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Myeloid sarcomas represent a heterogeneous group of diseases with a tumoral presentation of acute myeloid leukemia. The clinical presentation of these hematologic cancers is typically aggressive and thus rapidly fatal in the absence of treatment, which relies on intensive chemotherapy that is sometimes followed by allogeneic hematopoietic stem-cell transplant (AHSCT). However, the global treatment strategy for these lesions is currently not well established. We report the case of a patient presenting with a highly refractory mediastinal myeloid sarcoma with uncommon morphologic and phenotypic characteristics and a clonal TCR rearrangement. The patient's disease was progressive despite multiple courses of intensive chemotherapy and a combination of nelarabine and venetoclax finally led to a complete metabolic response consolidated by an AHSCT. This treatment regimen, which has never been reported before, was very well tolerated especially on the neurologic and hematologic levels. This case underlines the clinical, histologic and molecular heterogeneity of what is called myeloid sarcoma and the importance of next-generation sequencing analysis of the tumor mass with both myeloid and lymphoid panels to better classify this rare entity and identify therapeutic targets.

PURPOSE TP53-mutated ( TP53m) myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) have very poor outcome irrespective of the treatment received, including 40% responses (20% complete remission [CR]) with azacitidine (AZA) alone, short response duration, and a median overall survival (OS) of approximately 6 months. Eprenetapopt (APR-246), a novel first-in-class drug, leads to p53 protein reconformation and reactivates its proapoptotic and cell-cycle arrest functions. PATIENTS AND METHODS This phase II study assessed the safety and efficacy of eprenetapopt in combination with AZA in untreated high or very high International Prognostic Scoring System-R TP53m MDS and AML patients. RESULTS Fifty-two TP53m patients (34 MDS, 18 AML [including seven with more than 30% blasts]) were enrolled. In MDS, we observed an overall response rate (ORR) of 62%, including 47% CR, with a median duration of response at 10.4 months. In AML, the ORR was 33% including 17% CR (27% and 0% CR in AML with less than and more than 30% marrow blasts, respectively). Seventy-three percent of responders achieved TP53 next-generation sequencing negativity (ie, variant allele frequency < 5%). The main treatment-related adverse events were febrile neutropenia (36%) and neurologic adverse events (40%), the latter correlating with a lower glomerular filtration rate at treatment onset ( P < .01) and higher age ( P = .05), and resolving with temporary drug interruption without recurrence after adequate eprenetapopt dose reduction. With a median follow-up of 9.7 months, median OS was 12.1 months in MDS, and 13.9 and 3.0 months in AML with less than and more than 30% marrow blasts, respectively. CONCLUSION In this very high-risk population of TP53m MDS and AML patients, eprenetapopt combined with AZA was safe and showed potentially higher ORR and CR rate, and longer OS than reported with AZA alone.

The phosphatidylinositol 3-kinase (PI3K) pathway plays a key role in cancer progression and in host immunity. Idelalisib was the first of this class to be approved with the second-generation Pi3 kinase inhibitors copanlisib, duvelisib and umbralisib, subsequently being approved in the United States. Real-world data are lacking, however, in relation to the incidence and toxicity of Pi3 kinase inhibitor-induced colitis. We here review, in the first instance, the general landscape of the Pi3K inhibitors in the context of hematological malignancies, with a focus on the adverse gastrointestinal side effects reported by various clinical trials. We further review the available worldwide pharmacovigilance data in relation to these drugs. Finally, we describe our own real-world experience with idelalisib-induced colitis management in our center and in a national setting.

Since the development of tyrosine kinase inhibitors (TKIs) targeting BCR/ABL1 and significantly improved outcomes on long-term disease-free survival in Philadelphia chromosome–positive (Ph+) acute ...

Background Compelling evidence has emerged for the relevance of flow cytometry (FC) in the diagnostic work-up of myelodysplastic syndromes (MDS) but due to technical issues, the erythroid lineage has been under investigated, specifically in the therapeutic context. Methods Using the "no red cell lysis" method developed to set up the RED-score, we specifically quantified the fraction of CD117/c-KIT-expressing erythroid precursors in a cohort of 144 MDS patients and studied the correlation with response to erythropoiesis-stimulating agents (ESA) in a sub cohort of 63 low-risk MDS patients. Results We confirmed the previously reported increase in CD117/c-KIT-expressing erythroid precursors in a subset of MDS patients and demonstrated a strong association between a cut off of CD117/c-KIT-expressing erythroid precursors ≥3% and ESA response (P = 0.001), independent of red blood cell requirement. From our observations, we hypothesized that a decrease in CD117/c-KIT-expressing erythroid precursors could be a mechanism of ESA failure. Moreover, the fraction of CD117/c-KIT-expressing erythroid precursors was correlated with progression-free survival in low-risk MDS patients (P = 0.018). In vitro, we demonstrated in an EPO dependent cell line that CD117/c-KIT expression is necessary for cell survival under EPO stimulation. Conclusions The quantification of the CD117/c-KIT-expressing erythroid precursors could be proposed as a new theranostic and prognostic marker in MDS treated by ESA. Future studies will be required to determine whether modulating CD117/c-KIT expression and signaling could be used to improve anemia in MDS. © 2019 International Clinical Cytometry Society.

B-cell acute lymphoblastic leukemia (B-ALL) can be cured in most children and in the majority of young adults with sufficiently intensive – and myelosuppressive – combination chemotherapy regimens ...

Recent years have witnessed a dramatic improvement in multiple myeloma (MM) patient care with a current median life expectancy of 6 to 10 years dependent on age. High-dose melphalan followed by aut...

