4/CD123 antigens and we evaluated the prognostic impact and the correlation with biological, molecular and cytogenetic features. Results Fifteen patients (18%) showed a BPDCN-like signature. Neither the presence of NPM1-mutation nor FLT3-ITD or biallelic CEBPA mutation showed a significant correlation with BPDCN-like signature. BPDCN-like patients had significantly higher WBC count at diagnosis (p Among analyzed variables, only the presence of NPM1-mutation correlated with complete response (CR) probability. With a median follow-up of 63 months, 3-year Overall Survival (OS) was 52% in the whole cohort (median 38 months). Patient with NPM1 mutation or biallelic CEBPA mutation had a better outcome (p However, as we previously reported, in the subgroup of 30 patients with NPM-1 mut AML, the presence of BPDCN-like features conferred a poor prognosis (3-year OS 25% vs 77% for BPDCN positive and negative NPM-1 mut patients, respectively, p On the contrary in the 38 NPM-1 wt patients a trend towards better outcome was observed in BPDCN-like patient, unless not statistically significant (3-year OS 71% vs 35% for BPDCN-like positive and negative NPM-wt patients, respectively, p=0.156). No difference in MRD clearance probability was observed in this subgroup. Conclusions Our extended analysis confirms that a peculiar BPDCN-like immunophenotype among NPM-1 mut AML patients is associated with significantly worse outcome in this otherwise favorable subset of AML. Patient with BPDCN-like features showed high level of minimal residual disease after induction, suggesting an intrinsic chemo-resistance. Interestingly, this observation was strictly restricted to NPM-1 mutated AML, suggesting that peculiar alterations in this distinct entity contribute to the prognostic impact of BPDCN-like features in this setting. The biological explanation of this finding is not clear and further gene-expression profiling studies are ongoing in order to explain our findings. Figure. Figure. Disclosures Gobbi: Pfister: Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; Ariad: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy.

Background: The addition of the anti-CD33 targeting antibody Mylotarg (MY) to conventional "3+7" induction has been shown to improve the outcome of patients affected by acute myeloid leukemia (AML) without adverse cytogenetic alterations. Early reports suggested that MY was particularly effective among low risk patients, such as core binding factor AML, particularly if included in a high dose cytarabine-based induction therapy. The role of MY for intermediate risk patients appears to be less clear. Cytogenetically defined intermediate risk patients may be further stratified considering two frequent molecular aberrations: FLT3 "internal tandem duplication" (FLT3-ITD) mutation, associated with poor prognosis and NPM1 mutation (NPM1-mut), associated with a good prognosis. The concomitant presence of NPM1-mutpartially overcomes the negative prognostic impact of FLT3-ITD, which is also modulated by FLT3-ITD/wild type allelic ratio. NPM1 and FLT3 mutational status assessment is strongly recommended for risk stratification at diagnosis by the last ELN 2017 guidelines. Aims: To investigate the efficacy of MY added to an intensive fludarabine, high dose cytarabine and Idarubicin-based induction regimen (FLAI) as frontline treatment for younger ( Methods:One-hundred and forty eight consecutive AML patients, treated in 3 Italian Hematology centersbetween 2008 and 2018and harboring at least one molecular alteration among NPM1-mut and FLT3-ITD, were included in the analysis. Thirty three patients carried isolated FLT3-ITD, 50patients showed concomitant FLT3-ITD and NPM1-mut and 65 isolated mutated NPM-1.Median age was 50 years(range: 18-65). All patients received FLAI induction (fludarabine 30 mg/sqm and ARA-C 2g/sqm on days1 to 5 plus idarubicin 10 mg/sqm on days 1-3-5), with or without low dose MY(3 mg/sqm, added in 42 patients), followed by a second induction without fludarabine and with idarubicin at the increased dose of 12 mg/sqm. Before 2017, patients with isolated FLT3-ITD mutation were scheduled for allogeneic stem cell transplantation (HSCT), if an HLA-matched sibling donor was available, whereas after 2017 only patients with high allelic burden isolated FLT3-ITD mutation received HSCT in first CR. The other patients received conventional high dose cytarabine consolidation for a total of 3 cycles. Results: Overall, 60-days mortality was 3%, and was not significantly influenced by receiving or not MY during induction. After one induction cycle, 126 patients achieved CR (85%) with no difference between patients receiving or not MY. After a median follow up of 70months, 3-year overall survival (OS) was 59.5% (median not reached). OS duration was significantly longer in NPM1 mutated patients (p Conclusions: Despite the potential bias due to the retrospective nature of the analysis, our data seem to indicate that Mylotarg, added to an intensive fludarabine/high dose cytarabine-based induction, provides a significant improvement in anti-leukemic efficacy in patients carrying FLT3-ITD mutation, especially if concomitant NPM1 mutation is not present. Disclosures Candoni: Gilead: Honoraria, Speakers Bureau; Celgene: Honoraria; Pfizer: Honoraria; Janssen: Honoraria; Merck SD: Honoraria, Speakers Bureau. Bocchia:Novartis: Honoraria; Incyte: Honoraria; BMS: Honoraria.

Over the past decades the prognosis of patients with Chronic Myeloid Leukemia (CML) has radically changed due to groundbreaking scientific and translational studies that have revealed the biologic basis of such a hematologic malignancy. These studies have led to the rapid development of many BCR-ABL specific tyrosine kinase inhibitors (TKIs), such as Imatinib, Nilotinib and Dasatinib, which have improved 10-years survival to more than 80%. Although these therapies represent a landmark step in the race for the cure of CML, they did not change the progression in advanced phase of disease. Therefore unravel the molecular mechanisms and the biological basis of CML, especially during the advanced stage, is of seminal importance as this would result in the design of more effective and less toxic therapies. In such a scenario, several novel drugs designed to specifically target biological features of CML cells are currently in clinical trials with promising results that would provide not only improve the therapeutic armamentarium but also to overcome drug resistance of this tumor. Here we review recent advances in biology of CML and their therapeutic implications.

Purpose: Nicotinamide phosphoribosyltransferase (Nampt) regulates intracellular NAD+ pool and is highly expressed in a number of malignancies. FK866, a selective inhibitor of Nampt, depletes intracellular NAD+ levels, thereby blocking cellular metabolism and triggering sensitization to other drugs and cell death. Here we characterized the antitumor effects of Nampt inhibition in Waldenström macroglobulinemia. Experimental Design: We investigated Nampt role in MW cells using both mRNA and protein expression analyses. We have also used loss-of-function approaches to investigate the growth and survival effects of Nampt on MW cells and further tested the anti-MW activity of dual Nampt and BTK inhibition in vitro and in vivo. Results: We found that Waldenström macroglobulinemia cells exhibit high levels of Nampt compared with normal B cells. Loss of function studies suggested a potential oncogenic role of Nampt in Waldenström macroglobulinemia cells, and BTK-inhibitor ibrutinib and FK866 resulted in a significant and synergistic anti-Waldenström macroglobulinemia cell death, regardless of MYD88 and CXCR4 mutational status. Cell death was associated with: (i) activation of caspase-3, PARP and downregulation of Mcl-1, (ii) enhanced intracellular ATP and NAD+ depletion, (iii) inhibition of NF-κB signaling, and (iv) inhibition of multiple prosurvival signaling pathways. In a murine xenograft Waldenström macroglobulinemia model, low-dose combination FK866 and ibrutinib is well tolerated, significantly inhibits tumor growth, and prolongs host survival. Conclusions: Our results show intracellular NAD+ level as crucial for proliferation and survival of Waldenström macroglobulinemia cells, and provides the mechanistic preclinical rationale for targeting Nampt, either alone or with Ibrutinib, to overcome drug resistance and improve patient outcome in Waldenström macroglobulinemia. Clin Cancer Res; 22(24); 6099–109. ©2016 AACR.

We reviewed the frequency and prognostic significance of FLT3 (fms-like tyrosine kinase receptor-3) and NPM (nucleophosmin) gene mutations and WT1 (Wilms' tumor) and BAALC (brain and acute leukemia, cytoplasmic) gene expression in 100 consecutive patients with intermediate and poor cytogenetic risk de novo acute myeloid leukemia (AML) receiving conventional anthracycline-AraC based therapy. We observed a strict relationship between unfavorable karyotype and BAALC1000 (p = 0.0001). Multivariate analysis of 81 patients with intermediate karyotype revealed that younger age (p = 0.00009), NPM gene mutation (p = 0.002), and WT175th percentile (2365) (p = 0.003) were independent, positive factors for complete remission (CR). WT1 expression above 2365 was correlated also to longer event-free survival (EFS) and overall survival (OS) in the same subset of patients (p = 0.003 and p = 0.02, respectively); the same finding occurred in younger patients with AML with intermediate karyotype (p = 0.008 and p = 0.01, respectively). In patients with intermediate karyotype, FLT3 internal tandem duplication (ITD) negatively affected EFS (EFS at 30 months: 30% vs. 6% in FLT3-ITD negative and FLT3 positive patients, respectively; p = 0.01) and OS (OS at 30 months: 38% vs. 20%, p = 0.03). The positive prognostic value of high WT1 expression does not have a clear explanation; it may be implicated either with WT1 anti-oncogenic function, or with the stimulating effect of WT1 oncogene on the leukemic cellular cycle, possibly associated with an enhanced response to chemotherapy.

Background: Human tumours rely on Glutamine (Gln) metabolism to sustain wide range of metabolic processes and macromolecules synthesis. Such dependence defined as "Gln-addiction" has been recently observed also for Multiple Myeloma (MM) cells, where Gln synthetase deficiency make them more sensitive to Gln depletion. L-Asparaginase (L-ASP), the enzyme that catalyzes asparagine (Asn) and Gln hydrolysis, represents a key drug for B-cells derived malignancies treatment such as acute lymphoblastic leukemia. Aims: The aim of the present study was to screen MM cells sensitivity to pharmacological Gln depletion achieved by Erwinia chrysantemi-derived L-ASP treatment as single agent as well as in combination with proteasome inhibitors (PIs). Based on its high glutaminase activity, E. chrysantemi L-ASP was selected for this screening. Materials and methods: The IC50 value of L-ASP was determined by MTS assay in a panel of human MM cell lines (HMCLs) harboring different genetic background as well as on primary CD138+ cells derived from newly diagnosed (NDMM) and and relapsed/refractory (RRMM) MM patients. Cell death analysis was measured with Annexin V/Propidium Iodide (AV/PI) staining followed by flow-cytometric analysis. L-ASP treatment effect on cell viability and mitochondrial membrane potential was evaluated by FACS analysis following PI and TMRE staining, respectively. Intracellular ATP levels was also measured by HPLC-based method. Drugs combination screening with L-ASP plus PIs including bortezomib (BZ) or carfilzomib (KAR) was investigated by using isobologram analysis (CalcuSyn software program). Finally, western blot analysis was employed to fully elucidate biological mechanisms of our findings. Results: L-ASP treatment showed potent anti-MM activity in all HMCLs tested with an IC50 values ranging from 0,03 U/mL to 0.2 U/mL. Importantly, such drug preserved its effect also on primary tumor cells obtained from NDMM and RRMM patients (IC50 =0.06 U/mL). Cell cycle analysis revealed an early (24 h) but irreversible "metabolic shutdown" in MM cells treated with L-ASP which led to late mitochondrial stress (48-72h). To further confirm Gln specific role in the observed finding, MM cells viability was measured in presence of different culture media conditions. Asn depletion alone did not modify significantly MM cells viability, instead it strongly contributed to L-ASP induced toxicity of Gln-starved cells. Co-treatment experiments showed massive increase of its anti-MM activity when L-ASP was used in presence of low doses of BZ and KAR, with a combination index below than 1 in all tested drugs-concentrations. Accordingly, caspase-3 and PARP cleavage showed apoptotic cell death features of this co-treatment. Importantly, IL6 or IGF-1 addition did not reduce anti-MM activity of this combination suggesting that MM microenvironment does not reduce efficacy of this strategy. Finally, mechanistic studies revealed higher ATP shortage in co-treated cells together with c-MYC down-regulation, genomic instability and misfolded proteins accumulation, suggesting a massive proteasome activity impairment triggered by these drugs-combination. Ongoing experiment will help to further elucidate this hypothesis. Conclusions: Our preliminary data show that E. chrysantemi L-ASP exerts a potent anti-MM activity mainly due to its glutaminase activity, which results in a massive metabolic program deregulation. The combination with low-doses of PIs further increases anti-MM activity of this small molecule likely due to huge proteasome activity injury. Disclosures Gobbi: Amgen: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees; Ariad: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Janssen: Consultancy; Pfister: Membership on an entity's Board of Directors or advisory committees.

