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Pentraxin-related protein 3 (PTX3), commonly produced by myeloid and endothelial cells, is a humoral pattern recognition protein of the innate immune system. Because PTX3 plasma levels of patients with chronic lymphocytic leukemia (CLL) are high and most circulating cells in patients with CLL are CLL cells, we reasoned that CLL cells produce PTX3. Western immunoblotting revealed that low-density cells from seven of seven patients with CLL produce high levels of PTX3, flow cytometry analysis revealed that the PTX3-producing cells are B lymphocytes coexpressing CD19 and CD5, and confocal microscopy showed that PTX3 is present in the cytoplasm of CLL cells. Because STAT3 is constitutively activated in CLL cells, and because we identified putative STAT3 binding sites within the PTX3 gene promoter, we postulated that phosphorylated STAT3 triggers transcriptional activation of PTX3. Immunoprecipitation analysis of CLL cells’ chromatin fragments showed that STAT3 Abs precipitated PTX3 DNA. STAT3 knockdown induced a marked reduction in PTX3 expression, indicating a STAT3-induced transcriptional activation of the PTX3 gene in CLL cells. Using an EMSA, we established and used a dual-reporter luciferase assay to confirm that STAT3 binds the PTX3 gene promoter. Downregulation of PTX3 enhanced apoptosis of CLL cells, suggesting that inhibition of PTX3 might benefit patients with CLL.

PDF File - 310K, Treatment with BEZ235 dose dependently inhibits PI3K/AKT and mTOR signaling in MPN cells.

Legends for Supplementary Figures 1-5.

Hemopoietic progenitor cells (HPC) from myeloproliferative neoplasms (MPN) such as myelofibrosis commonly express mutant JAK2-V617F or other mutations that are associated with increased activities of JAK-STAT5/3, RAS/RAF/MAPK, and PI3K/AKT/mTOR pathways. This confers proliferative and survival advantage on the MPN HPCs. Treatment with JAK tyrosine kinase inhibitor (TKI), for example, TG101209, TG101348 (SAR302503), or INCB018424 (ruxolitinib), inhibits mutant JAK2-mediated signaling. Although effective in reducing constitutional symptoms and splenomegaly, treatment with JAK-TKI does not ameliorate myelofibrosis or significantly improve survival of patients with advanced myelofibrosis. Here, we show that treatment with the dual phosphoinositide-3-kinase (PI3K)/AKT and mTOR inhibitor BEZ235 attenuated PI3K/AKT and mTOR signaling, as well as induced cell-cycle growth arrest and apoptosis of the cultured human JAK2-V617F-expressing HEL92.1.7 (HEL), UKE1 cells, and primary CD34+ myelofibrosis (MF)-MPN cells. Treatment with BEZ235 also induced significant apoptosis of the JAK2-TKI resistant HEL/TGR cells that were selected for resistance against JAK-TKI. Cotreatment with BEZ235 and JAK2-TKI (TG101209 and SAR302503) synergistically induced lethal activity against the cultured and primary CD34+ MPN cells while relatively sparing the normal CD34+ HPCs. These findings create a compelling rationale to determine the in vivo activity of dual PI3K/mTOR inhibitors in combination with JAK inhibitors against myelofibrosis HPCs. Mol Cancer Ther; 12(5); 577–88. ©2013 AACR.

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Supplementary Tables 1-3 from Genetic Analysis of Transforming Events That Convert Chronic Myeloproliferative Neoplasms to Leukemias

Supplementary Figures 1-4 from Bone Marrow Stroma–Secreted Cytokines Protect JAK2V617F-Mutated Cells from the Effects of a JAK2 Inhibitor

The oncogenetic events that transform chronic myeloproliferative neoplasms (MPN) to acute myeloid leukemias (AML) are not well characterized. We investigated the role of several genes implicated in leukemic transformation by mutational analysis of 63 patients with AML secondary to a preexisting MPN (sAML). Frequent mutations were identified in TET2 (26.3%), ASXL1 (19.3%), IDH1 (9.5%), and JAK2 (36.8%) mutations in sAML, and all possible mutational combinations of these genes were also observed. Analysis of 14 patients for which paired samples from MPN and sAML were available showed that TET2 mutations were frequently acquired at leukemic transformation [6 of 14 (43%)]. In contrast, ASXL1 mutations were almost always detected in both the MPN and AML clones from individual patients. One case was also observed where TET2 and ASXL1 mutations were found before the patient acquired a JAK2 mutation or developed clinical evidence of MPN. We conclude that mutations in TET2, ASXL1, and IDH1 are common in sAML derived from a preexisting MPN. Although TET2/ASXL1 mutations may precede acquisition of JAK2 mutations by the MPN clone, mutations in TET2, but not ASXL1, are commonly acquired at the time of leukemic transformation. Our findings argue that the mutational order of events in MPN and sAML varies in different patients, and that TET2 and ASXL1 mutations have distinct roles in MPN pathogenesis and leukemic transformation. Given the presence of sAML that have no preexisting JAK2/TET2/ASXL1/IDH1 mutations, our work indicates the existence of other mutations yet to be identified that are necessary for leukemic transformation. Cancer Res; 70(2); 447–52