Although anti-CD38 monoclonal antibodies have improved the prognosis of relapsed/refractory multiple myeloma (RRMM), some patients still experience early relapses with poor outcomes. This present study evaluated the predictive value of FDG PET/CT parameters for RRMM prior to initiating anti-CD38 treatment. We included 38 consecutive RRMM patients who underwent a PET/CT scan treated at our institution at relapse. The median PFS was 12.5 months and the median OS was not reached. 42% of the patients had an initial ISS score of 1, 37% of 2, and 21% of 3. The presence of &gt, 3 focal lesions (FLs, n = 19) and the ISS score were associated with inferior PFS (p = 0.0036 and p = 0.0026) and OS (p = 0.025 and p = 0.0098). Patients with &gt, 3 FLs had a higher initial ISS score (p = 0.028). In multivariable analysis, the ISS score and &gt, 3 FLs were independent prognostic factors for PFS (p = 0.010 and p = 0.025 respectively), and combined they individualized a high-risk group with a median PFS and OS of 3.1 months and 8.5 months respectively vs. not reached for the other patients. The presence of &gt, 3 FLs on PET was predictive of survival outcomes in patients with RRMM treated using CD38 targeted therapy. Combined with the initial ISS, an ultra-high-risk RRMM population can thus be identified.

We would like to report a study on solitary plasmacytoma of the bone (SPB) treatment.SPB is a rare plasma cell dyscrasia characterized by a single bone tumor with no evidence of other lesions or mu...

l-asparaginase (L-ase) is a major drug used to treat acute lymphoblastic leukemia (ALL) [1]. L-ase kills leukemic cells by depleting circulating asparagine pools related to its asparaginase activit...

Sustained Leukemia-Free State and Molecular Response to Sorafenib in a Patient With Chronic Myelomonocytic Leukemia in Transformation Driven by Homozygous FLT3-ITD Malignant Hematopoiesis Olivier Kosmider, Nicolas Chapuis, Sophie Kaltenbach, Romain Coriat, Pascaline Boudou Rouquette, Lise Willems, Virginie Chesnais, Isabelle Radford-Weiss, Valerie Bardet, Patrick Mayeux, Jerome Tamburini, Michaela Fontenay, Didier Bouscary

International audience; Primary bone diffuse large B-cell lymphoma (PB-DLBCL) is a rare DLBCL location variant. We treated 76 PB-DLBCL patients by immuno-chemotherapy, resulting in an 84% sustained complete remission rate and a 78.9% survival over a 4.7-year median follow-up period. Ann Arbor stage IV and high age-adjusted international prognostic index were predictive of adverse outcome in univariate analysis. In multivariate analysis using a Cox model, only aa-IPI predicted long-term survival. While based on a limited number of cases, we suggested that radiotherapy may be useful as a consolidation modality in PB-DLBCL. We also suggested that positron emission tomography/CT scan should be interpreted with caution due to a persistent [18F]fluorodeoxyglucose [18FDG] uptake of bone lesions even after remission in some in PB-DLBCL patients. Our study based on a homogeneous cohort of PB-DLBCL patients confirmed the favorable outcome of this DLBCL variant and support the implementation of prospective clinical trials in this disease.

Myelodysplastic syndromes (MDSs) are hematopoietic stem cell disorders in which recurrent mutations define clonal hematopoiesis. The origin of the phenotypic diversity of non-del(5q) MDS remains unclear. Here, we investigated the clonal architecture of the CD34+CD38- hematopoietic stem/progenitor cell (HSPC) compartment and interrogated dominant clones for MDS-initiating cells. We found that clones mainly accumulate mutations in a linear succession with retention of a dominant subclone. The clone detected in the long-term culture-initiating cell compartment that reconstitutes short-term human hematopoiesis in xenotransplantation models is usually the dominant clone, which gives rise to the myeloid and to a lesser extent to the lymphoid lineage. The pattern of mutations may differ between common myeloid progenitors (CMPs), granulomonocytic progenitors (GMPs), and megakaryocytic-erythroid progenitors (MEPs). Rare STAG2 mutations can amplify at the level of GMPs, from which it may drive the transformation to acute myeloid leukemia. We report that major truncating BCOR gene mutation affecting HSPC and CMP was beneath the threshold of detection in GMP or MEP. Consistently, BCOR knock-down (KD) in normal CD34+ progenitors modifies their granulocytic and erythroid differentiation. Clonal architecture of the HSPC compartment and mutations selected during differentiation contribute to the phenotypic heterogeneity of MDS. Defining the hierarchy of driver mutations provides insights into the process of transformation and may guide the search for novel therapeutic strategies.