Here we show that overexpression or activation of B-cell maturation antigen (BCMA) by its ligand, a proliferation-inducing ligand (APRIL), promotes human multiple myeloma (MM) progression in vivo. BCMA downregulation strongly decreases viability and MM colony formation; conversely, BCMA overexpression augments MM cell growth and survival via induction of protein kinase B (AKT), MAPK, and nuclear factor (NF)-κB signaling cascades. Importantly, BCMA promotes in vivo growth of xenografted MM cells harboring p53 mutation in mice. BCMA-overexpressing tumors exhibit significantly increased CD31/microvessel density and vascular endothelial growth factor compared with paired control tumors. These tumors also express increased transcripts crucial for osteoclast activation, adhesion, and angiogenesis/metastasis, as well as genes mediating immune inhibition including programmed death ligand 1, transforming growth factor β, and interleukin 10. These target genes are consistently induced by paracrine APRIL binding to BCMA on MM cells, which is blocked by an antagonistic anti-APRIL monoclonal antibody hAPRIL01A (01A). 01A is cytotoxic against MM cells even in the presence of protective bone marrow (BM) myeloid cells including osteoclasts, macrophages, and plasmacytoid dendritic cells. 01A further decreases APRIL-induced adhesion and migration of MM cells via blockade of canonical and noncanonical NF-κB pathways. Moreover, 01A prevents in vivo MM cell growth within implanted human bone chips in SCID mice. Finally, the effect of 01A on MM cell viability is enhanced by lenalidomide and bortezomib. Taken together, these data delineate new molecular mechanisms of in vivo MM growth and immunosuppression critically dependent on BCMA and APRIL in the BM microenvironment, further supporting targeting this prominent pathway in MM.

To the editor: Nahimana and coworkers have recently reported that the nicotinamide phosphoribosyltransferase (NAMPT) inhibitor APO866 elicited massive cell death in primary leukemia cells and in numerous leukemia/lymphoma cell lines.[1][1] In particular, in 32 primary leukemias (including 12 B-cell

B-cell maturation antigen (BCMA), highly expressed on malignant plasma cells in human multiple myeloma (MM), has not been effectively targeted with therapeutic monoclonal antibodies. We here show that BCMA is universally expressed on the MM cell surface and determine specific anti-MM activity of J6M0-mcMMAF (GSK2857916), a novel humanized and afucosylated antagonistic anti-BCMA antibody-drug conjugate via a noncleavable linker. J6M0-mcMMAF specifically blocks cell growth via G2/M arrest and induces caspase 3-dependent apoptosis in MM cells, alone and in coculture with bone marrow stromal cells or various effector cells. It strongly inhibits colony formation by MM cells while sparing surrounding BCMA-negative normal cells. J6M0-mcMMAF significantly induces effector cell-mediated lysis against allogeneic or autologous patient MM cells, with increased potency and efficacy compared with the wild-type J6M0 without Fc enhancement. The antibody-dependent cell-mediated cytotoxicity and apoptotic activity of J6M0-mcMMAF is further enhanced by lenalidomide. Importantly, J6M0-mcMMAF rapidly eliminates myeloma cells in subcutaneous and disseminated mouse models, and mice remain tumor-free up to 3.5 months. Furthermore, J6M0-mcMMAF recruits macrophages and mediates antibody-dependent cellular phagocytosis of MM cells. Together, these results demonstrate that GSK2857916 has potent and selective anti-MM activities via multiple cytotoxic mechanisms, providing a promising next-generation immunotherapeutic in this cancer.

We recently demonstrated that Nicotinamide phosphoribosyltransferase (Nampt) inhibition depletes intracellular NAD⁺ content leading, to autophagic multiple myeloma (MM) cell death. Bortezomib has remarkably improved MM patient outcome, but dose-limiting toxicities and development of resistance limit its long-term utility. Here we observed higher Nampt messenger RNA levels in bortezomib-resistant patient MM cells, which correlated with decreased overall survival. We demonstrated that combining the NAD⁺ depleting agent FK866 with bortezomib induces synergistic anti-MM cell death and overcomes bortezomib resistance. This effect is associated with (1) activation of caspase-8, caspase-9, caspase-3, poly (ADP-ribose) polymerase, and downregulation of Mcl-1; (2) enhanced intracellular NAD⁺ depletion; (3) inhibition of chymotrypsin-like, caspase-like, and trypsin-like proteasome activities; (4) inhibition of nuclear factor κB signaling; and (5) inhibition of angiogenesis. Furthermore, Nampt knockdown significantly enhances the anti-MM effect of bortezomib, which can be rescued by ectopically overexpressing Nampt. In a murine xenograft MM model, low-dose combination FK866 and Bortezomib is well tolerated, significantly inhibits tumor growth, and prolongs host survival. Taken together, these findings indicate that intracellular NAD⁺ level represents a major determinant in the ability of bortezomib to induce apoptosis in MM cells and provide proof of concept for the combination with FK866 as a new strategy to enhance sensitivity or overcome resistance to bortezomib.

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder characterized by the expansion of a leukemic stem cell (LSC) clone, carrying a Philadelphia translocation, able to overcome the non-malignant hematopoietic stem cells. The tyrosine kinase inhibitors (TKIs) imatinib, nilotinib and dasatinib are gold-standard for CML treatment. Each shows an impressive rate of complete cytogenetic response in chronic phase (CP)-CML. However, relapse and treatment failure are major problems with long-term use of TKIs. A polymerase chain reaction (PCR) assay to detect the mRNA expression of BCR-ABL1 represents the main molecular approach to monitoring response to treatment. However, using this analysis it is currently not possible to prospectively identify patients whose disease will relapse due to LSC reappearance. The aim of our study was to investigate whether the mRNA expression analysis of two Hedgehog (Hh) stemness signaling molecules, Smoothened (SMO) and Patched-1 (PTCH1), could predict upcoming molecular relapse. At the time of diagnosis, patients with high Sokal risk (n = 12) showed higher and lower levels of SMO and PTCH1, respectively (p = 0.0132), compared with patients with different Sokal scores (p = 0.0316 for intermediate risk and p = 0.0340 for low risk). These data suggest that Hh signaling was functionally more active in this risk group at the time of diagnosis. Furthermore, the kinetics of Hh signaling activity during the individual medical history correlated with BCR-ABL1 mRNA level and with upcoming molecular relapse. Also, mutation analysis of BCR-ABL1 revealed that activation of Hh signaling precedes molecular relapse by several months, mostly in patients carrying the gatekeeper mutation T315I. Importantly, in vitro data showed a synergistic effect of chemical inhibitors of Hh signaling and TKIs in both wild-type and resistant (T315I) CML cell lines. Collectively our data show that monitoring Hh pathway activity contemporaneously with BCR-ABL1 mRNA level may improve the chance of early detection of patients who will experience a relapse (mainly in the high Sokal risk group), paving the way for an innovative management of this hematologic malignancy.

Currently available therapeutics against Acute Myeloid Leukemia (AML) have improved patient outcome. However, resistance develops even to novel therapies and patient overall survival remains low, especially for patients who are not eligible for allogeneic bone marrow transplantation. Therefore, there is an urgent need to overcome the biologic mechanisms underlying drug resistance in AML, to enhance the efficacy of existing treatments and to facilitate the design of novel approaches. Recently, our group has demonstrated that SIRT6, a NAD+-dependent histone deacetylase involved in genome maintenance, is frequently up-regulated in Multiple Myeloma and its targeting induces cancer cell killing (Cea M. et al, Blood 2016). Furthermore, gene expression analyses performed by our groups show that SIRT6 is also up-regulated in AML and confers poor prognosis in a series of 200 primary AML cases from our Hematology Clinic. Thus, these data suggested a role for SIRT6 in AML biology. High SIRT6 expression was typically observed in AML cell lines characterized by constitutive DNA damage and intense replicative stress. Likewise, primary AML cases exhibiting an intermediate-to-high chromosome instability (CIN) gene expression signature were also those with the highest SIRT6 expression, and worst prognosis. Subsequent studies demonstrated that SIRT6 silencing or its chemical inhibition, as observed in Multiple Myeloma exacerbates DNA damage in response to genotoxic agents, sensitizing AML cells to cytarabine (ARA-C) and idarubicin in vitro. Overall, enhancing genotoxic stress while concomitantly blocking DNA double-strand breaks (DSBs) repair response, may represent an innovative strategy to increase chemosensitivity of AML cells. Mechanistic studies revealed that SIRT6 acts as a genome guardian in AML cells by binding DNA damage sites and activating DNA-PKcs and CtIP by deacetylation, which in turn promotes DNA repair. Overall our data suggest that genomic instability is present in all hematologic malignancies including AML. Strategies aimed to shift the balance towards high DNA damage and reduced DNA repair by SIRT6 inhibition can decrease AML growth and may benefit patients with otherwise unfavorable outcomes. Disclosures Gobbi: Gilead: Honoraria; Takeda: Consultancy; Janssen: Consultancy, Honoraria; Roche: Honoraria; Celgene: Consultancy; Mundipharma: Consultancy, Research Funding; Novartis: Consultancy, Research Funding.