Supplementary Figure Legends 1-4 from Bone Marrow Stroma–Secreted Cytokines Protect JAK2V617F-Mutated Cells from the Effects of a JAK2 Inhibitor

Signals emanating from the bone marrow microenvironment, such as stromal cells, are thought to support the survival and proliferation of the malignant cells in patients with myeloproliferative neoplasms (MPN). To examine this hypothesis, we established a coculture platform [cells cocultured directly (cell-on-cell) or indirectly (separated by micropore membrane)] designed to interrogate the interplay between Janus activated kinase 2-V617F (JAK2V617F)–positive cells and the stromal cells. Treatment with atiprimod, a potent JAK2 inhibitor, caused marked growth inhibition and apoptosis of human (SET-2) and mouse (FDCP-EpoR) JAK2V617F-positive cells as well as primary blood or bone marrow mononuclear cells from patients with polycythemia vera; however, these effects were attenuated when any of these cell types were cocultured (cell-on-cell) with human marrow stromal cell lines (e.g., HS5, NK.tert, TM-R1). Coculture with stromal cells hampered the ability of atiprimod to inhibit phosphorylation of JAK2 and the downstream STAT3 and STAT5 pathways. This protective effect was maintained in noncontact coculture assays (JAK2V617F-positive cells separated by 0.4-μm-thick micropore membranes from stromal cells), indicating a paracrine effect. Cytokine profiling of supernatants from noncontact coculture assays detected distinctly high levels of interleukin 6 (IL-6), fibroblast growth factor (FGF), and chemokine C-X-C-motif ligand 10 (CXCL-10)/IFN-γ–inducible 10-kD protein (IP-10). Anti-IL-6, -FGF, or -CXCL-10/IP-10 neutralizing antibodies ablated the protective effect of stromal cells and restored atiprimod-induced apoptosis of JAK2V617F-positive cells. Therefore, our results indicate that humoral factors secreted by stromal cells protect MPN clones from JAK2 inhibitor therapy, thus underscoring the importance of targeting the marrow niche in MPN for therapeutic purposes. Cancer Res; 71(11); 3831–40. ©2011 AACR.

Phenotypic characterization of T cells in myelofibrosis is intriguing because of increased inflammation, markedly elevated pro-inflammatory cytokines, and altered distribution of T-cell subsets. Constitutive activation of Janus kinase-2 (JAK2) in the majority of patients with myelofibrosis contributes to the expression of the programmed cell death protein-1 (PD1) and T-cell exhaustion. We wondered whether T-cell activation affects treatment outcome of patients with myelofibrosis and sought to determine whether the JAK1/2 inhibitor ruxolitinib affects the activation of T-cell subsets. T cells from 47 myelofibrosis patients were analyzed and the percentages of either helper (CD4+) or cytotoxic (CD8+) naïve, central memory, effector memory, or effector T cells; and fractions of PD1-expressing cells in each subset were assessed. Higher numbers of T cells co-expressing CD4/PD1 and CD8/PD1 were found in myelofibrosis patients than in healthy controls (n=28), and the T cells were significantly skewed toward an effector phenotype in both CD4+ and CD8+ subsets, consistent with a shift from a quiescent to an activated state. Over the course of ruxolitinib treatment, the distribution of aberrant T-cell subsets significantly reversed towards resting cell phenotypes. CD4+ and CD8+ subsets at baseline correlated with monocyte and platelet counts, and their PD1+ fractions correlated with leukocyte counts and spleen size. Low numbers of PD1+/CD4+ and PD1+/CD8+ cells were associated with complete resolution of palpable splenomegaly and improved survival rate, suggesting that low levels of exhausted T cells confer a favorable response to ruxolitinib treatment.