Purpose: The growth and survival of acute myeloid leukemia (AML) cells are enhanced by the deregulation of signaling pathways such as phosphoinositide 3-kinase (PI3K)/Akt and mammalian target of rapamycin (mTOR). Major efforts have thus been made to develop molecules targeting these activated pathways. The mTOR serine/threonine kinase belongs to two separate complexes: mTORC1 and mTORC2. The mTORC1 pathway is rapamycin sensitive and controls protein translation through the phosphorylation of 4E-BP1 in most models. In AML, however, the translation process is deregulated and rapamycin resistant. Furthermore, the activity of PI3K/Akt and mTOR is closely related, as mTORC2 activates the oncogenic kinase Akt. We therefore tested, in this study, the antileukemic activity of the dual PI3K/mTOR ATP-competitive inhibitor NVP-BEZ235 compound (Novartis). Experimental Design: The activity of NVP-BEZ235 was tested in primary AML samples (n = 21) and human leukemic cell lines. The different signaling pathways were analyzed by Western blotting. The cap-dependent mRNA translation was studied by 7-methyl-GTP pull-down experiments, polysomal analysis, and [3H]leucine incorporation assays. The antileukemic activity of NVP-BEZ235 was tested by analyzing its effects on leukemic progenitor clonogenicity, blast cell proliferation, and survival. Results: The NVP-BEZ235 compound was found to inhibit PI3K and mTORC1 signaling and also mTORC2 activity. Furthermore, NVP-BEZ235 fully inhibits the rapamycin-resistant phosphorylation of 4E-BP1, resulting in a marked inhibition of protein translation in AML cells. Hence, NVP-BEZ235 reduces the proliferation rate and induces an important apoptotic response in AML cells without affecting normal CD34+ survival. Conclusions: Our results clearly show the antileukemic efficiency of the NVP-BEZ235 compound, which therefore represents a promising option for future AML therapies. Clin Cancer Res; 16(22); 5424–35. ©2010 AACR.

Mammalian target of rapamycin (mTOR) is a protein kinase implicated in the regulation of various cellular processes, including those required for tumor development, such as the initiation of mRNA translation, cell-cycle progression and cellular proliferation. In a wide range of hematological malignancies, the mTORC1 signaling pathway has been found to be deregulated and has been designed as a major target for tumor therapy. Given that pre-clinical studies have clearly established the therapeutic value of mTORC1 inhibition, numerous clinical trials of rapamycin and its derivates (rapalogs) are ongoing for treatment of these diseases. At this time, although disease stabilization and tumor regression have been observed, objective responses in some tumor types have been modest. Nevertheless, some of the mechanisms underlying cancer-cell resistance to rapamycin have now been described, thereby leading to the development of new strategy to efficiently target mTOR signaling in these diseases. In this review, we discuss the rationale for using mTOR inhibitors as novel therapies for a variety of hematological, malignancies with a focus on promising new perspectives for these approaches.

Cancer cells require glutamine to adapt to increased biosynthetic activity. The limiting step in intracellular glutamine catabolism involves its conversion to glutamate by glutaminase (GA). Different GA isoforms are encoded by the genes GLS1 and GLS2 in humans. Herein, we show that glutamine levels control mitochondrial oxidative phosphorylation (OXPHOS) in acute myeloid leukemia (AML) cells. Glutaminase C (GAC) is the GA isoform that is most abundantly expressed in AML. Both knockdown of GLS1 expression and pharmacologic GLS1 inhibition by the drug CB-839 can reduce OXPHOS, leading to leukemic cell proliferation arrest and apoptosis without causing cytotoxic activity against normal human CD34(+) progenitors. Strikingly, GLS1 knockdown dramatically inhibited AML development in NSG mice. The antileukemic activity of CB-839 was abrogated by both the expression of a hyperactive GAC(K320A) allele and the addition of the tricarboxyclic acid cycle product α-ketoglutarate, indicating the critical function of GLS1 in AML cell survival. Finally, glutaminolysis inhibition activated mitochondrial apoptosis and synergistically sensitized leukemic cells to priming with the BCL-2 inhibitor ABT-199. These findings show that targeting glutamine addiction via GLS1 inhibition offers a potential novel therapeutic strategy for AML.

Cancer cells require nutrients and energy to adapt to increased biosynthetic activity, and protein synthesis inhibition downstream of mammalian target of rapamycin complex 1 (mTORC1) has shown promise as a possible therapy for acute myeloid leukemia (AML). Glutamine contributes to leucine import into cells, which controls the amino acid/Rag/mTORC1 signaling pathway. We show in our current study that glutamine removal inhibits mTORC1 and induces apoptosis in AML cells. The knockdown of the SLC1A5 high-affinity transporter for glutamine induces apoptosis and inhibits tumor formation in a mouse AML xenotransplantation model. l-asparaginase (l-ase) is an anticancer agent also harboring glutaminase activity. We show that l-ases from both Escherichia coli and Erwinia chrysanthemi profoundly inhibit mTORC1 and protein synthesis and that this inhibition correlates with their glutaminase activity levels and produces a strong apoptotic response in primary AML cells. We further show that l-ases upregulate glutamine synthase (GS) expression in leukemic cells and that a GS knockdown enhances l-ase–induced apoptosis in some AML cells. Finally, we observe a strong autophagic process upon l-ase treatment. These results suggest that l-ase anticancer activity and glutamine uptake inhibition are promising new therapeutic strategies for AML.

The serine/threonine kinase mammalian target of rapamycin (mTOR) is crucial for cell growth and proliferation, and is constitutively activated in primary acute myeloid leukemia (AML) cells, therefore representing a major target for drug development in this disease. We show here that the specific mTOR kinase inhibitor AZD8055 blocked mTORC1 and mTORC2 signaling in AML. Particularly, AZD8055 fully inhibited multisite eIF4E-binding protein 1 phosphorylation, subsequently blocking protein translation, which was in contrast to the effects of rapamycin. In addition, the mTORC1-dependent PI3K/Akt feedback activation was fully abrogated in AZD8055-treated AML cells. Significantly, AZD8055 decreased AML blast cell proliferation and cell cycle progression, reduced the clonogenic growth of leukemic progenitors and induced caspase-dependent apoptosis in leukemic cells but not in normal immature CD34+ cells. Interestingly, AZD8055 strongly induced autophagy, which may be either protective or cell death inducing, depending on concentration. Finally, AZD8055 markedly increased the survival of AML transplanted mice through a significant reduction of tumor growth, without apparent toxicity. Our current results strongly suggest that AZD8055 should be tested in AML patients in clinical trials.