Background: The upregulated NAD+ biosynthesis, which is needed to face increased proliferation and metabolic processes, represents an important feature distinguishing cancer cells from their normal counterparts. As a result, the NAD+ biosynthetic apparatus emerges as highly promising therapeutic target for tumors, as suggested by the use of nicotinamide phosphoribosyltransferase (NAMPT) inhibitors in a number of malignancies, including Multiple Myeloma (MM) and leukemia (Cea et al. Blood 2012; Cagnetta et al. Blood 2013; Cagnetta et al. CCR 2015). The ecto-enzyme CD38 is emerging as a novel therapeutic target for patients with hematological malignancies, including MM, with several monoclonal antibodies already tested in clinical trials with promising results. Importantly, CD38 by regulating intracellular NAD+ stores acts as member of the intricate network supporting metabolic reprogramming associated with cancer. Based on these assumptions, here we explored CD38 activity as innovative strategy to enhance the anti-tumor activity of NAMPT inhibition in Multiple Myeloma cells. Methods: A panel of different MM cell lines and primary cells, both sensitive and resistant to conventional and novel anti-MM therapies, was used in the study. The effects of Nampt inhibition was evaluated in presence of CD38-gene editing (loss/gain of approaches) by using CTG assay and Annexin-V/propidium iodide staining. Next, the anti-MM effects of chemicals affecting CD38 activity were also evaluated in combination with low doses of Nampt inhibitors. Mechanistic studies were performed with Western-blotting, lentivirus-mediated shRNAs and enzymatic assays. Results and Conclusions: By using different approaches, we found that CD38 deregulation makes MM cells more vulnerable to NAD+ depleting agents. Ongoing mechanistic studies suggest the central role played by energetic metabolism in the observed synergism. Overall our data provide the mechanistic preclinical rationale to enhance anti-MM activity of Nampt targeting agents, in order to both overcome drug resistance and improve patients outcome. Disclosures Gobbi: Mundipharma: Consultancy, Research Funding; Takeda: Consultancy; Roche: Honoraria; Celgene: Consultancy; Gilead: Honoraria; Novartis: Consultancy, Research Funding; Janssen: Consultancy, Honoraria.

Elevated B cell maturation antigen (BCMA) and its ligand a proliferation-inducing ligand (APRIL) may directly advance human multiple myeloma (MM) malignancy in vivo. Here, we first show that BCMA downregulation potently diminishes viability and colony formation of MM cells while BCMA overexpression augments MM cell growth and survival via induction of AKT, MAPK, and NFκB signaling cascades and molecules essential for proliferation and anti-apoptosis. Importantly, BCMA itself forces accelerated tumor growth of xenografted MM cells harboring p53 mutation in mice. BCMA-overexpressing tumors exhibit significantly enhanced CD31/microvessel density and VEGF than paired control tumors. Concurrently, these tumors express increased factors crucial for osteoclast activation, adhesion, and angiogenesis/metastasis, as well as immune inhibition including PD-L1, TGFβ and IL-10 which further triggers 38 IL-10 signaling molecules. In parallel, these identified target genes are induced by paracrine APRIL binding to BCMA in MM cells and they are potently blocked by an antagonistic anti-APRIL monoclonal antibody hAPRIL01A (01A). 01A is cytotoxic against MM cells protected by abnormal bone marrow (BM) myeloid cells, i.e., osteoclasts, macrophages, and plasmacytoid dendritic cells. It further decreases APRIL-induced adhesion and migration of MM cells via blockade of canonical and non-canonical NFκB pathways. It prevents in vivo MM cell growth within implanted human bone chips in SCID mice. 01A-inhibited MM cell viability induced by osteoclasts is further enhanced by lenalidomide and bortezomib. Taken together, these results further characterize new molecular mechanisms of APRIL/BCMA-induced in vivo MM progression and immunosuppressive BM microenvironment, strongly supporting targeting this prominent pathway in MM. Citation Format: Yu-Tzu Tai, Chirag Acharya, Gang An, Michele Moschetta, Mike Y. Zhong, Xiaoyan Feng, Michele Cea, Antonia Cagnetta, Kenneth Wen, Hans van Eenennaam, Andrea van Elsas, Nikhil Munshi, Kenneth Anderson. APRIL/BCMA activation promotes human multiple myeloma progression and further induces immunosuppressive bone marrow microenvironment. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3283.

Chronic myeloid leukemia (CML) is a hematological disease accounting for about 15-20% of all adult leukemias. The clinical and biologic advances achieved in such a malignancy, represent one of the best successes obtained by translational medicine. Indeed, identification of the fusion oncogene BCR-ABL has allowed using of small molecule inhibitors of its tyrosine kinase activity which, in turn, have literally revolutionized the treatment of CML. Importantly the successfully clinical management was also realized on appropriate diagnosis, disease monitoring as well as early identification of such mutations causing drug resistance. Notably the recent availability of refined laboratory equipments represented by the Next Generation Sequencing (NGS) and genomic analyses has further contributed to gain ground towards the cure of this tumor. These issues are discussed here together with an overview on how patients treated with tyrosine kinase inhibitors should be monitored.

Malignant cells have a higher nicotinamide adenine dinucleotide (NAD+) turnover rate than normal cells, making this biosynthetic pathway an attractive target for cancer treatment. Here we investigated the biologic role of a rate-limiting enzyme involved in NAD+ synthesis, Nampt, in multiple myeloma (MM). Nampt-specific chemical inhibitor FK866 triggered cytotoxicity in MM cell lines and patient MM cells, but not normal donor as well as MM patients PBMCs. Importantly, FK866 in a dose-dependent fashion triggered cytotoxicity in MM cells resistant to conventional and novel anti-MM therapies and overcomes the protective effects of cytokines (IL-6, IGF-1) and bone marrow stromal cells. Nampt knockdown by RNAi confirmed its pivotal role in maintenance of both MM cell viability and intracellular NAD+ stores. Interestingly, cytotoxicity of FK866 triggered autophagy, but not apoptosis. A transcriptional-dependent (TFEB) and independent (PI3K/mTORC1) activation of autophagy mediated FK866 MM cytotoxicity. Finally, FK866 demonstrated significant anti-MM activity in a xenograft-murine MM model, associated with down-regulation of ERK1/2 phosphorylation and proteolytic cleavage of LC3 in tumor cells. Our data therefore define a key role of Nampt in MM biology, providing the basis for a novel targeted therapeutic approach.

Bruton tyrosine kinase (Btk) has a well-defined role in B-cell development, whereas its expression in osteoclasts (OCs) further suggests a role in osteoclastogenesis. Here we investigated effects of PCI-32765, an oral and selective Btk inhibitor, on osteoclastogenesis as well as on multiple myeloma (MM) growth within the BM microenvironment. PCI-32765 blocked RANKL/M-CSF–induced phosphorylation of Btk and downstream PLC-γ2 in OCs, resulting in diminished TRAP5b (ED50 = 17nM) and bone resorption activity. PCI-32765 also inhibited secretion of multiple cytokines and chemokines from OC and BM stromal cell cultures from both normal donors (ED50 = 0.5nM) and MM patients. It decreased SDF-1–induced migration of MM cells, and down-regulated MIP1-α/CCL3 in MM cells. It also blocked MM cell growth and survival triggered by IL-6 or coculture with BM stromal cells or OCs in vitro. Importantly, PCI-32765 treatment significantly inhibits in vivo MM cell growth (P < .03) and MM cell–induced osteolysis of implanted human bone chips in SCID mice. Moreover, PCI-32765 prevents in vitro colony formation by stem-like cells from MM patients. Together, these results delineate functional sequelae of Btk activation mediating osteolysis and growth of MM cells, supporting evaluation of PCI-32765 as a novel therapeutic in MM.

Abstract 2920 Background: Nicotinamide adenine dinucleotide (NAD+) is a coenzyme crucially involved in several cellular functions, including energy metabolism, reactive oxygen species scavenging, DNA repair, and gene expression. Intracellular NAD+ stores are continuously replenished through pathways whose activity depends on the tissue and availability of substrates. Nicotinamide phosphoribosyltransferase (Nampt) is the rate-limiting enzyme in the NAD+ salvage pathway from nicotinamide. During neoplastic transformation, Nampt is upregulated to compensate for increased metabolic demands. It promotes myeloid and lymphoid differentiation and increases specific cytokine production (TNF- α, IL-6 and VEGF). Importantly, cancer and leukaemia cells appear to be more sensitive to Nampt inhibitor drugs than normal cells. The reasons for this selectivity are not fully understood, but may include aberrant metabolic demands and increased reliance on NAD+-dependent enzymes. Promising results obtained with Nampt inhibitors (such as FK866) in preclinical cancer models suggest that Nampt activity represents an innovative therapeutic target for novel anticancer agents. Methods: A panel of eighteen different MM cell lines, both sensitive and resistant to conventional and novel anti-myeloma drugs, as well as patient MM cells were used in the study. The mechanism of action of FK866 was investigated by Annexin-V/propidium iodide staining, thymidine incorporation, Western-blotting, and with lentivirus-mediated shRNAs. For the autophagy assay, EGFP-LC3+ cells were treated with FK866 and the number of GFP-LC3 punctae was analyzed and quantified by fluorescence microscopy and flow cytometry, respectivley. Intracellular NAD+ content was measured using a biochemical assay. Angiogenesis was measured in vitro using Matrigel capillary-like tube structure formation assay. Results: To study the role of Nampt in MM cells, we performed a protein analysis of this enzyme in eighteen MM cell lines. Nampt is constitutively activated in all cell lines tested. Moreover, patient MM cells highly express this enzyme whereas normal cells lack this protein. Indeed, the Nampt inhibitor FK866 decreased MM cell line viability in a dose and time dependent manner, with an IC50 ranging from 3–30nM. Similar results were observed in patient MM cells. Importantly, FK866 did not inhibit viability of normal peripheral blood mononuclear cells. Tritiated thymidine uptake assay confirmed the antiproliferative effects of FK866 in MM cell lines and patient cells. To examine the mechansim of action, we showed that intracellular NAD+ levels decreased with FK866 treatment at 24 and 48 hours. Furthermore, knock-down of Nampt by small interfering RNAs caused significant inhibition of MM cell growth. FK866 triggered anti-MM activity in our models of MM in the bone marrow (BM) microenvironment, confirming its ability to overcome the proliferative advantage conferred by the BM milieu. FK866 treatment also inhibited angiogenesis via suppression of pivotal MM pathways PI3K/AKT and ERK. In further studies to delineate its mechanisms of action, no activation of apoptosis was observed in treated-cells. Instead FK866 treatment resulted in a marked increase in autophagy, evidenced by autophagic vacuoles in the cytoplasm and proteolitic processing of endogenous LC3-I to LC3-II. FK866 inhibited mTOR signaling and triggered increased formation of EGFP-LC3 punctae, confirming involvement of autophagic cell death. Finally, combined FK866 with bortezomib (CI < 0.6), melphalan (CI < 0.9), and dexamethasone (CI < 0.8), induced synergistic cytotoxicity against MM cells. Conclusion: Our data therefore show a pivotal role of Nampt in MM cell growth, survival and drug resistance. The ability of FK866 to inhibit Nampt activity strongly supports its clinical evaluation to improve patient outcome in MM. Disclosures: Hideshima: Acetylon: Consultancy. Anderson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Acetylon: Membership on an entity's Board of Directors or advisory committees.

Deregulated microRNA (miR)/transcription factor (TF)-based networks represent a hallmark of cancer. We report here a novel c-Myc/miR-23b/Sp1 feed-forward loop with a critical role in multiple myeloma (MM) and Waldenstrom’s macroglobulinemia (WM) cell growth and survival. We have found miR-23b to be downregulated in MM and WM cells especially in the presence of components of the tumor bone marrow milieu. Promoter methylation is one mechanism of miR-23b suppression in myeloma. In gain-of-function studies using miR-23b mimics-transfected or in miR-23b-stably expressing MM and WM cell lines, we observed a significant decrease in cell proliferation and survival, along with induction of caspase-3/7 activity over time, thus supporting a tumor suppressor role for miR-23b. At the molecular level, miR-23b targeted Sp1 3′UTR and significantly reduced Sp1-driven nuclear factor-κB activity. Finally, c-Myc, an important oncogenic transcription factor known to stimulate MM cell proliferation, transcriptionally repressed miR-23b. Thus MYC-dependent miR-23b repression in myeloma cells may promote activation of oncogenic Sp1-mediated signaling, representing the first feed-forward loop with critical growth and survival role in myeloma.