The promising activity of BET protein inhibitors (BETi’s) is compromised by adaptive or innate resistance in acute myeloid leukemia (AML). Here, modeling of BETi-persister/resistance (BETi-P/R) in human postmyeloproliferative neoplasm (post-MPN) secondary AML (sAML) cells demonstrated accessible and active chromatin in specific superenhancers/enhancers, which was associated with increased levels of nuclear β-catenin, TCF7L2, JMJD6, and c-Myc in BETi-P/R sAML cells. Following BETi treatment, c-Myc levels were rapidly restored in BETi-P/R sAML cells. CRISPR/Cas9-mediated knockout of TCF7L2 or JMJD6 reversed BETi-P/R, whereas ectopic overexpression conferred BETi-P/R in sAML cells, confirming the mechanistic role of the β-catenin–TCF7L2–JMJD6–c-Myc axis in BETi resistance. Patient-derived, post-MPN, CD34+ sAML blasts exhibiting relative resistance to BETi, as compared with sensitive sAML blasts, displayed higher messenger RNA and protein expression of TCF7L2, JMJD6, and c-Myc and following BETi washout exhibited rapid restoration of c-Myc and JMJD6. CRISPR/Cas9 knockout of TCF7L2 and JMJD6 depleted their levels, inducing loss of viability of the sAML blasts. Disruption of colocalization of nuclear β-catenin with TBL1 and TCF7L2 by the small-molecule inhibitor BC2059 combined with depletion of BRD4 by BET proteolysis-targeting chimera reduced c-Myc levels and exerted synergistic lethality in BETi-P/R sAML cells. This combination also reduced leukemia burden and improved survival of mice engrafted with BETi-P/R sAML cells or patient-derived AML blasts innately resistant to BETi. Therefore, multitargeted disruption of the β-catenin–TCF7L2–JMJD6–c-Myc axis overcomes adaptive and innate BETi resistance, exhibiting preclinical efficacy against human post-MPN sAML cells.

Bone marrow (BM) sclerosis is commonly found in patients with late-stage myelofibrosis (MF). Because osteoclasts (OCs) and osteoblasts play a key role in bone remodeling, and MF monocytes, the OC precursors, are derived from the neoplastic clone, we wondered whether decreased OC numbers or impairment in their osteolytic function affects the development of osteosclerosis. Analysis of BM biopsies from 50 MF patients showed increased numbers of multinucleated tartrate-resistant acid phosphatase (TRAP)/cathepsin K+ OCs expressing phosphorylated Janus kinase 2 (JAK2). Randomly microdissected TRAP+ OCs from 16 MF patients harbored JAK2 or calreticulin (CALR) mutations, confirming MF OCs are clonal. To study OC function, CD14+ monocytes from MF patients and healthy individuals were cultured and differentiated into OCs. Unlike normal OCs, MF OCs appeared small and round, with few protrusions, and carried the mutations and chromosomal abnormalities of neoplastic clones. In addition, MF OCs lacked F-actin–rich ring-like structures and had fewer nuclei and reduced colocalization signals, compatible with decreased fusion events, and their mineral resorption capacity was significantly reduced, indicating impaired osteolytic function. Taken together, our data suggest that, although the numbers of MF OCs are increased, their impaired osteolytic activity distorts bone remodeling and contributes to the induction of osteosclerosis.

There is an unmet need to overcome nongenetic therapy-resistance to improve outcomes in AML, especially post-myeloproliferative neoplasm (MPN) secondary (s) AML. Studies presented describe effects of genetic knockout, degradation or small molecule targeted-inhibition of GFI1/LSD1 on active enhancers, altering gene-expressions and inducing differentiation and lethality in AML and (MPN) sAML cells. A protein domain-focused CRISPR screen in LSD1 (KDM1A) inhibitor (i) treated AML cells, identified BRD4, MOZ, HDAC3 and DOT1L among the codependencies. Our findings demonstrate that co-targeting LSD1 and one of these co-dependencies exerted synergistic in vitro lethality in AML and post-MPN sAML cells. Co-treatment with LSD1i and the JAKi ruxolitinib was also synergistically lethal against post-MPN sAML cells. LSD1i pre-treatment induced GFI1, PU.1 and CEBPα but depleted c-Myc, overcoming nongenetic resistance to ruxolitinib, or to BETi in post-MPN sAML cells. Co-treatment with LSD1i and BETi or ruxolitinib exerted superior in vivo efficacy against post-MPN sAML cells. These findings highlight LSD1i-based combinations that merit testing for clinical efficacy, especially to overcome nongenetic therapy-resistance in AML and post-MPN sAML.

The glioma associated oncogene-1 (GLI1), a downstream effector of the embryonic Hedgehog pathway, was detected in chronic lymphocytic leukemia (CLL), but not normal adult cells. GLI1-activating mutations were identified in 10% of patients with CLL. However, what induces GLI1 expression in GLI1-unmutated CLL cells is unknown. Because signal transducer and activator of transcription 3 (STAT3) is constitutively activated in CLL cells, and sequence analysis detected putative STAT3-binding sites in the GLI1 gene promoter, we hypothesized that STAT3 induces the expression of GLI1. Western immunoblotting detected GLI1 in CLL cells from 7 of 7 patients, flow cytometry analysis confirmed that CD19+/CD5+ CLL cells co-express GLI1, and confocal microscopy showed co-localization of GLI1 and phosphorylated STAT3. Chromatin immunoprecipitation showed that STAT3 protein co-immunoprecipitated GLI1, as well as other STAT3-regulated genes. Transfection of CLL cells with STAT3-shRNA induced a mark decrease in GLI1 levels, suggesting that STAT3 binds to and induces the expression of GLI1 in CLL cells. An electromobility shift assay confirmed that STAT3 binds, and a luciferase assay showed that STAT3 activates the GLI1 gene. Transfection with GLI1-siRNA significantly increased the spontaneous apoptosis rate of CLL cells, suggesting that GLI1 inhibitors might provide therapeutic benefit to patients with CLL.