The FOXO transcription factors are involved in multiple signaling pathways and have tumor-suppressor functions. In acute myeloid leukemia (AML), deregulation of oncogenic kinases, including Akt, extra-signal–regulated kinase, or IκB kinase, is frequently observed, which may potentially inactivate FOXO activity. We therefore investigated the mechanism underlying the regulation of FOXO3a, the only FOXO protein constantly expressed in AML blast cells. We show that in both primary AML samples and in a MV4-11/FOXO3a-GFP cell line, FOXO3a is in a constant inactive state due to its cytoplasmic localization, and that neither PI3K/Akt nor extra-signal–regulated kinase–specific inhibition resulted in its nuclear translocation. In contrast, the anti-Nemo peptide that specifically inhibits IKK activity was found to induce FOXO3a nuclear localization in leukemic cells. Furthermore, an IKK-insensitive FOXO3a protein mutated at S644 translocated into the nucleus and activated the transcription of the Fas-L and p21Cip1 genes. This, in turn, inhibited leukemic cell proliferation and induced apoptosis. These results thus indicate that IKK activity maintains FOXO3a in the cytoplasm and establishes an important role of FOXO3a inactivation in the proliferation and survival of AML cells. The restoration of FOXO3a activity by interacting with its subcellular distribution may thus represent a new attractive therapeutic strategy for AML.

Finding an effective treatment for acute myeloid leukemia (AML) remains a challenge, and all cellular processes that are deregulated in AML cells should be considered in the design of targeted therapies. We show in our current study that the LKB1/AMPK/TSC tumor suppressor axis is functional in AML and can be activated by the biguanide molecule metformin, resulting in a specific inhibition of mammalian target of rapamycin (mTOR) catalytic activity. This induces a multisite dephosphorylation of the key translation regulator, 4E-BP1, which markedly inhibits the initiation step of mRNA translation. Consequently, metformin reduces the recruitment of mRNA molecules encoding oncogenic proteins to the polysomes, resulting in a strong antileukemic activity against primary AML cells while sparing normal hematopoiesis ex vivo and significantly reducing the growth of AML cells in nude mice. The induction of the LKB1/AMPK tumor-suppressor pathway thus represents a promising new strategy for AML therapy.

Background Alterations in the PI3K/Akt pathway are found in a wide range of cancers and the development of PI3K inhibitors represents a promising approach to cancer therapy. Constitutive PI3K activation, reflecting an intrinsic oncogenic deregulation of primary blast cells, is detected in 50% of patients with acute myeloid leukemia. However, the mechanisms leading to this activation are currently unknown. As we previously reported IGF-1 autocriny in acute myeloid leukemia cells, we investigated whether IGF-1 signaling was involved in the constitutive activation of PI3K. Design and Methods We analyzed the IGF-1/IGF-1R signaling pathway and PI3K activity in 40 acute myeloid leukemia bone marrow samples. Specific inhibition of IGF-1/IGF-1R signaling was investigated using neutralizing anti-IGF-1R, anti-IGF-1 antibodies or IGF-1 short interfering RNA. The anti-leukemic activity of the neutralizing anti-IGF-1R was tested by analyzing its effects on leukemic progenitor clonogenicity, blast cell proliferation and survival. Results In all samples tested, we found that functional IGF-1R was constantly expressed in leukemic cells. In the acute myeloid leukemia samples with PI3K activation, we found that the IGF-1R was constitutively phosphorylated, although no IGF-1R activating mutation was detected. Specific inhibition of IGF-1R signaling with neutralizing anti-IGF-1R strongly inhibited the constitutive phosphorylation of both IGF-1R and Akt in 70% of the PI3K activated samples. Moreover, both incubation with anti-IGF-1 antibody and IGF-1 short interfering RNA inhibited Akt phosphorylation in leukemic cells. Finally, neutralizing anti-IGF-1R treatment decreased the clonogenicity of leukemic progenitors and the proliferation of PI3K activated acute myeloid leukemia cells. Conclusions Our current data indicate a critical role for IGF-1 autocriny in constitutive PI3K/Akt activation in primary acute myeloid leukemia cells and provide a strong rationale for targeting IGF-1R as a potential new therapy for this disease.

The PI3K/AKT and mTOR signaling pathways are activated in acute myeloid leukemia, including in the more immature leukemic populations. Constitutive PI3K activation is detectable in 50% of acute myeloid leukemia samples whereas mTORC1 is activated in all cases of this disease. In leukemic cells, the PI3K activity relates to the expression of the p110delta isoform of class IA PI3K. Constitutive PI3K activation is the result of autocrine IGF-1/IGF-1R signaling in 70% of acute myeloid leukemia samples but specific inhibition of this pathway does not induce apoptosis. Specific inhibition of PI3K/AKT or mTORC1 alone in vitro has anti-leukemic effects which are essentially exerted via the suppression of proliferation. However, as mTORC1 activation is independent of PI3K/AKT in acute myeloid leukemia, dual PI3K and mTOR inhibitors may induce apoptosis in blast cells. Moreover, mTORC1 inhibition using sirolimus overactivates PI3K/AKT via the upregulation of IRS2 expression and by favoring IGF-1/IGF-1R autocrine signaling. Recent data also indicate that mTORC1 does not control protein translation in acute myeloid leukemia. These results open the way for the design of direct inhibitors of protein synthesis as novel acute myeloid leukemia therapies and also for the development of second generation mTOR inhibitors (the TORKinhibs).