Background: Acute Myeloid Leukemia (AML) is an incurable disease characterized by a highly unstable genome, resulting in large-scale changes at diagnosis, as well as further evolution contributing to disease progression. However, the mechanisms whereby tumor cells adapt to genomic instability are largely unknown, but recent observations have correlated these abnormalities with dysfunctional DNA damage repair (DDR) machinery. SIRT6 is an important regulator of cellular stress response and genomic integrity. Here we investigated the role of this NAD+ -dependent deacetylase in regulating ongoing DNA damage observed in AML patients. Methods: SIRT6 mRNA level was determined by RT-qPCR in AML patients (n=100) diagnosed at the Hematology Department of University of Genoa (Italy), compared with normal bone marrow derived CD34+ cells (n=5). Correlation studies with clinical and molecular characteristics of these patients were also performed. A panel of different AML cell lines and primary cells, both sensitive and resistant to conventional and novel anti-AML therapies, was used in the study. The anti-leukemic effect of DNA-damaging agents (DDAs) including idarubicin, Ara-C and fludarabine was evaluated in presence of SIRT6 depletion/inhibition by CTG assay and Annexin-V/propidium iodide staining. Mechanistic studies were performed with Western-blotting, lentivirus-mediated shRNAs and immunofluorescence assay. Analysis of DNA DSB repair was done using chromosomally integrated reporter constructs, followed by cytometer analysis. Results: AML patients were grouped into lower and higher SIRT6 expressers according to its median mRNA level. Patients with lower expression had a higher incidence of FLT3-ITD (p=0.034, Wilcoxon signed rank test). No significant association was observed with respect to mutations of NPM1, nor with WT1 and BAALC expression. SIRT6 expression correlated also with adverse clinical outcome in term of event free and overall survival (p=0.035 and p=0.025, respectively; unpaired t test). Based on these data, we evaluated SIRT6 role in biology of AML. We found higher SIRT6 protein level in AML cell lines carrying FLT3-ITD mutation (MOLM-14 and MV 4-11) compared to cell lines harboring other mutations (OCI-AML3, THP-1, KG, NB4, HL60, Nomo1 and U937). Targeting SIRT6 by specific shRNAs weakly reduced AML cell survival compared with control-scrambled cells, by impairing DNA repair efficiency. Indeed, a restricted effect of SIRT6 impairment on DNA damage proteins (H2AX, RAD51, 53BP1, RPA32) was measured. We next examined the therapeutic relevance of SIRT6 inhibition in AML by testing effects of its depletion in combination with genotoxic agents. Remarkably, SIRT6 depletion conferred increased sensitivity of AML cells to idarubicin, Ara-C and Fludarabine. Overall, enhancing genotoxic stress while concomitantly blocking DNA double-strand breaks (DSBs) repair response, may represents an innovative strategy to increase chemosensitivity of AML cells. Further mechanistic studies revealed that SIRT6 acts as a genome guardian in leukemia cells by binding DNA damage sites and activating DNA-PKcs and CtIP by deacetylation, which in turn promotes DNA repair. Conclusion: Genomic instability is present in all hematologic malignancies including AML. Strategies aimed to shift the balance towards high DNA damage and reduced DNA repair by SIRT6 inhibition can decrease AML growth and may benefit patients with otherwise unfavorable outcomes. Disclosures No relevant conflicts of interest to declare.

B cell maturation antigen (BCMA), selectively elevated in malignant plasma cells, is an ideal target antigen for immunotherapies for multiple myeloma (MM). Most recently, we reported novel antagonistic anti-BCMA antibody drug conjugates (ADCs) showing potent and specific anti-MM activities via effector cell-dependent and -independent mechanisms in vitro and in vivo (Blood 2014; 123:3128) We here further characterize molecular mechanisms of BCMA activation in MM cells in the bone marrow microenvironment by directly manipulating BCMA receptor levels in MM cells and ligation of a proliferation-inducing ligand (APRIL) to MM cells. Three MM cell lines H929, MM1S, and RPMI8226 with highest, medium, and low BCMA, respectively, were either transfected with lentiviruses of BCMA shRNA or cDNA. First, downregulation of BCMA significantly blocked viability of all 3 MM cells and induced caspase3/7 activities, which led to potent reduction of colony formation in a 3-week methylcellulose culture. Next, MM1R and H929 transfectants with the Doxycyclin (dox)-inducible lentiviral expression vector pTRIPZ shBCMA were generated. Time-dependent BCMA reduction only occurred in dox (1 ug/ml)-containing media. Dox-dependent BCMA inhibition was followed by decreased anti-apoptotic genes (Mcl1, Bcl-2, XIAP, NAIP, NFκB1, NFκB2) and proliferative genes (CCND2, CDK4/6, c-MYC). Conversely, overexpression of BCMA in RPMI8226 by either pCMV6/BCMA vector or pLocBCMA lentiviruses significantly increased NFκB (p65, p50, p52) DNA binding activity. Anti-apoptotic gene and cell proliferation genes were also up-regulated in BCMA-overexpressing MM cells. In addition, osteoclast activation factors MIP-1α/β, SDF-1, angiogenesis factors (VEGF, PECAM-1), adhesion proteins (CD44, ICAM1), as well as immunosuppressive factor TGFβ were augmented in BCMA-overexpressing MM cells. Importantly, opposite effects on these downstream genes were seen in BCMA-knockdown MM cells. Moreover, stimulation of 3 MM cells by APRIL robustly induces NFκB DNA binding activity (p65, p50, and p52, to a lesser extend) and activates PI3K/AKT and ERK1/2 signaling. APRIL also induces pro-survival/anti-apoptotic targets (BCL2A1, NFκB1, NFκB2) and chemotactic/osteoclast activating factors (MIP1α and MIP1β) in a dose-dependent manner. Angiogenesis and adhesion/chemoattractant factors (VEGF, IL-8, CXCL10, and RANTES) were also significantly induced upon APRIL stimulation. In contrast, BCMA-Fc protein that blocks APRIL binding to BCMA, inhibits secretion of these cytokines/chemokines, indicating specific response of engagement of BCMA by APRIL in BCMA-expressing MM cells. APRIL induced adhesion and migration of MM cells whereas BCMA-Fc blocked APRIL-induced responses. Finally, RPMI8226/pLocBCMA cells induce earlier tumor onset and more tumor growth in mouse xenograft model when compared with control RPMI8226 cells. In contrast, pTRIPZ shBCMA H929 cells induce significantly less tumor formation and further prolong survival of mice fed with dox(2 ug/ml)-containing water than those without dox. Together, these results define molecular regulators of active APRIL/BCMA signaling cascade in the MM BM milieu, further supporting targeting APRIL/BCMA in MM. Disclosures Anderson: Celgene: Consultancy; Sanofi-Aventis: Consultancy; Onyx: Consultancy; Acetylon: Scientific Founder, Scientific Founder Other; Oncoprep: Scientific Founder Other; Gilead Sciences: Consultancy.

P21-activated serine/threonine kinase 4 (PAK4) is a major effector of Cdc42 and is essential for cytoskeleton reorganization. PAK4 is activated in cancer cells, promotes cell migration and anchorage-independent cell growth, and protects against apoptosis induction. With cellular migration playing a significant role in multiple myeloma (MM) cell growth and survival, we investigated the expression and subcellular localization of PAK4 in MM cells. We observed a high level of un-phosphorylated PAK4 in the cytoplasm and high levels of phosphorylated PAK4 in the nucleus. In a gain-of-function study, over-expression of PAK4-eGFP in PAK4-deficient MM cells (RPMI8226) significantly increased cell proliferation and survival. Conversely, in a loss-of-function study, conditional knock-down of PAK4 expression with TRIPZ-lentiviral vectors decreased MM cell proliferation and survival proportionally to the reduction in PAK4. With a significant impact of PAK4 on MM cell growth, we identified a class of orally bioavailable PAK4 allosteric modulators (PAMs; e.g. KPT-6604, -7189, -7657, -8752). We observed inhibition of MM cell growth and survival after treatment with PAMs even in the presence of bone marrow microenvironment. In addition, there is a significant correlation between PAK4 expression and the inhibition concentration (IC50s) of PAMs in proliferation assays. Moreover, inhibition of PAK4 induced receptor and mitochondrial-mediated apoptotic pathways via Caspase-3, -8, and -9 activation. PAMs had no significant effect on normal PBMCs, suggesting a favorable therapeutic index in MM treatment. Finally, in two murine models of human myeloma, orally bioavailable KPT-8752 given daily was able to inhibit tumor growth in vivo and prolong overall survival. In summary, PAK4 plays an important cellular and molecular function in myeloma and its inhibition with a new class of PAK4 allosteric modulators provides a novel therapeutic approach for the treatment of MM. Disclosures Senapedis: Karyopharm: Employment. Baloglu:Karyopharm: Employment. Anderson:Celgene: Consultancy; Sanofi-Aventis: Consultancy; Onyx: Consultancy; Acetylon: Scientific Founder, Scientific Founder Other; Oncoprep: Scientific Founder Other; Gilead Sciences: Consultancy.