The glioma associated oncogene-1 (GLI1), a downstream effector of the embryonic Hedgehog pathway, was detected in chronic lymphocytic leukemia (CLL), but not normal adult cells. GLI1 activating mutations were identified in 10% of patients with CLL. However, what induces GLI1 expression in GLI1-unmutated CLL cells is unknown. Because signal transducer and activator of transcription 3 (STAT3) is constitutively activated in CLL cells and sequence analysis detected putative STAT3-binding sites in the GLI1 gene promoter, we hypothesized that STAT3 induces the expression of GLI1. Western immunoblotting detected GLI1 in CLL cells from 7 of 7 patients, flow cytometry analysis confirmed that CD19+/CD5+ CLL cells co-express GLI1 and confocal microscopy showed co-localization of GLI1 and phosphorylated STAT3. Chromatin immunoprecipitation showed that STAT3 protein co-immunoprecipitated GLI1 as well as other STAT3-regulated genes. Transfection of CLL cells with STAT3-shRNA induced a mark decrease in GLI1 levels, suggesting that STAT3 binds to and induces the expression of GLI1 in CLL cells. An electromobility shift assay confirmed that STAT3 binds, and a luciferase assay showed that STAT3 activates the GLI1 gene. Transfection with GLI1-siRNA significantly increased the spontaneous apoptosis rate of CLL cells, suggesting that GLI1 inhibitors might provide therapeutic benefit to patients with CLL.

Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by cytopenia and extramedullary hematopoiesis, resulting in splenomegaly. Multiple pathological mechanisms (e.g., circulating cytokines and genetic alterations, such as JAKV617F mutation) have been implicated in the etiology of MF, but the molecular mechanism causing resistance to JAK2V617F inhibitor therapy remains unknown. Among MF patients who were treated with the JAK inhibitor ruxolitinib, we compared noncoding RNA profiles of ruxolitinib therapy responders versus nonresponders and found miR-543 was significantly upregulated in nonresponders. We validated these findings by reverse transcription–quantitative PCR. in this same cohort, in 2 additional independent MF patient cohorts from the United States and Romania, and in a JAK2V617F mouse model of MF. Both in vitro and in vivo models were used to determine the underlying molecular mechanism of miR-543 in MF. Here, we demonstrate that miR-543 targets the dioxygenases ten-eleven translocation 1 (TET1) and 2 (TET2) in patients and in vitro, causing increased levels of global 5-methylcytosine, while decreasing the acetylation of histone 3, STAT3, and tumor protein p53. Mechanistically, we found that activation of STAT3 by JAKs epigenetically controls miR-543 expression via binding the promoter region of miR-543. Furthermore, miR-543 upregulation promotes the expression of genes related to drug metabolism, including CYP3A4, which is involved in ruxolitinib metabolism. Our findings suggest miR-543 as a potentially novel biomarker for the prognosis of MF patients with a high risk of treatment resistance and as a potentially new target for the development of new treatment options The work in GAC’s laboratory was partly supported by NIH/National Center for Advancing Translational Sciences grant UH3TR00943-01, the NIH/National Cancer Institute (NCI) grant 1 R01 CA182905-01, U54 grant UPR/MDACC Partnership for Excellence in Cancer Research 2016 Pilot Project, Team Department of Defense grant CA160445P1, a Ladies Leukemia League grant, a Chronic Lymphocytic Leukemia Moonshot Flagship project, a Sister Institution Network Fund 2017 grant, and the Estate of C. G. Johnson, Jr. EFM was supported in part by award number P50 CA140388 from the NCI and by the NIH Clinical Research Loan Repayment Program. AMS was supported by Fundação para a Ciência e a Tecnologia through fellowship SFRH/BD/85968/2012. ZJZ’s work was supported by grants from the MPN Foundation and the Oklahoma Center for the Advancement of Science and Technology. DG, MPD, and IBN were supported in part by a Programul Opera¿ional Competitivitate grant nr35/01.09.2016, ID 37_796, titled “Clinical and economical impact of personalized targeted anti-mi-croRNA therapies in reconverting lung cancer chemoresistance” (CANTEMIR). NSDA was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo, BEPE 2016/09349-4.