The deregulation of translation markedly contributes to the malignant phenotype in cancers, and the assembly of the translation initiating complex eIF4F is the limiting step of this process. The mammalian Target of Rapamycin Complex 1 (mTORC1) is thought to positively regulate eIF4F assembly and subsequent oncogenic protein synthesis through 4E-BP1 phosphorylation. We showed here that the translation inhibitor 4EGI-1 decreased the clonogenic growth of leukemic progenitors and induced apoptosis of blast cells, with limited toxicity against normal hematopoiesis, which emphasize the importance of translation deregulation in acute myeloid leukemia (AML) biology. However, the mTORC1 inhibitor RAD001 (a rapamycin derivate) did not induce AML blast cell apoptosis. We herein demonstrated that mTORC1 disruption using raptor siRNA or RAD001 failed to inhibit 4E-BP1 phosphorylation in AML. Moreover, RAD001 failed to inhibit eIF4F assembly, to decrease the proportion of polysome-bound c-Myc mRNA, and to reduce the translation-dependent accumulation of oncogenic proteins. We identified the Pim-2 serine/threonine kinase as mainly responsible for 4E-BP1 phosphorylation on the S65 residue and subsequent translation control in AML. Our results strongly implicate an mTORC1-independent deregulation of oncogenic proteins synthesis in human myeloid leukemogenesis. Direct inhibition of the translation initiating complex thus represents an attractive option for the development of new therapies in AML.

The phosphatidylinositol 3-kinase (PI3K)/Akt and mammalian target of rapamycin complex 1 (mTORC1) signaling pathways are frequently activated in acute myelogenous leukemia (AML). mTORC1 inhibition with RAD001 induces PI3K/Akt activation and both pathways are activated independently, providing a rationale for dual inhibition of both pathways. PI-103 is a new potent PI3K/Akt and mTOR inhibitor. In human leukemic cell lines and in primary blast cells from AML patients, PI-103 inhibited constitutive and growth factor-induced PI3K/Akt and mTORC1 activation. PI-103 was essentially cytostatic for cell lines and induced cell cycle arrest in the G1 phase. In blast cells, PI-103 inhibited leukemic proliferation, the clonogenicity of leukemic progenitors and induced mitochondrial apoptosis, especially in the compartment containing leukemic stem cells. In contrast, apoptosis was not induced with RAD001 and IC87114 association, which specifically inhibits mTORC1 and p110delta activity, respectively. PI-103 had additive proapoptotic effects with etoposide in blast cells and in immature leukemic cells. Interestingly, PI-103 did not induce apoptosis in normal CD34(+) cells and had moderate effects on their clonogenic and proliferative properties. Here, we demonstrate that multitargeted therapy against PI3K/Akt and mTOR with PI-103 may be of therapeutic value in AML.

The phosphatidylinositol 3-kinase (PI3K)/Akt and mTORC1 pathways are frequently activated, representing potential therapeutic targets in acute myeloid leukemia (AML). In 19 AML samples with constitutive PI3K/Akt activation, the rapamycin derivative inhibitor everolimus (RAD001) increased Akt phosphorylation. This mTOR C1-mediated Akt up-regulation was explained by an insulin-like growth factor-1 (IGF-1)/IGF-1 receptor autocrine loop: (1) blast cells expressed functional IGF-1 receptors, and IGF-1-induced Akt activation was increased by RAD001, (2) a neutralizing anti-IGF-1R α-IR3 monoclonal antibody reversed the RAD001-induced Akt phosphorylation, and (3) autocrine production of IGF-1 was detected in purified blast cells by quantitative reverse transcription-polymerase chain reaction and immunofluorescence. This RAD001-induced PI3K/Akt up-regulation was due to an up-regulated expression of the IRS2 adaptor. Finally, we observed that concomitant inhibition of mTORC1 and PI3K/Akt by RAD001 and IC87114 induced additive antiproliferative effects. Our results suggest that dual inhibition of the mTORC1 complex and the IGF-1/IGF-1R/PI3K/Akt pathway in AML may enhance the efficacy of mTOR inhibitors in treatment of this disease.