A proliferation-inducing ligand (APRIL), a close member of B-cell-activating factor (BAFF) belonging to the TNF superfamily, is mainly produced by bone marrow (BM) accessory cells to stimulates growth and survival of multiple myeloma (MM) cells. Unlike BAFF, APRIL is dispensable in B cell homeostasis but more critical in plasma cell differentiation and survival. It has higher affinity than BAFF (nanomolar vs micromolar range) to B cell maturation antigen (BCMA) (nanomolar vs micromolar range) which expresses at high levels in all patient MM cells. APRIL also binds to a common plasma cell (PC) marker syndecan-1 (CD138) to induce signaling cascade via TACI, the other APRIL receptor in PC. We here characterize molecular mechanisms regulating APRIL activation in the BM microenvironment and further determine whether a novel anti-APRIL monoclonal antibody hAPRIL.01A inhibits its functional sequelae in MM. First, in vitro osteoclast and macrophage cultures were performed by stimulating CD14+ monocytes from MM patient samples with M-CSF/RANKL and M-CSF, respectively. Osteoclasts and macrophages secret significantly higher levels of APRIL than unstimulated CD14+ monocytes and BM stromal cells (BMSC), as confirmed by ELISA and qRT-PCR. All MM cell lines express cell surface BCMA in significantly higher level than TACI (p < 9.06e-15). H929 MM cells (expressing only BCMA, but not TACI), and other MM cell lines were next stimulated with APRIL, in the presence or absence of hAPRIL.01 Ab followed by immunoblotting and TaqMan® Array assays on harvested protein lysates and mRNA. APRIL stimulation consistently activated NF-kB, PI3K/AKT, and ERK1/2 signaling in MM cells. Importantly, NF-kB-DNA binding activities of p65 and p50 (p52, to a less extent), were significantly upregulated as early as 15 minute and sustain to 4h in all MM cell lines after stimulation. Conversely, hAPRIL.01 Ab completely blocked these signaling cascades, consistent with significantly decreased NF-kB-DNA binding activities in BCMA-knock-downed MM cells by shBCMA lentivirus transfection. APRIL further induced pro-survival proteins (Mcl1, Bcl2, BIRC3, XIAP) and MM cell growth-stimulating regulators (CCDN2, CDK4, CDK6, c-myc), which were completely inhibited by hAPRIL.01 Ab. These results correlated with blockade of hAPRIL.01 Ab in APRIL-promoted viability and colony formation of MM cells, in the presence of osteoclasts or macrophages. APRIL also induces adhesion of MM cells to BMSC, which was blocked by hAPRIL.01 Ab. This concurred with hAPRIL.01 Ab-reduced adhesion molecules (CD44, ICAM-1) induced by APRIL. APRIL-increased VEGF-A and PECAM-1 in MM cells was also significantly reduced by this mAb. APRIL-upregulated chemotactic/osteoclast-activating factors (MIP-1α, MIP1β, SDF-1) were also inhibited by this Ab. Other angiogenesis and adhesion/chemoattractant factors, i.e., IL-8, CXCL10, RANTES and MDC (ccl22), were changed in a similar fashion, indicating specific blocking of hAPRIL.01 Ab to APRIL-induced downstream target genes. This mAb further inhibited APRIL-increased viability of plasmacytoid dendritic cells (pDC) and diminished MM cell viability protected by pDC in 3-d cocultures. Finally, hAPRIL.01 specifically overcame APRIL-, but not IL-6, induced protection in lenalidomide- or dexamethasone-treated MM1S and H929 MM cells. These studies confirm a constitutive APRIL activation via BCMA and TACI in promoting malignancies of myeloma cells, supporting a novel therapeutics of hAPRIL.01 Ab to target MM in the BM microenvironment. Disclosures van Eenennaam: BioNovion: Employment. Elsas:BioNovion: Employment. Anderson:Celgene: Consultancy; Onyx: Consultancy; Gilead Sciences: Consultancy; Sanofi-Aventis US: Consultancy; Acetylon: Scientific Founder Other; Oncoprep: Scientific Founder Other.

B cell maturation antigen (BCMA), highly expressed on malignant plasma cells in human multiple myeloma (MM), has not been effectively targeted with therapeutic monoclonal antibodies (mAbs). We here investigated the anti-MM activity of J6M0-mcMMAF (GSK2857916), a humanized and afucosylated anti-BCMA antibody-drug conjugate (ADC) via uncleavable linker. This novel antagonist anti-BCMA antibody shows binding against all CD138-expressing MM cell lines and patient MM cells, confirming universal BCMA expression on the surface of myeloma cells. Real-time qRT-PCR also showed significantly upregulated BCMA mRNA in CD138+ cells purified from MM patients vs. normal donors (p < 0.03). In contrast, BCMA is undetectable in CD138-negative cells from MM patients. J6M0-mcMMAF inhibits cell growth and induces caspase 3-dependent apoptosis in both drug-sensitive and -resistant MM cell lines and patient CD138+ MM cells, alone and in co-culture with BMSCs. It strongly blocks colony formation of MM cell lines (ED50 ∼6-70 ng/ml) via induction of G2/M arrest, followed by apoptosis. This ADC does not affect viability of BCMA-negative NK, PBMC, and BMSCs, cultured alone or together, confirming its specific targeting of BCMA-positive MM cells. J6M0-mcMMAF, which has enhanced Fc-receptor binding due to afucosylation, significantly improved autologous antibody-dependent cellular cytotoxicity (ADCC) potency and maximum MM cell lysis against MM patient cells (n=5), when compared to J6M0 with normal Fc. The in vivo efficacy of J6M0-mcMMAF was evaluated in murine subcutaneous xenograft models using NCI-H929 and OPM2 cells, as well as in NK-deficient SCID-beige mice with diffuse human MM bone lesions using MM1Sluc cells. Administration of J6M0-mcMMAF at 4 mg/kg (q3d x 4, ip) completely eliminated NCI-H929 and OPM2 xenograft tumors in all mice which remained tumor-free until the termination of studies at 60 and 100 days, respectively. In the MM1Sluc bone marrow dissemination model, J6M0-mcMMAF eradicates detectable tumors after 2 doses at 0.4 mg/kg (q3d x 9, ip), which resulted in extended survival (p Note: This abstract was not presented at the meeting. Citation Format: Yu-Tzu Tai, Chirag Acharya, Mike Y. Zhong, Michele Cea, Antonia Cagnetta, Patrick A. Mayes, Jenny Craigen, Louise Gliddon, James Smothers, Amanda L. Christie, Andrew L. Kung, Paul Richardson, Nikhil C. Munshi, Kenneth C. Anderson. Novel anti-B cell maturation antigen-monomethyl auristatin F antibody-drug conjugate (GSK2857916) induces potent and selective anti-multiple myeloma activity via enhanced effector function and direct tumor cell killing. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 644. doi:10.1158/1538-7445.AM2014-644

Background Alternative splicing (AS) is a normal epigenetic event with a critical role in the regulation of gene expression. Previous studies showed increased AS in Multiple Myeloma (MM) cells, suggesting the need to assess both expression level of genes and post translational modifications, mediating overall gene function. The NAD-dependent deacetylases Sirtuins (SIRTs), mammalian homologues of the yeast Sir2, modulate various biological processes including metabolism, cell survival, development, chromatin dynamics, or DNA repair. Recent microarray profiling data using newly diagnosed patients with MM, suggests clinical relevance of such deacetylases since their level predicts for both progression free and overall survival. Among SIRTs family membersSIRT-5, SIRT-6 and SIRT-7 transcript levels positively correlated with disease progression (from MGUS to active MM). These studies provide the rationale for further examining the biological processes including epigenetic changes, mutations, or AS events that contribute to aberrant expression of SIRTs in MM. Methods Purified RNA from MM cell lines, newly diagnosed MM patient cells, as well as peripheral blood mononuclear cells (PBMCs) from normal healthy donors was subjected to SIRT expression analysis. Specifically, SIRTs-specific primers were developed and optimized using standard RT-PCR conditions. RNA integrity was confirmed using Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as an endogenous control. Aberrant splicing of SIRT-5, SIRT-6, and SIRT-7 was confirmed by cloning and sequencing, followed by analysis of their expression patterns in MM patients versus normal PBMCs. Results We found that SIRTs genes are frequently miss-spliced in MM patients. To our knowledge, this is the first report showing SIRTs miss-splicing event in MM. Through cloning and sequencing analysis, we identified novel spliced isoforms of SIRT-5, SIRT-6 and SIRT-7; these occurred as a result of aberrant AS within exon-12, exon-4 and and exon-5, respectively. Specifically, exon skipping was noted in SIRT-6 and SIRT-7 variants, via cryptic 5 prime or 3 prime splice sites on exon 12 and/or through partial retention of an intron created SIRT-5 variants. The novel spliced forms were widely expressed in MM cell lines and primary cells, without significance occurrence in normal PBMCs. Our preliminary data show that even though these novel isoforms exhibit reduced deacetylase activity versus full-length variants, this characteristic may impart distinct functional outcome. Finally, in support of above studies, our analysis of MM patient samples suggest that AS among SIRTs is associated with poor clinical outcome in MM patients. Conclusion In the current study, we have identified novel transcript variants of SIRT-5, SIRT-6 and SIRT-7 in MM cells. These aberrant isoforms allow for generating transcripts that encode for dysfunctional proteins, which in turn, may contribute to the genetic heterogeneity in MM. Ongoing studies are delineating the function of these newly identified splice variants of SIRTs and their association with MM progression. Overall, our studies will provide basis for utilizing SIRTs variants as prognostic markers and/or as novel therapeutic targets in MM. Disclosures: Hideshima: Acetylon Pharmaceuticals: Consultancy. Chauhan:Vivolux: Consultancy.

B cell maturation antigen (BCMA), a member of the tumor necrosis factor receptor superfamily (TNFRSF17), is selectively induced during plasma cell (PC) differentiation and is commonly expressed at high levels in malignant PCs. Using real time RT-PCR, we here first showed that BCMA mRNA was upregulated in CD138+ PCs from MM patients compared to normal healthy donors (p Disclosures: Tai: Onyx: Consultancy. Richardson:Millennium: Membership on an entity’s Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees. Anderson:celgene: Consultancy; onyx: Consultancy; gilead: Consultancy; sanofi aventis: Consultancy; oncopep: Equity Ownership; acetylon: Equity Ownership.

Genomic instability is a hallmark of several types of solid and hematologic malignancies, including multiple myeloma (MM). Although structural and numerical chromosomal abnormalities are common features of MM cells, the underlying molecular basis of MM genomic instability is still largely unknown. To this aim, we have investigated the activity of non-homologous end joining (NHEJ), which represents the most important mechanism of double-strand breaks (DSBs) repair, in MM cells. First, we developed and validated a dual gene plasmid-based assay utilizing Luciferase (LUC) as a test gene which measures end joining, and Alkaline Phosphatase (SEAP) as a reporter gene to control for transfection efficiency, in either intact cells (in vivo assay) or in cell free extracts (in vitro assay). The first one is a chemiluminescent assay which allows for direct measurement of LUC and SEAP in the supernatant of the cells 24h after electroporation with the plasmid, while the cell free extract method is a customized TaqMan® approach based on a quantitative evaluation of the plasmid rejoining. Both assays revealed a significant increase in NHEJ in all 6 MM cell lines tested compared to normal peripheral blood mononuclear cells (PB-ND) and bone marrow stromal cells (BMSC). We further confirmed the hyper-activation of the NEHJ pathway by analyzing the binding activity of ku86, a key NHEJ-related protein involved in the recognition of the broken DNA ends and in the initiation of the DSBs repair process. Six out of 9 MM cell lines showed a significant increase in ku86-binding activity respect to normal cells. We also found a higher phosphorylation at Ser 2056 of DNA-PK, a ku86-partner whitch plays a key role in NHEJ. Next, we evaluated the NHEJ activity in 35 patient samples using the cell free assay. Interestingly, level of NHEJ activity divided patients into two different groups: one with an NHEJ activity similar to normal cells and the other to the MM cell lines. Preliminary correlation analysis between NHEJ activity and the clinical features of the patients indicated that the MGUS and Smoldering MM subgroup fall into the normal cluster while relapsed/refractory disease to the cell lines one. Finally, using the French (IFM) and the Arkansas (GSE2658) dataset, we demonstrate a significant association between NHEJ pathway-related gene expression and overall survival by the Globaltest analysis. We were also able to find a common NHEJ signature of 6 genes whose expression significantly correlates with patient survival in both the datasets. In conclusion, our data indicate an aberrant activation of NHEJ in MM, highlighting its role in the progression of the disease and suggesting this pathway as an important new prognostic marker in myeloma. Disclosures: No relevant conflicts of interest to declare.