The cancer-risk-associated rs6983267 single nucleotide polymorphism (SNP) and the accompanying long noncoding RNA CCAT2 in the highly amplified 8q24.21 region have been implicated in cancer predisposition, although causality has not been established. Here, using allele-specific CCAT2 transgenic mice, we demonstrate that CCAT2 overexpression leads to spontaneous myeloid malignancies. We further identified that CCAT2 is overexpressed in bone marrow and peripheral blood of myelodysplastic/myeloproliferative neoplasms (MDS/MPN) patients. CCAT2 induces global deregulation of gene expression by down-regulating EZH2 in vitro and in vivo in an allele-specific manner. We also identified a novel non-APOBEC, non-ADAR, RNA editing at the SNP locus in MDS/MPN patients and CCAT2-transgenic mice. The RNA transcribed from the SNP locus in malignant hematopoietic cells have different allelic composition from the corresponding genomic DNA, a phenomenon rarely observed in normal cells. Our findings provide fundamental insights into the functional role of rs6983267 SNP and CCAT2 in myeloid malignancies.

Background: Prior work from our group has shown that fibrocytes, the cells driving bone marrow (BM) fibrosis in patients with primary myelofibrosis (PMF), are neoplastic (clonal) and derived from monocytes (Verstovsek, J Exp Med 2016). These findings led to the clinical development of PRM-151 (recombinant human pentraxin-2) as an anti-fibrotic agent for patients with myelofibrosis (MF) (Verstovsek, EHA 2019). Our observations were extended by others to show that thrombopoietin receptor (MPL) activation induces fibrocyte differentiation and that blood monocytes highly expressing MPL and signaling lymphocyte activation molecule family member 7 (SLAMF7) were possible fibrocyte precursors (Maekawa, Leukemia 2018). Furthermore, patients with JAK2V617F+ MF have a significantly elevated SLAMF7 high monocyte percentage, which correlates with the JAK2V617F allele burden (Maekawa, Blood 2019). Finally, elotuzumab, a SLAMF7-targeting monoclonal antibody, inhibited the differentiation of MF patient-derived fibrocytes in vitro and romiplostim-induced MF and splenomegaly in vivo. Study design and methods: This is a single-institution, investigator-initiated, pilot phase 2 study of elotuzumab monotherapy in patients with JAK2V617F+ PMF or post-polycythemia vera/essential thrombocythemia MF who need treatment but are not candidates for JAK inhibitor therapy. Baseline BM fibrosis grade must be 2 or 3 per the European consensus (Thiele, Haematologica 2005). Prior JAK inhibitor treatment is permitted. Elotuzumab is dosed intravenously weekly at 10 mg/kg per dose for the first 8 doses, followed by 20 mg/kg every 4 weeks, per the label for its use in multiple myeloma in combination with pomalidomide and dexamethasone. Patients may continue elotuzumab until disease progression or unacceptable toxicity, up to a maximum of 36 cycles. Premedication and management of infusion reactions are carried out according to the elotuzumab package insert. Spleen and liver sizes are measured by palpation and the MPN-SAF-TSS questionnaire (Emanuel, J Clin Oncol 2012) is administered on day 1 of each cycle. Patients receive a BM biopsy at screening and every 6 cycles while on-study. Plasma cytokines are measured at baseline and every 3 cycles while on-study. The primary endpoint is overall response rate according to the revised IWG-MRT-ELN criteria (Tefferi, Blood 2013). A total of 15 patients are planned to be enrolled. Elotuzumab is provided by Bristol-Myers Squibb. Adverse events are graded according to the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. The method of Thall, Simon and Estey (Thall, Stat Med 1995) is used for toxicity monitoring. Correlative studies: These include quantification of SLAMF7 highCD16 neg circulating monocytes by flow cytometry, measurement of serum interleukin-1 receptor alpha (IL-1Rα) concentrations and correlation of these with each other and with the mutant JAK2 allele burden, culture of human fibrocytes from peripheral blood mononuclear cells (PBMCs) in vitro, engraftment of BM cells