Abstract 4786 Background Chronic myelomonocytic leukemia (CMML) is a rare clonal hematopoietic stem cell disorder whom biology remains unclear.CMML is associated with many different somatic mutations in genes involved in key cellular processes including signaling (N/K-Ras, CBL, JAK2); differentiation (RUNX1, NPM1, CEBPa); epigenetic regulation (TET2, ASXL1, IDH1/2, EZH2, DNMT3A); and RNA splicing (SRSF2, U2AF1, SF3B1 and ZRSR2). FLT3 mutations are very rare but provide the rationale for FLT3 tyrosine kinase inhibitor use to treat this disease. We report the case of a 60-years-old patient diagnosed with a hepatocarcinoma metastasis which legitimized the introduction of anti-angiogenic therapy using the VEGF-R2 inhibitor, sorafenib. The patient was addressed to the hematology department with a myeloproliferative-like CMML in transformation. We show here that the molecular analyses of this hematological disorders allow us to use sorafenib as a targeted therapy to inhibit the consequences of a FLT3-ITD mutation. Methods Cytogenetic analysis and genome wide array-based comparative genomic hybridization (aCGH) were performed at diagnosis. The reference standard used for aCGH was matched genomic constitutional DNA (CD3+ T cells sorted from a blood sample). Serum samples collected from the patient before or under treatment with sorafenib were assessed for their plasma inhibitory activity by western blotting analyses of signaling molecules downstream the FLT3-ITD mutation. Genomic DNA samples extracted from BMMCs and peripheral blood (PB) cells at diagnosis were screened for mutations in 18 classical genes. To monitor the FLT3-ITD mutation, the exon 15 of FLT3 was amplified by a specific PCR using a 6FAM-labeled forward primer. Results The patient developed hyperleucocytosis (48.2 G/L) with neutrophilia (30.4 G/L), monocytosis (11.6 G/L) and basophilia (0.5 G/L) in January 2011. The BM was hypercellular with granulocytic and monocytic proliferation, dysgranulopoiesis and dysmegacaryopoiesis. Blast cells plus promonocytes accounted for 30% of the nucleated BM cells, leading to a diagnosis of AML secondary to CMML in the WHO classification BM karyotype identified no clonal abnormalities and aCGH analysis of BMMCs produced normal findings. BM and PB cells were screened for mutations in 18 CMML-associated genes. Only two abnormalities were identified: a 27 base pair (bp) insertion FLT3-ITD mutation (exon 15) detected in BM cells with near complete disappearance of the wild type (WT) FLT3 allele (FLT3-ITD/FLT3-WT ratio at 9.62) and a classical heterozygous mutation (dupG) was found in the exon 12 of ASXL1. ASXL1 and FLT3-ITD mutations were not detected in purified CD3+ T lymphocytes. Five months after sorafenib introduction, PB was strictly normal and BM examination demonstrated normal richness, blast cells and promonocytes accounting for 2% of the nucleated BM cells but persistent moderate dysgranulopoiesis and dysmegakaryopoiesis, indicative of complete remission. At this time, the FLT3-ITD/FLT3-WT ratio was 1.66 and 0.58 in the BM and PB, respectively. In January 2012, the WBC profile was still normal and a BM smear only showed moderate dysgranulopoiesis. On the molecular side, FLT3-ITD mutation was undetectable, indicative of complete molecular response. But ASXL1 mutation was evident at all time points. The serum of the patient, obtained before and under sorafenib was tested on cell line harboring FLT3-ITD mutation. Constitutive FLT3 Y591, Akt S473, STAT5 Y694 and ERK1/2 T202/Y204 phosphorylations were fully inhibited in the presence of the serum extracted under sorafenib treatment. Conclusion Our patient clearly had a myeloproliferative-CMML driven by an homozygous FLT3-ITD mutation. This is the first report of such a CMML patient achieving sustained CR and CMR after treatment with an FLT3-ITD tyrosine kinase inhibitor. In this case, the ASXL1 mutation remained detectable upon sorafenib treatment after the suppression of FLT3-ITD-driven malignant hematopoiesis, suggesting that it arose from a FLT3-WT subclone that contributed to the CMML phenotype with some dysplastic feature. In conclusion, we propose that mutations in the FLT3 gene should be examinated in all CMML cases, even their low frequency because FLT3 TKI may induce dramatic and sustained responses without significant toxicity and eventually allow for allogenic transplantation. Disclosures: No relevant conflicts of interest to declare.

Abstract 1024 Poster Board I-46 The treatment of acute myeloid leukemia (AML) still represents a challenge. As the growth and survival of AML cells are enhanced by the deregulation of signaling pathways such as PI3K, ERK/MAPK or mTOR, major efforts are made to develop targeted molecules against these activated pathways. The mTOR serine/threonine kinase belongs to two separate complexes, mTORC1 and mTORC2. The mTORC1 complex, defined by the interaction between mTOR and raptor, is inhibited by rapamycin in most models. It controls mRNA translation through the phosphorylation of the physiological translation repressor 4E-BP1. A constitutive activation of mTORC1 is usually detected in primary AML cells, indicating this pathway as a major target for AML therapy. However, inhibition of mTORC1 with rapamycin has only modest effects in this disease (Recher, Beyne-Rauzy et al., Blood 2005; Xu, Thompson et al.,Blood 2005). Accordingly, we recently showed that the translation process is deregulated and rapamycin resistant in AML, although specifically targeting translation with the 4E-BP1 mimetic 4EGI-1 markedly impairs AML cells survival (Tamburini, Green et al., Blood 2009). The mTORC2 complex is defined by the interaction between rictor and mTOR and is generally reported as resistant to rapamycin. An emerging role for mTORC2 has recently been rose in cancer biology, including in AML, in part through its ability to activate the oncogenic kinase Akt by phosphorylation on S473 (Zeng, Sarbassov dos et al., Blood 2007). In AML, the PI3K and mTOR activities are closely connected: inhibition of mTORC1 activates an IGF-1/IGF-1R autocrine loop that overactivates PI3K but mTORC1 activity is PI3K-independent (Tamburini, Chapuis et al., Blood 2008). These results strongly suggest a rational for simultaneous inhibition of PI3K and mTOR to enhance the killing of AML cells (Park, Chapuis et al., Leukemia 2008; Tamburini, Chapuis et al., Blood 2008). The NVP-BEZ235 compound (Novartis®) is an ATP-competitive inhibitor specific of PI3K and mTOR kinases, actually in phase I/II trial in oncology. We tested for the first time NVP-BEZ235 in 3 human AML cell lines (MV4-11, MOLM-14 and OCI-AML3) and in primary AML samples (n=10). This compound inhibited PI3K and mTOR signaling without off-target effects against other kinases usually activated in AML cells (ERK1/2 and STAT5). In contrast to rapamycin, NVP-BEZ235 dose-dependently inhibited the catalytic activity of mTOR as attested by inhibition of the mTOR autophosphorylation site on S2481. Consequently, NVP-BEZ235 fully inhibited the rapamycin-resistant phosphorylation of the translation repressor 4E-BP1 on T37/46, T70 and S65 residues. This resulted in a marked inhibition of mRNA translation in AML cells, attested by (i) an inhibition of the assembly of the translation initiating complex eIF4F, (ii) a shift from large to small polysomes in NVP-BEZ235-treated AML cells and (iii) a decreased expression of the oncogenic cap-dependant proteins Bcl-XL, c-myc and cyclinD1. Moreover, to study the effects of NVP-BEZ235 on mTORC2 activity independently of Akt, we investigated the regulation of the mTORC2 substrate paxillin (Jacinto, Loewith et al., Nat Cell biol 2004). We first confirmed that paxillin Y118 residue was a substrate for mTORC2 activity in primary AML cells as the siRNA-mediated rictor knockdown dramatically inhibited this phosphorylation event. In primary AML samples, NVP-BEZ235 inhibited paxillin Y118 phosphorylation in a dose-dependent way and this closely correlated to the inhibition of Akt S473 phosphorylation. Targeting the catalytic activity of mTOR represses therefore both mTORC1 and mTORC2 activity. Accordingly, the NVP-BEZ235 compound had marked anti-leukemic activity in AML. Indeed, it strongly reduced the proliferation of AML cells and blocked the cell-cycle as attested by a decrease of AML cells in S-phase and an accumulation in G1-phase. Finally, NVP-BEZ235 induced an important apoptotic response in AML blast cells but its effects on normal hematopoiesis were limited ex vivo. Overall, NVP-BEZ235 strongly inhibited protein synthesis and induced the killing of AML cells through the catalytic inhibition of the oncogenic PI3K and mTOR kinases. Given these results, NVP-BEZ235 may be tested urgently in clinical trials in AML. Disclosures: No relevant conflicts of interest to declare.