Background Deregulation of the DNA damage response (DDR) signaling machinery underlies genomic instability, leading to cancer development and clonal evolution. Multiple Myeloma (MM) remains an incurable disease characterized by a highly unstable genome, with aneuploidy observed in nearly all patients. The mechanism causing this karyotypic instability is largely unknown, but recent observations have correlated these abnormalities with dysfunctional DDR machinery. Mammalian NAD+-dependent deacetylase sirtuin-6 (SIRT6) is emerging as new protein involved in multiple pathways, including maintenance of genome integrity. Methods A panel of 18 MM cell lines, both sensitive and resistant to conventional and novel anti-MM therapies, was used in this study. Blood and BM samples from healthy volunteers and MM patients were obtained after informed consent and mononuclear cells (MNCs) separated by Ficoll-Paque density sedimentation. Patient MM cells were isolated from BM MNCs by CD138-positive selection. Lentiviral delivery was used for expression and knock-down of SIRT6 in MM cell lines. The biologic impact of SIRT6 phenotype was evaluated using cell growth, viability and apoptosis assays. DNA Double-Strand Breaks (DSB) repair occurring via homologous recombination (HR) or non-homologous end-joining (NHEJ) pathways was assessed using a transient direct repeat (DR)-GFP/I-SceI system. Results A comparative gene expression analysis of 414 newly-diagnosed uniformly-treated MM patients showed high levels of SIRT6 mRNA in MM patients versus MGUS or normal donors; moreover, in active MM elevated SIRT6 expression correlated with adverse clinical outcome. Due to its prognostic significance, we further evaluated its role in MM biology. We found higher SIRT6 nuclear expression in MM cell lines and primary cells compared to PBMCs from healthy donors. Targeting SIRT6 by specific shRNA increased MM cell survival by reducing DNA repair efficiency (HR and NHEJ). Whole genome profiling of three different SIRT6 knockout (Sirt6-/-) MM cell lines identified a restricted effect of SIRT6 silencing on transcription of DNA damage genes, which also represented the most down-regulated genes. Consistent with these data, GSEA algorithm revealed that gene set regulating DNA repair were prominently enriched in SIRT6 depleted cells (p Conclusion Collectively, our data provide basis for targeting SIRT6 as a novel therapeutic strategy in combination with genotoxic agents to enhance cytotoxicity and improve patient outcome in MM. Disclosures: Tai: Onyx: Consultancy. Hideshima:Acetylon Pharmaceuticals: Consultancy. Chauhan:Vivolux: Consultancy. Anderson:celgene: Consultancy; onyx: Consultancy; gilead: Consultancy; sanofi aventis: Consultancy; oncopep: Equity Ownership; acetylon: Equity Ownership.

Transcription factors (TFs) are important oncogenic regulator and are altered during tumor initiation and progression. Our oncogenomic analysis of gene expression data from large clinically-annotated patient samples identified TF Dp1 as one of the most important gene affecting both overall and event-free survival in multiple myeloma (MM). Elevated Dp1 expression was predictive of adverse clinical outcome, independent of Dp1 protein partners, E2Fs and RB, suggesting direct impact of Dp1 and providing the rationale to further evaluate its specific role in MM. We have observed high level of Dp1 expression and activity in MM cells which was further induced after interaction with bone marrow stromal cells (BMSC). Moreover, Dp1 knock-down using specific sh-RNA decreased MM cell growth in 5 MM cell lines with different genetic background, with a concomitant G1 arrest and late induction of apoptosis. These data suggest a role for Dp1 in MM cell proliferation and survival and established a rationale to identify its molecular impact. We have further characterized Dp1 activity using chromatin immunoprecipitation with Dp1 or E2F1 specific antibody followed by genome wide sequencing (ChIP-Seq) to identify Dp1-binding regions in MM. We have identified 2783 exclusive Dp1 binding regions in two MM cell lines. Examination of Dp1 and E2F1 binding revealed that Dp1 co-occupies 65% of the binding sites with E2F1. The DAVID gene set enrichment analysis showed that identified genes were related to cell cycle, as well as to transcriptional and translational processes. To assess the functional consequences of Dp1 DNA binding, the ChIP-Seq data were supplemented with gene expression profile of MM1S cells following shRNA-mediated Dp1 and E2F knock-downs. Integrated analysis incorporating ChIP-seq and expression data identified Dp1 response program in MM. 805 (46%) of 1752 differentially expressed genes also have binding sites for Dp1 and likely are direct transcriptional targets of Dp1 in MM. Enrichment analysis of direct targets revealed that the most strongly enriched pathways for both Dp1 and E2F1 genes combined were related to the cell cycle, especially DNA replication, repair, and metabolism. Interestingly, pathway analysis identified ‘‘regulation of RNA metabolic processes’’ (40 target genes), ‘‘RNA processing’’ (93 target genes) ‘‘RNA splicing’’ (95 genes), and ‘‘RNA binding’’ (53 genes) as statistically significant RNA-related categories enriched among Dp1 target genes, suggests role of Dp1 in RNA splicing. Based on our previous data showing that dysregulated alternate splicing (AS) has significant impact on overall clinical outcome MM, we evaluated the expression of Dp1-modulated splicing factors in our clinically annotated cohort of MM patients and 5 normal PCs. We identified 23 SFs upregulated in MM compared to normal plasma cells. Importantly, the increased expression of 12 of these SFs was linked with poor prognosis in this cohort of myeloma patients. Our data show for the first time that SFs are upregulated in myeloma and link to clinical outcome. To evaluate the impact of Dp1 on alternate splicing (AS), we performed genome-wide analysis of alternate splicing in total RNA from Dp1 silenced MM1S cells using Human Exon1 ST arrays. Splicing profiles showed that Dp1 knock down causes widespread changes in AS. We have identified 3683 genes whose one exon has splicing index more than 1.5 in in shDP1 compared to control pLKO.1-transduced MM1S cells, suggesting impact of Dp1 silencing on alternate splicing. We are now evaluating impact of a peptide able to disrupt Dp1-E2F1 binding with consequent effect on MM cell growth and alternate splicing. In conclusion, our investigation showed that the Dp1/E2F1 signaling pathway plays significant role in myeloma and can directly activate transcription of specific SFs with effect on alternate splicing and potential functional, clinical and therapeutic implications in myeloma. Disclosures: No relevant conflicts of interest to declare.

The key nuclear export protein CRM1 (chromosomal region maintenance 1, Exportin 1, XPO1) may directly contribute to the pathophysiology of human multiple myeloma (MM). Here, we characterized the role of CRM1 in MM biology and defined the efficacy and molecular mechanisms of novel oral, irreversible, selective inhibitors of nuclear export (SINEs) targeting CRM1 against MM. CRM1 is significantly elevated in patient MM vs. normal plasma cells at transcript and protein levels. CRM1 downregulation by shCRM1 lentiviruses inhibited cell growth and survival of MM cells (p< 0.01). Importantly, SINEs (KPT-185, KPT-251, KPT-276, and KPT-330) blocked proliferation and decreased survival of MM cell lines and patient MM cells (LD50 2-log differences). SINEs potently enhanced nuclear accumulation of multiple CRM1 cargo tumor suppressor proteins, including rapid induction of p53 and IκB (as early as 2h after drug treatment) followed by FOXO1A, FOXO3A, p27, and PP2A in MM cells. Transcripts of p53 and its downstream targets (p21, PUMA, BAX) were induced by KPT-185, thereby inducing strong growth arrest and apoptosis. KPT-185 decreased MM oncogenes (c-myc, c-maf), anti-apoptosis molecules Mcl-1 and Bcl-xL; increased pro-apoptotic protein BAX; as well as inhibited pIκBα. Inhibition of pIκBα further correlated with KPT-185-blocked NFκB p65 DNA-binding activity in MM cells with or without A Proliferation-Inducing Ligand (APRIL) stimulation. KPT-185 further downregulated CRM1 protein, which was blocked by bortezomib; concurrently, KPT-185 (or KPT-330) upregulated CRM1 mRNA in MM cells. Cleavage of caspase 3 and PARP was markedly increased in MM1R cells treated with KPT-185 and bortezomib vs. either drug alone, confirming enhanced cytotoxicity by combination of these agents. Combined dex with KPT-185 (or KPT-276) induced synergistic cytotoxicity against MM cells (combination indices < 1). Moreover, KPT-185 and KPT-330 impaired osteoclastogenesis and bone resorption via blockade of RANKL-induced NFκB activation and NFATc1 in OC precursor cells, without impacting osteoblasts and BMSCs. Finally, SINEs (KPT-251 and KPT-276) suppressed MM cell growth (p< 0.01), diminished MM cell-induced osteolysis, and prolonged survival of SCID mice with diffuse human MM bone lesions. Together, these results identify CRM1 as a promising novel target in MM, strongly supporting clinical development of SINE CRM1 inhibitors to inhibit both MM cell growth and related bone disease. The oral SINE KPT-330 is ongoing in MM and other hematological malignancies. Citation Format: Yu-Tzu Tai, Yosef Landesman, Chirag Acharya, Yolanda Calle, Mike Zhong, Michele Cea, Daniel Tannenbaum, Antonia Cagnetta, Michaela Reagan, Aditya Munshi, William Senapedis, Jean-Richard Saint-Martin, Trinayan Kashyap, Sharon Shacham, Michael Kauffman, Yumei Gu, Lizi Wu, Steve Schey, Irene Ghobrial, Andrew Kung, Nikhil Munshi, Paul Richardson, Kenneth Anderson, Haoqiang Ying. The nuclear export protein CRM1 (XPO1) regulates multiple myeloma cell growth, osteoclastogenesis, and myeloma-induced osteolysis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2142. doi:10.1158/1538-7445.AM2013-2142

Abstract 326 The key nuclear export protein CRM1 (chromosome region maintenance 1, Exportin 1, XPO1) may directly contribute to the pathophysiology of human multiple myeloma (MM). Here, we characterized the role of CRM1 in MM biology and defined molecular mechanisms whereby novel oral, irreversible, selective inhibitors of nuclear export (SINE) targeting CRM1 mediate anti-MM activity. CRM1 gene expression is increased with disease progression, since it is significantly elevated in active MM and plasma cell leukemia (PCL) vs. normal/MGUS/SMM patients (p< 0.02). CRM1 downregulation by shCRM1 lentiviruses significantly decreases MM cell viability regardless of drug sensitivity and p53 status. Importantly, SINE (KPT-185, KPT-251, KPT-276, and KPT-330) specifically blocked proliferation and decreased survival of MM cell lines (n=14) and patient MM cells (n=17) (LD50 < 200 nM), cultured alone and with bone marrow stromal cells (BMSCs) or osteoclasts. Caspases 3, 8, and 9 were not induced by any SINE in BMSCs derived from MM patients, cultured either alone or with MM cells, under conditions inducing marked apoptosis of MM cells (>2-log differences). These agents potently enhanced nuclear accumulation of multiple CRM1 cargo tumor suppressor proteins p53, IκB, FOXO1A, FOXO3A, p27, and PP2A in MM cells. Transcripts of p53 and its downstream targets p21, PUMA, BAX were also induced by KPT-185, thereby inducing strong growth arrest and apoptosis. KPT-185 decreased MM oncogenes (c-myc, c-maf), anti-apoptosis molecules Mcl-1 and BCL-xL; increased pro-apoptotic protein BAX; as well as inhibited HSP70 and pIkBa. KPT-185 further blocked baseline and APRIL-induced NFkB p65 DNA-binding activity in MM cells. It triggered proteasome-dependent reduction of CRM1 protein; concurrently, KPT-185 and KPT-330 upregulated CRM1 mRNA. Furthermore, KPT-185 induced a number of tumor suppressing, regulatory, apoptotic and anti-inflammatory genes, i.e., p53, p21, PUMA, BAX, CHOP, C10orf10, MIC1, IκBα in MM1S cells in a dose-dependent manner, regardless of the presence of BMSCs. Cleavage of caspase 3 and PARP was markedly increased in MM1R cells treated with KPT-185 and bortezomib vs. either drug alone, validating that the combination of these agents triggered stronger cytotoxicity against MM cells. Combined treatment with dex and KPT-185 (or KPT-276) induced synergistic cytotoxicity against MM cells. Moreover, KPT-185 and KPT-330 impaired osteoclastogenesis and bone resorption via blockade of RANKL-induced NFκB activation in osteoclast precursor cells, without impacting osteoblasts and BMSCs (Abstract#48190). Importantly, SINEs (KPT-251 and KPT-276) suppressed MM cell growth (p< 0.01), diminished MM cell-induced osteolysis, and prolonged survival of SCID mice with diffuse human MM bone lesions (p=0.0004). Together, these results identify CRM1 as a promising novel target in MM, strongly supporting clinical development of SINE CRM1 antagonists to inhibit both MM cell growth and related bone disease. Disclosures: Landesman: Karyopharm Therapeutics Inc: Employment. Senapedis:Karyopharm Therapeutics Inc: Employment. Saint-Martin:Karyopharm Therapeutics Inc: Employment. Kashyap:Karyopharm Therapeutics Inc: Employment. Ying:Karyopharm Therapeutics Inc: Employment. McCauley:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. Munshi:Celgene: Consultancy; Millenium: Consultancy; Merck: Consultancy; Onyx: Consultancy. Richardson:Millenium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene, Millennium, BMS, Onyx: Membership on an entity's Board of Directors or advisory committees; Acetylon, Oncopep: Scientific Founder, Scientific Founder Other.