from patients in non-obese diabetic, severe combined immunodeficient gamma (NSG) mice, and quantitation of fibrocytes in the BM of participants at baseline and every 6 cycles. Current status: The study (clinicaltrials.gov identifier: NCT04517851) is ongoing; 2 participants have been enrolled and treated thus far. Updated enrollment information will be provided. Disclosures Bose: Astellas: Research Funding; Sierra Oncology: Honoraria; Constellation Pharmaceuticals: Research Funding; Novartis: Honoraria; Celgene Corporation: Honoraria, Research Funding; Incyte Corporation: Honoraria, Research Funding; NS Pharma: Research Funding; Promedior: Research Funding; Blueprint Medicines: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Kartos Therapeutics: Honoraria, Research Funding; CTI BioPharma: Honoraria, Research Funding; Pfizer: Research Funding. Jain: TG Therapeutics: Honoraria; Janssen: Honoraria; Servier: Honoraria, Research Funding; Aprea Therapeutics: Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Beigene: Honoraria; Adaptive Biotechnologies: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Precision Biosciences: Honoraria, Research Funding; ADC Therapeutics: Honoraria, Research Funding; Pfizer: Research Funding; Cellectis: Honoraria, Research Funding; Fate Therapeutics: Research Funding; AstraZeneca: Honoraria, Research Funding; Incyte: Research Funding; Pharmacyclics: Research Funding. Pemmaraju: Roche Diagnostics: Consultancy; ASH Communications Committee: Membership on an entity's Board of Directors or advisory committees; ASCO Leukemia Advisory Panel: Membership on an entity's Board of Directors or advisory committees; Samus: Other, Research Funding; Springer Science + Business Media: Other; HemOnc Times/Oncology Times: Membership on an entity's Board of Directors or advisory committees; Dan's House of Hope: Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy; Clearview Healthcare Partners: Consultancy; Blueprint Medicines: Consultancy; Protagonist Therapeutics, Inc.: Consultancy; Sager Strong Foundation: Other; Cellectis S.A. ADR: Other, Research Funding; Daiichi Sankyo, Inc.: Other, Research Funding; Plexxicon: Other, Research Funding; CareDx, Inc.: Consultancy; Aptitude Health: Consultancy; MustangBio: Consultancy, Other; Abbvie Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Celgene Corporation: Consultancy; Stemline Therapeutics, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; LFB Biotechnologies: Consultancy; Novartis Pharmaceuticals: Consultancy, Other: Research Support, Research Funding; Incyte: Consultancy; Affymetrix: Consultancy, Research Funding; Bristol-Myers Squibb Co.: Consultancy; ImmunoGen, Inc: Consultancy; Pacylex Pharmaceuticals: Consultancy. Kantarjian: Amgen: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; NOVA Research: Honoraria; Precision Biosciences: Honoraria; Astra Zeneca: Honoraria; KAHR Medical Ltd: Honoraria; Ipsen Pharmaceuticals: Honoraria; Daiichi-Sankyo: Research Funding; Jazz: Research Funding; Immunogen: Research Funding; BMS: Research Funding; Astellas Health: Honoraria; AbbVie: Honoraria, Research Funding; Ascentage: Research Funding; Novartis: Honoraria, Research Funding; Aptitude Health: Honoraria; Taiho Pharmaceutical Canada: Honoraria. Verstovsek: Blueprint Medicines Corp: Research Funding; Promedior: Research Funding; PharmaEssentia: Research Funding; Protagonist Therapeutics: Research Funding; CTI BioPharma: Research Funding; Celgene: Consultancy, Research Funding; Genentech: Research Funding; NS Pharma: Research Funding; Ital Pharma: Research Funding; Incyte Corporation: Consultancy, Research Funding; Gilead: Research Funding; Sierra Oncology: Consultancy, Research Funding; Roche: Research Funding; AstraZeneca: Research Funding; Novartis: Consultancy, Research Funding; Constellation: Consultancy; Pragmatist: Consultancy. OffLabel Disclosure: Elotuzumab is a monoclonal antibody targeting SLAMF7, previously known as CS-1. It is approved for the treatment of multiple myeloma in combination with an IMiD and dexamethasone. This trial studies it as a single agent in patients with myelofibrosis.