In most cancer models, the PI3K/Akt pathway controls the activity of the mammalian Target of Rapamycin Complex 1 (mTORC1) that regulates cell growth through the phosphorylation of P70S6K and 4E-BP1. In Acute Myeloid Leukemia (AML), both constitutive activation of PI3K (PI3K+) and of mTORC1 are detected. We previously reported in AML that PI3K activity is due to the expression of the p110d isoform of class Ia PI3K and is constitutive in 50% of samples at diagnosis. We show here in primary AML samples that the constitutive activity of mTORC1, detected by the phosphorylation of P70S6K on Thr389, is not due to PI3K/Akt activation. In PI3K+ samples, the specific inhibition of p110d with IC87114 does not inhibit mTORC1. Furthermore, a constitutive activity of mTORC1 is detected in almost all AML samples regardless of their PI3K/ Akt activation status. Similarly, the inhibition of ERK/MAPK activity with UO126 does not result in mTORC1 inhibition. Interestingly, in primary AML cells, we shows that mTORC1 is fully inhibited following leucine starvation as observed in non-transformed cells, suggesting that the kinase activity of mTOR is not deregulated and remains accessible to target inhibition. We thus focused on the links between the AMP kinase (AMPK) and mTORC1. AMPK is a physiological cellular energy sensor and becomes phosphorylated at Thr172 downstream of LKB1 in response to a decrease in cellular ATP levels. AMPK then controls multiple metabolic processes such as fatty acid oxidation, glucose production and protein synthesis. Interestingly, AMPK is usually unphosphorylated in cancer cells including AML and thereby represents a potential therapeutic target. We thus investigated the effects of metformin, a potent AMPK activator developed as an oral anti-diabetic drug, in primary AML cells. This compound induces a dose-dependent activation of AMPK that correlates with a decrease of mTORC1 activity. Primary AML blast cells cultured with metformin show a significant inhibition of proliferation, of clonogenic growth and apoptosis suggesting that AMPK may be an attractive anticancer therapeutic target in AML. However, as metformin may exerts AMPK-independent effects, we are producing a lentiviral construct expressing a constitutively activated AMPK mutant to more specifically determine the consequences of AMPK activation in mTORC1 signaling and blast cells survival.