Abstract 723 Background: Multiple myeloma (MM) is a clonal malignancy of plasma cells with hallmark genetic instability resulting in large-scale changes at diagnosis, as well as further evolution contributing to disease progression. Inhibition of DNA repair mechanisms leads to significant reduction in acquisition of new genetic changes and associated progression of MM. Mammalian sirtuins are class III NAD+-dependent deacetylases emerging as innovative proteins involved in multiple pathways, including genome maintenance. Methods: A panel of 18 MM cell lines, both sensitive and resistant to conventional and novel anti-MM therapies, was used in the study. The antitumor effect of a pan-sirtuins inhibitor, Nicotinamide (Nam), alone and combined with DNA-damaging agents, was investigated by CTG assay and Annexin-V/propidium iodide staining. Mechanistic studies were performed with thymidine incorporation, Western-blotting, lentivirus-mediated shRNAs and immunofluorescence assay. Analysis of DNA DSB repair was done using chromosomally integrated reporter constructs, followed by cytometer analysis. Results: We analyzed an Affymetrix GeneChip (GSE6477) array of patient MM cells (n=162) compared with normal plasma cells, and found that transcript levels of two nuclear sirtuins (SIRT6 and SIRT7) were significantly higher in monoclonal gammopathy of undetermined significance (MGUS), smoldering MM, active MM, and relapsed MM compared with normal plasma cells. Importantly, protein analysis confirmed increased nuclear levels of these deacetylases in MM cell lines, including those resistant to DNA-damaging agents (MM.1R, LR-5, Dox40), as well as in patient CD138+ MM cells compared to PBMCs from healthy donors. Next we evaluated the functional role of these Sirtuins in MM cells by using loss of function approaches with RNAi. SIRT6 and SIRT7 silencing by knockdown reduced MM cell proliferation compared with control scrambled cells, with only a modest induction of cytotoxicity. We also examined the effects of Nam on DNA-damage response signaling triggered by conventional anti-MM agents melphalan and doxorubicin. Nam treatment did not appreciably affect MM cell viability; however, pretreatment with Nam impaired DNA double-strand breaks (DSBs) repair as well as DNA repair mechanisms triggered by conventional DNA damaging agents, evidenced by γH2AX and RPA phosphorylation, respectively. Consistent with these findings, Nam-pretreated MM cells formed fewer RAD51 foci in response to Doxorubicin and Melphalan, thereby conferring sensitivity to these agents. Importantly, this sensitizing effect was also observed in MM cells resistant to doxorubicin (RPMI-Doxo40) or melphalan (LR5), indicating that Nam increases chemosensitivity in both drug-sensitive and –resistant MM cells. Similarly, lentivirus-mediated shRNA knockdown of SIRT-6 and −7 sensitized MM cells to melphalan and doxorubicin. Finally, both chemical and genetic approaches improved the efficiency of DNA DSB repair mechanisms (Homologous and non-Homologous end-joining Recombination) in MM cell lines containing chromosomally integrated green fluorescent protein-based reporter constructs. Ongoing in vivo experiments are assessing how the chemical susceptibility of SIRT6 and/or 7-deficient cells can be exploited therapeutically. Conclusion: Our study demonstrates a link between nuclear sirtuins and DNA instability in MM cells, providing the basis for incorporation of inhibitors of these SIRTs into innovative anti-MM therapeutic approaches. Disclosures: Munshi: Celgene: Consultancy; Millenium: Consultancy; Merck: Consultancy; Onyx: Consultancy.

Abstract 330 Background: Our previous study demonstrated that inhibition of nicotinamide phosphoribosyltransferase (Nampt) acts by severely depleting intracellular NAD+ content and thus eliciting mitochondrial dysfunction and autophagic MM cell death. The proteasome inhibitor Bortezomib induces anti-MM activity by affecting a variety of signaling pathways. However, as with other agents, dose-limiting toxicities and the development of resistance limit its long-term utility. Here, we demonstrate that combining Nampt inhibitor and bortezomb induces synergistic anti-MM cell death both in vitro using MM cell lines or patient CD138+ MM cells and in vivo in a human plasmacytoma xenograft mouse model. Material and Methods: We utilized MM.1S, MM.1R, RPMI-8226, and U266 human MM cell lines, as well as purified tumor cells from patients relapsing after prior therapies. Cell viability and apoptosis assays were performed using Annexin V/PI staining. Intracellular NAD+ level and proteasome activity were quantified after 12, 24, and 48h exposure to single/combination drugs by specific assays. In vitro angiogenesis was assessed by Matrigel capillary-like tube structure formation assay. Immunoblot analysis was performed using antibodies to caspase-8, caspase-9, caspase-3, PARP, Bcl-2, and tubulin. CB-17 SCID male mice (n = 28; 7 mice/EA group) were subcutaneously inoculated with 5.0 × 106 MM.1S cells in 100 microliters of serum free RPMI-1640 medium. When tumors were measurable (3 weeks after MM cell injection), mice were treated for three weeks with vehicle alone, FK866 (30mg/kg 4 days weekly), Bortezomib (0.5 mg/kg twice weekly), or FK866 (30 mg/kg) plus Bortezomib (0.5 mg/kg). Statistical significance of differences observed in FK866, Bortezomib or combination-treated mice was determined using a Student t test. Isobologram analysis was performed using “CalcuSyn” software program. A combination index < 1.0 indicates synergism. Results/Discussion: Combining FK866 and Bortezomib induces synergistic anti-MM activity in vitro against MM cell lines (P Disclosures: Munshi: Celgene: Consultancy; Millenium: Consultancy; Merck: Consultancy; Onyx: Consultancy.

Abstract 2913 CRM1 (chromosomal region maintenance 1, XPO1) is the major export protein regulating degradation of key tumor suppressors by transporting them from nucleus to cytoplasm, thus abrogating their function. Highly expressed CRM1 is associated with poor prognosis in several solid tumors, and inhibition of CRM1 restores function of tumor suppressors such as p53, p21 and FOXO and IκB (cellular antagonist of NF-κB). Furthermore, CRM1 knockdown enhances sensitivity of human multiple myeloma (MM) cell lines to topoisomerase II inhibitor (Cancer Res 2009 :69, 17). In this study, we investigated a novel selective CRM1 inhibitor, KPT-185, in human MM cells. Gene expression profiling analysis using GEO database showed that CRM1 expression is significantly increased in CD138+ cells from MM patients versus monoclonal gammopathy of undetermined significance (MGUS) patients or normal donors (p Disclosures: Landesman: Karyopharm Therapeutics: Employment. Senapedis:Karyopharm Therapeutics: Employment. Shacham:Karyopharm Therapeutics Inc.: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. McCauley:Karyopharm Therapeutic Inc.: Employment. Saint-Martin:Karyopharm Therapeutics Inc: Employment. Munshi:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees. Richardson:Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Acetylon: Membership on an entity's Board of Directors or advisory committees.