Primary myelofibrosis (MF), post-polycythemia vera (PV) MF, and post-essential thrombocytosis MF are myeloproliferative neoplasms (MPNs) characterized by progressive bone marrow (BM) fibrosis. A recent study suggested that glioma-associated oncogene-1 (GLI1), a downstream effector of the embryonic Hedgehog pathway, is implicated in the pathogenesis of BM fibrosis in MF. Because we and other investigators have found that monocyte-derived fibrocytes, rather than mesenchymal stromal cells (MSCs), induce BM fibrosis in MF, we sought to determine the role of GLI1 in MF fibrocytes. To do this, we analyzed BM biopsy sections of patients with MF using multiplex fluorescence immunohistochemistry and detected high levels of GLI1 in CD45+/CD68+/procollagen I+ fibrocytes and low levels of GLI1 in CD90+/CD105+ MSCs (P=0.009 and P=0.002, respectively). Using immunostaining, RNA in situ hybridization, gene expression, and western immunoblotting analyses of cultured BM fibrocytes or MSCs, we observed significantly higher levels of GLI1 and GLI1-induced matrix metalloproteases (MMP) 2 and 9 in MF fibrocytes than in MF MSCs or normal BM-derived fibrocytes (P

Prognostic scoring systems for primary myelofibrosis (PMF) are not accurate in patients with post-essential thrombocythemia and post-polycythemia vera myelofibrosis (PET-MF; PPV-MF). Given the paucity of data describing the clinical characteristics, disease course and outcomes of these patients, we sought to describe and compare the clinical characteristics and outcomes of 755 patients with PMF, 181 with PPV-MF, and 163 with PET-MF referred to our institution between 1984 and 2013. The median follow-up was 31 months, and 56% (n=616) patients had died. Over an observation period of 3,502 person-years, 11% of patients had progression to AML, with similar rates among groups. The proportion of patients with transfusion dependency (higher in PMF), leukocytosis and systemic symptoms (higher in PPV-MF), and thrombocytopenia (higher in PMF, PPV-MF) differed among groups. Median overall survival (OS) was longest in PET-MF patients (73 mo vs 45 mo (PMF) vs 48 mo (PPV-MF), p

To confirm that neoplastic monocyte-derived collagen- and fibronectin-producing fibrocytes induce bone marrow (BM) fibrosis in primary myelofibrosis (PMF), we injected PMF BM-derived fibrocyte-precursor CD14+/CD34- monocytes into the tail vein of NOD-SCID-γ (NSG) mice. PMF BM-derived CD14+/CD34- monocytes engrafted and induced a PMF-like phenotype with splenomegaly, myeloid hyperplasia with clusters of atypical megakaryocytes, persistence of the JAK2V617F mutation, and BM and spleen fibrosis. As control we used normal human BM-derived CD14+/CD34- monocytes. These monocytes also engrafted and gave rise to normal megakaryocytes that, like PMF CD14+/CD34--derived megakaryocytes, expressed HLA-ABC and human CD42b antigens. Using 2 clonogenic assays we confirmed that PMF and normal BM-derived CD14+/CD34- monocytes give rise to megakaryocyte colony-forming cells, suggesting that a subpopulation BM monocytes harbors megakaryocyte progenitor capacity. Taken together, our data suggest that PMF monocytes induce myelofibrosis-like phenotype in immunodeficient mice and that PMF and normal BM-derived CD14+/CD34- monocytes give rise to megakaryocyte progenitor cells.

We previously demonstrated that peripheral blood (PB) is a reliable source for testing JAK2V617F mutation in patients with myelofibrosis (MF); saliva has also been tested to detect such mutation, however its diagnostic accuracy as compared to PB has not been validated. In this study, we prospectively tested 167 patients with MF for JAK2V617F mutation, using both saliva and PB collected at the same time from each patient. The concordance between the 2 sources was 96%, with a sensitivity of 100% and a specificity of 90%. The only factor associated with false positivity on saliva was ongoing transfusion dependency. JAK2V617F testing using saliva is a simple, non-invasive, and potentially a more reliable method than PB for measuring JAK2 status and assessing V617F allelic burden in patients with transfusion dependency.

Myeloproliferative neoplasms with myelofibrosis (MPN-MF) demonstrate constitutive activation of Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling that responds to treatment with the JAK1 and 2 kinase inhibitor (JAKi) ruxolitinib. However, MPN-MF often progresses (~20%) to secondary acute myeloid leukemia (sAML), where standard induction chemotherapy or ruxolitinib is relatively ineffective, necessitating the development of novel therapeutic approaches. In the present studies, we demonstrate that treatment with BET (bromodomain and extraterminal) protein inhibitor (BETi), for example, JQ1, inhibits growth and induces apoptosis of cultured and primary, patient-derived (PD), post-MPN sAML blast progenitor cells. Reverse-phase protein array, mass-cytometry and Western analyses revealed that BETi treatment attenuated the protein expressions of c-MYC, p-STAT5, Bcl-xL, CDK4/6, PIM1 and IL-7R, whereas it concomitantly induced the levels of HEXIM1, p21 and BIM in the sAML cells. Co-treatment with BETi and ruxolitinib synergistically induced apoptosis of cultured and PD sAML cells, as well as significantly improved survival of immune-depleted mice engrafted with human sAML cells. Although BETi or heat shock protein 90 inhibitor (HSP90i) alone exerted lethal activity, cotreatment with BETi and HSP90i was synergistically lethal against the ruxolitinib-persister or ruxolitinib-resistant sAML cells. Collectively, these findings further support in vivo testing of BETi-based combinations with JAKi and HSP90i against post-MPN sAML cells.