Background: The PI3K/AKT signaling pathway is frequently activated in blast cells from AML patients, and also detected in the leukemic stem cell (LSCs). The p110δ catalytic subunit of class IA PI3K is constantly expressed in leukemic cells, and IC87114, a specific p110δ inhibitor, inhibits Akt phosphorylation, reduces blast cell proliferation, but does not induce apoptosis in AML cells. The mTORC1 pathway is also activated in 50 to 70% of AML samples. Rapamycin and its derivative RAD001, inhibit mTORC1 activity, decrease the clonogenicity of leukemic progenitors, but induce low rates of apoptosis. LY294002 inhibits all p110 isoforms of PI3K as well as most kinases of the PIKK family but can not be used in clinical practice because of its toxicity. Pharmaceutical industry effort identified more selective PI3K inhibitors, and among them, PI-103, a small synthetic molecule of the pyridofuropyrimidine class, is potentially interesting as a selective PI3K inhibitor and also as an mTOR inhibitor. Materials and methods: Bone marrow (BM) samples were obtained from 20 newly diagnosed patients with de novo AML, treated in the AML2001 trial of chemotherapy, initiated by the GOELAMS. The MOLM-14 and OCI-AML-3 leukemic cell lines were obtained from ATCC. CD34+ cells from 5 normal allogeneic donors were purified after cytapheresis. Results: We studied the effect of PI-103 in MOLM-14 and OCI-AML-3. We observed a dose-dependent inhibition of AKT (Ser 473 and Thr 308), FOXO3a (Thr 32), and p70S6-kinase (Thr 389) phosphorylation with 0.1, 1 or 5 μM PI-103. 1μM PI-103 was as effective as 25 μM LY294002 or 10 nM RAD001 at inhibiting PI3K/AKT or mTORC1 activity, respectively. 1μM PI-103 dramatically inhibited the proliferation of both cell lines. However, PI-103 was essentially cytostatic and did not induce significant apoptosis in these cells. For subsequent experiments on primary AML blasts, the dose of 1 μM PI-103 was chosen as it was sufficient to inhibit AKT and p70S6K phosphorylations. The effect of 1μM PI-103 on PI3K/AKT and mTORC1 activation was evaluated in 5 AML samples (3 with constitutive PI3K activation (PI3K+) and 2 without constitutive PI3K activation (PI3K-)). 1 μM PI-103 inhibited completely basal and SCF or Flt3-L-stimulated AKT, FOXO3A phosphorylation and P70S6K phosphorylation in these AML samples. PI-103 dramatically inhibited both basal and growth factor-stimulated proliferation of blast cells. Interestingly, PI-103 induced significant apoptosis in 6 AML samples at 1μM and a significant decrease of CFU-L colonies in 6 other AML samples. In contrast, specific inhibition of the catalytic activity of the p110δ isoform and of the mTORC1 complex, with IC87114 and RAD001 respectively, did not induce apoptosis. Finally, excess of apoptosis was also obtained in the CD34+ CD38Low/Neg CD123+ LSCs from 4 patients in presence of PI-103 alone. Moreover, the functional effects of PI-103 on normal CD34+ cells were low, indicating that this compound may have a favourable therapeutic index. Conclusions: Our results suggest that multi-targeted therapy toward PI3K/AKT and mTOR may be efficient in AML and particularly useful to target LSCs.

The deregulation of translation, leading to a preferential translation of oncogene-related mRNAs, markedly contributes to the malignant phenotype in human cancers. The assembly of the eukaryotic translation Initiation Factor 4F (eIF4F) complex is limiting for malignancy-related translation events and is hence an attractive anticancer therapeutic target. The Mammalian Target Of Rapamycin Complex 1 (mTORC1) is thought to positively regulate eIF4F assembly and subsequent oncogenic protein synthesis through eIF4E Binding Protein 1 (4E-BP1) phosphorylation. The mTORC1 inhibitor rapamycin has been developed as an anti-cancer agent but is of limited efficacy in the treatment of Acute Myeloid Leukemia (AML). We show in our study that in primary AML cells, 4E-BP1 phosphorylation is mTORC1-independent and is in fact controlled by the Pim- 2 serine/threonine kinase: neither the rapamycin derivate RAD001 nor Raptor siRNA inhibited 4E-BP1 phosphorylation contrary to siRNA-mediated Pim-2 knock-down. We utilized the 4E-BP1 mimetic 4EGI-1, as a direct inhibitor of translation in AML. In contrast to RAD001, 4EGI-1 totally inhibited eIF4F assembly; markedly decreased the proportion of polysome-bound c-Myc mRNA; and dramatically decreased the accumulation of oncogenic proteins that are regulated at the translational level. Moreover, 4EGI-1 demonstrated potent anti-leukemic activity ex vivo in primary AML blast cells through a selective suppression of proteins implicated in proliferation and in anti-apoptotic mechanisms. Significantly, these effects occurred with a minimal degree of toxicity against normal hematopoietic processes. Our present results therefore strongly implicate an mTORC1-independent mechanism of deregulated synthesis of oncogenic proteins in human myeloid leukemogenesis. The direct inhibition of the eIF4F translation initiating complex, by 4EGI-1, by the recently developed eIF4E antisense oligonucleotides or by specific Pim-2 inhibitors when available, thus represents an attractive option for the development of new therapies for AML.

The PI3K/Akt axis is implicated in cell proliferation and survival and appears promising for target inhibition. The constitutive activation of PI3K (PI3K+) that reflects intrinsic cytokine-independent signaling properties of blast cells is detected in 50% of AML samples at diagnosis. Several cytokines and growth factors are known to stimulate the PI3K/Akt pathway, such as FLT-3, SCF or IGF-1 but the mechanisms leading to the constitutive PI3K activation are unknown. The IGF-1/IGF-1R signaling is thought to have a crucial role in the development and progression of cancers. In AML, IGF-1 promotes cell growth and survival via PI3K signaling. As we previously reported an IGF-1 autocrine production in AML leukemic cells, we investigated whether IGF-1/IGF-1R signaling could be responsible for the constitutive activity of PI3K in AML. We show here in primary AML blast cells that IGF-1R is constantly expressed and constitutively phosphorylated in PI3K+ samples. The constitutive phosphorylation of Akt is fully inhibited in 70% of PI3K+ samples by aIR3, a neutralizing anti-IGF-1R monoclonal antibody but neither ERK nor P70S6K phosphorylation are modified by aIR3. Moreover, siRNA-mediated decrease of the IGF-1 autocrine production markedly reduces Akt phosphorylation in leukemic cells. Finally, no mutation is detected within the complete sequence of IGF-1R cDNA from PI3K+ AML samples. In conclusion, the constitutive activity of PI3K/Akt proceed from the activation of IGF-1R due to an IGF-1 autocriny in 70% of PI3K+ primary AML samples. Our current data strengthen the rational of targeted therapy against IGF-1R in AML.