Abstract 883 Specific expression of Bruton's tyrosine kinase (Btk) in osteoclasts (OC), but not osteoblasts (OB), suggests its role in regulating osteoclastogenesis. Although Btk is critical in B cell maturation and myeloid function, it has not been characterized in plasma cell malignancies including multiple myeloma (MM) and Waldenström Macroglobulinemia (WM). We here investigate effects of PCI-32765, an oral, potent, and selective Btk inhibitor with promising clinical activity in B-cell malignancies, on OC differentiation and function within MM bone marrow (BM) microenvironment, as well as on MM and WM cancer cells. We further define molecular targets of Btk signaling cascade in OCs and MM in the BM milieu. In CD14+ OC precursor cells, RANKL and M-CSF stimulate phosphorylation of Btk in a time-dependent fashion; conversely, PCI-32765 abrogates RANKL/M-CSF-induced activation of Btk and downstream PLCγ2. Importantly, PCI-32765 decreased number of multinucleated OC (>3 nuclei) by tartrate-resistant acid phosphatase (TRAP) staining and the secretion of TRAP5b (ED50 = 17 nM), a specific mature OC marker. It increased size of OCs and number of nuclei per OC, with significantly defective bone resorption activity as evidenced by diminished pit formation on dentine slices. Moreover, lack of effect of Dexamethasone on OC activity was overcome by combination of Dexamethasone with PCI-32765. PCI-32765 significantly reduced cytokine and chemokine secretion from OC cultures, including MIP1α, MIP1β, IL-8, TGFβ1, RANTES, APRIL, SDF-1, and activin A (ED50 = 0.1–0.48 nM). It potently decreased IL-6, SDF-1, MIP1α, MIP1β, and M-CSF in CD138-negative cell cultures from active MM patients, associated with decreased TRAP staining in a dose-dependent manner. In MM and WM cells, immunoblotting analysis confirmed a higher Btk expression in CD138+ cells from majority of MM patients (4 out of 5 samples) than MM cell lines (5 out of 9 cell lines), whereas microarray analysis demonstrated a higher expression of Btk and its downstream signaling components in WM cells than in CD19+ normal bone marrow cells. PCI-32765 significantly inhibits SDF-1-induced adhesion and migration of MM cells. It further blocked cytokine expression (MIP1a, MIP-1β) at mRNA level in MM and WM tumor cells, correlated with inhibition of Btk-mediated pPLCγ2, pERK and NF-kB activation. Importantly, PCI-32765 inhibited growth and survival triggered by IL-6 and coculture with BM stromal cells (BMSCs) or OCs in IL-6-dependent INA6 and ANBL6 MM cells. Furthermore, myeloma stem-like cells express Btk and PCI-32765 (10–100 nM) blocks their abilities to form colonies from MM patients (n=5). In contrast, PCI-32765 has no adverse effects on Btk-negative BMSCs and OBs, as well as Btk-expressing dendritic cells. Finally, oral administration of PCI-32765 (12 mg/kg) in mice significantly suppresses MM cell growth (p< 0.03) and MM cell-induced osteolysis on implanted human bone chips in a humanized myeloma (SCID-hu) model. Together, these results provide compelling evidence to target Btk in the BM microenvironment against MM and WM., strongly supporting clinical trials of PCI-32765 to improve patient outcome in MM and WM. Disclosures: Chang: Pharmacyclics Inc: Employment. Buggy:Pharmacyclics, Inc.: Employment, Equity Ownership. Elias:Pharmacyclics Inc: Consultancy. Treon:Millennium: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Genentech: Honoraria. Richardson:Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Munshi:Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Anderson:Millennium Pharmaceuticals, Inc.: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Onyx: Consultancy; Merck: Consultancy; Bristol-Myers Squibb: Consultancy; Actelion: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Abstract 1215 Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder characterized by the expansion of a Leukemic Stem Cell (LSC) clone carrying a Philadelphia translocation, which outgrows the non-malignant haematopoietic stem cells. The tyrosine kinase inhibitors (TKIs) imatinib, nilotinib and dasatinib, are the gold standard for CML treatment since each one shows an impressive rates of complete cytogenetic and molecular response in chronic phase (CP) CML. However the major problem concerning the final efficacy of TKIs therapy is that the majority of responding CP CML patients have detectable BCR-ABL transcripts which might arise from a population of quiescent CML LSC not effectively targeted by TKIs. Therefore the molecular monitoring not always provide a sufficiently precise evaluation of patients to allow the appropriate choice of clinical interventions. Accordingly, it is necessary to monitor the appearance and increase of LSCs to identify and to treat quickly the fundamental responsible for relapse. Thus, we focused Hedgehog (Hh) signalling which has been proved essential for maintenance of cancer stem cells in myeloid leukaemia. Notably recent studies reported that the expansion of BCR-ABL positive leukemic stem cell is dependent on Hh pathway activation. Here, we analyzed the mRNA levels of Smoothened (SMO), a seven-transmembrane domain receptor protein, and Ptch1, a surface receptor regulator of SMO, in 20 CP-CML patients (8 High, 4 Intermediate and 8 Low Sokal Risk respectively) at diagnosis and during the follow-up. Using RT-PCR, in diagnosis setting, we proved that 60% of patients (bone marrow samples) showed Hh signalling significantly activated compared to CD34+ cells from healthy donors. In detail 75% (6/8) of High Sokal Risk CML patients showed an up-regulation of Smo and a down-regulation of Ptch1 mRNA levels, suggestive of active Hh signalling at diagnosis. Conversely Low and Intermediate Sokal Risk CML patients did not show features of Hh activation. Finally we monitored, during the follow-up, the mRNA levels of Smo and Ptch1 together with BCR-ABL to assess the kind of relationship between these parameters. Interestingly we noticed a direct correlation between the increase of BCR-ABL mRNA levels and signs of Hh activity (Smo mRNA increase level and Ptch1 mRNA decrease level). Characteristically, molecular monitoring highlighted that all patients developing resistance to TKIs treatment, showed a tendency to Hh activation (high and low mRNA levels of Patch1 and Smo respectively) few months before the development of Abl KD mutation (10/10). Typically this last behaviour was more evident in patients developing the gatekeeper mutation T315I. Finally, in accordance with published data, we noted that the pharmacological inhibition of Hh signalling impairs the growth of TKIs resistant human CML cell line BaF/T315I, suggesting a novel treatment option. All our data provide molecular evidence for a role of the stemness pathway to predict quickly both the relapse and the TKIs resistance during CML treatment. Therefore, we propose to use Ptch1 and Smo mRNA levels together with BCR-ABL for the molecular monitoring of CP CML. Disclosures: No relevant conflicts of interest to declare.

Abstract 4404 Cancer cells almost invariably exhibit aberrant histone deacetylase (HDAC) activity leading to changes in chromatine structure, altered gene expression, poor differentiation, impaired apoptosis and increased proliferation. Accordingly, virtually all the HDAC inhibitors currently available show some degree of antitumor activity in preclinical cancer models and several of these compounds are currently under investigation or already approved for the treatment of human malignancies. Such is the case of the hydroxamic acid derivative suberoylanilide hydroxamic acid (Vorinostat, Zolinza), approved for the treatment of cutaneous T cell lymphomas. Sirtuins are a large family of deacetylases characterized by a unique, NAD+-dependent enzymatic mechanism. In addition to their established role in metabolism and longevity, recent evidence points to an emerging role for sirtuins in carcinogenesis. In the attempt to identify drug combinations that would increase the activity of traditional HDAC inhibitors we have explored the combination of valproic acid (VA) and butyrate (BU) with the sirtuin inhibitors cambinol and sirtinol in primary B-cell chronic lymphocytic leukemia (B-CLL) cells (n=35), acute myelogenous leukemia (AML) cells (n=10) and leukemia cell lines. Cell viability was assessed by propidium iodide staining and flow cytometry. Combination indices were determined using the median-effect method. In leukemia cells, exposure to sirtuin inhibitors synergistically increased VA and BU mediated cytotoxicity. Conversely, these drugs were poorly active and failed to show any cooperation in healthy cells, including peripheral blood mononuclear cells and fibroblasts, suggesting a cancer-specific mode of action. Similar results were obtained by combining VA or BU with the Nampt inhibitor APO866, which reduces intracellular NAD+ levels and thereby prevents sirtuin activity. Remarkably, SIRT1 and SIRT6 inhibition per se did not seem to account for cell demise upon HDAC inhibition since expression of a dominant negative SIRT1 isoform or RNA interference-mediated SIRT6 silencing failed to increase VA and BU activity. Our data indicate a specific requirement by leukemia cells for sustained sirtuin activity when classical HDACs are inhibited. This feature is suitable to be therapeutically exploited by combining sirtuin inhibitors or APO866 with classical HDAC inhibitors especially for the treatment of hematological malignancies. Disclosures: No relevant conflicts of interest to declare.

Abstract 4675 The prognostic value of WT1 expression at diagnosis is still controversial. It has been retrospectively evaluated in 99 consecutive non pretreated non M3 AML patients who had undergone a complete prognostic work up at diagnosis and had received intensive chemotherapy. Biological markers were evaluated on fresh marrow samples collected at diagnosis. WT1 expression was evaluated using TaqMan Gene Expression Assays as described. All patients received induction therapy with combination of fludarabine, Ara-C and anthracycline ± low dose gemtuzumab ozogamicin (n. 59) or with a conventional combination of Ara-C and anthracycline (n. 40) A conventional post-induction chemotherapy including intermediate dosage Ara-C was administered to all responding patients. Univariate comparisons between patients in CR vs non CR were performed using chi-square analysis or Fisher's exact test for categorical variables and t-test for continuous variables. P values < 0.05 were considered statistically significant. Analyses were performed using SPSS. The prognostic impact of WT1 expression was evaluated using quartiles as cut off point and selecting the one with the lowest p value. The event free survival and OS were calculated using the Kaplan Meier method. Non CR after the first induction course, relapse and death due to any cause were considered events. OS and EFS duration were calculated from start of treatment. The impact of multiple predictor variables was assessed by multivariate analyses according to the Cox regression model for OS and EFS while for the evaluation of RC was used the Logistic regression model. Median age of patients was 59 years (range 17-81). Cytogenetic alterations were prognostically favorable in 3 patients and belonged to the intermediate prognostic group in 77 patients (normal karyotype in 75 patients and +8 in two). Nineteen patients had a poor prognosis cytogenetics. For statistical analyses we considered two karyotipic groups: unfavorable (19 patients) and not unfavorable (80 patients). CRs were 60/99 (60%), of which 40 in 51 patients aged 60 or less (78%) and 20 in 48 older than 60 years (41%). Twenty-six patients relapsed, 54 are alive, 45 have died, with a median follow up of 360 days (range 20-2300). In Table 1 are reported clinical indicators of outcome being patients grouped according to the percentile of WT1 expression with the lowest p value (75th). Statystical analysis showed that all WT1 quartiles were balanced for other prognostic factors, such as cytogenetics, BAALC expression, FLT3 and NPMA and B mutations, age, blast count and therapy. The lack of consense on the role of WT1 level at diagnosis in the prognostic stratification indicate that further clinical studies are required. The clear correlation between the level of WT1 transcript and the tumor burden explains why WT1 is used in the follow up of leukemic patients as universal marker of residual disease, also in patients with specific chimeric products. On the contrary, the biological explanation of the prognostic impact of WT1 transcript level at diagnosis remains uncertain. Over the years WT1 gene has been considered as an oncogene or a tumor suppressor gene. In our experience the protective influence of high WT1 expression cannot be explained with an association with good prognosis biological features (such as mut NPM and / or low BAALC). The positive prognostic value of high WT1 expression might be implicated either with WT1 antioncogenic function, or with the stimulating effect of WT1 oncogene on leukemic cellular cycle, possibly associated with an enhanced response to chemotherapy.Table 1WT1 2400 N./N.pts (%)p univ,p multiv.*RR (95% CI)CR (all karyotypes)41/ 75 (54)19/24 (82)0,0260.063.364 (0.927-12.202)CR (int/good karyot.)36/59 (61)19/210.010,0276.649 (1.240-35.645)CR (denovo AML int kar)31/45 (69)14/15 (98)0.020,03412.557 (1.218-129.446)CR (denovo, N.K.)26/40 (65)15/16 (94)0.0250.0413.430 (1.111-162.318)EFS at 24 months (all karyotypes)8%6%0.0020.050.486 (0.235-1.007)EFS at 24 months (int / good karyot.)9%64%0.0010.0230.360 (0.150-0.866)EFS at 24 months (de novo, N.K.)5%70%0.0010.0070.227 (0.077-0.671)OS (all karyot)15%55%0,110,660.837 (0.371-1.890)OS (int/good kar.)18%63%0,050,180.507 (0.186-1.381)Table 1 legend: * for multivariate analysis age, karyotype, FLT3, NPM mutation, BAALC expression, denovo/secondary disease were considered. Disclosures: No relevant conflicts of interest to declare.

NAD + biosynthesis through nicotinamide phosphoribosyltransferase (NAMPT) holds potential as a target for the treatment of inflammatory disorders due to NAD + ’s role in immune cell signaling and metabolism. In addition to its activity as an enzyme, NAMPT is also secreted in the extracellular space where it acts as a pro-inflammatory and proangiogenic cytokine. NAMPT inhibition with FK866 has anti-inflammatory activity in different models of immune disorders and it prevents ischemia-reperfusion-induced heart damage by dampening the production of neutrophil chemoattractants. NAMPT blockade with a neutralizing antibody has beneficial effects in an acute lung injury model. Last, but not least, the anticancer activity of NAMPT inhibitors may also reflect, at least in part, their ability to modify the cancer microenvironment through their anti-inflammatory properties. Overall, NAMPT inhibition holds potential for the treatment of inflammation-related disorders and the development of effective and safe NAMPT inhibitors remains an area of strong interest in pharmaceutical research.