Estrov and collaborators examine the role of fibrocytes in primary myelofibrosis and propose a novel therapeutic approach., Primary myelofibrosis (PMF) is a fatal neoplastic disease characterized by clonal myeloproliferation and progressive bone marrow (BM) fibrosis thought to be induced by mesenchymal stromal cells stimulated by overproduced growth factors. However, tissue fibrosis in other diseases is associated with monocyte-derived fibrocytes. Therefore, we sought to determine whether fibrocytes play a role in the induction of BM fibrosis in PMF. In this study, we show that BM from patients with PMF harbors an abundance of clonal, neoplastic collagen- and fibronectin-producing fibrocytes. Immunodeficient mice transplanted with myelofibrosis patients’ BM cells developed a lethal myelofibrosis-like phenotype. Treatment of the xenograft mice with the fibrocyte inhibitor serum amyloid P (SAP; pentraxin-2) significantly prolonged survival and slowed the development of BM fibrosis. Collectively, our data suggest that neoplastic fibrocytes contribute to the induction of BM fibrosis in PMF, and inhibiting fibrocyte differentiation with SAP may interfere with this process.

Transcriptional regulators (TFs) involved in cell-growth, differentiation and survival of AML stem/progenitor cells (LSCs) include RUNX1, PU.1, CEBPα, c-Myb and c-Myc. LSD1 (KDM1A) is an FAD-dependent amine-oxidase that demethylates mono and dimethyl histone H3 lysine 4 (H3K4Me1 and H3K4Me2). LSD1 is part of the repressor complexes involving GFI1, CoREST and HDAC1/2, that regulate active super-enhancers/enhancers (SEs/Es) and their target genes, mediating transcriptional repression and differentiation block in LSCs. GFI1 is a zinc-finger transcriptional repressor involved in AML development and differentiation. GFI1 contains an N-terminal domain through which it binds to the CoREST/LSD1/HDAC1/2 complex to regulate differentiation in LSCs. CRISPR-suppressor scanning revealed that enzymatic activity of LSD1 was not required for LSC differentiation, instead disruption of binding of LSD1 to GFI1 and CoREST induced differentiation in LSCs. LSD1 and GFI1 expression correlates with worse prognosis in MDS/AML. In present studies, we demonstrate first-time ever that knockout (KO) or degradation of LSD1 utilizing CRISPR-Cas9 or LSD1-FKBP12(F36V) and dTAG-13, respectively, disrupted LSD1-binding to GFI1/1B and CoREST, inhibiting colony growth and inducing differentiation markers (CD86 and CD11b) and morphologic differentiation of AML and post-MPN sAML blast progenitor cells (BPCs). CRISPR-mediated knockout of LSD1 in the AML OCI-AML5 and sAML SET2 cells significantly increased the permissive H3K4Me2/3-marked chromatin, reduced H3K27Ac occupancy at SEs/Es (by ChIP-Seq), especially of c-Myc and CDK6, as well as repressed DNMT1, CoREST, c-Myc, CDK6, and c-KIT, while inducing GFI1, PU.1, CEBPα, p21, CD11b, and CD86 levels (log2 -fold change by RNA-Seq and by Western analyses). This correlated with growth inhibition, % differentiation and apoptosis of AML and sAML cells. CRISPR-mediated GFI1-KO ± the irreversible LSD1 inhibitor (LSD1i) (INCB059872, INCB), repressed GFI1 levels, yet enhanced expressions of PU.1, p21 and CD11b and significantly increased % morphologic differentiation. Treatment with INCB (0.25 to 1.0 µM) also disrupted binding of LSD1 to GFI1 and to CoREST, increased GFI1/1B and PU.1 and repressed c-Myc protein levels, while significantly inhibiting colony growth, inducing differentiation and loss of viability of AML and post-MPN sAML (SET2 and HEL92.1.7) cells, as well as patient-derived AML and post-MPN sAML blasts (p < 0.01). Following INCB treatment, ATAC-Seq analysis demonstrated gained peaks in GFI1 and PU.1-target genes. Following H3K27Ac ChIP-seq analysis rank-ordering of SEs (ROSE) plot highlighted active SEs of RUNX1, GFI1, BCL2, PU.1, IRF8 and SMYD3, accompanied by increased H3K27Ac occupancy at the chromatin of GFI1 and PU.1 targets. Notably, INCB treatment also increased BRD4 occupancy, especially at the GFI1 and PU.1-target genes. RNA-Seq analysis showed that INCB treatment perturbed mRNA expressions, with positive normalized enrichment scores (NES) for interferon α, inflammatory-response, GFI1-targets and E2F-target gene-sets, and negative NES for c-Myc-targets and oxidative-phosphorylation gene-sets. RNA-Seq analyses of INCB-treated compared to untreated OCI-AML5 and SET-2 cells also demonstrated log2 fold-increase in the mRNA expressions of GFI1, PU.1 and CEBPα target-genes. Utilizing a protein domain-scanning CRISPR-Cas9 sgRNA screen followed by LSD1i treatment, present studies also demonstrate co-dependencies, including BRD4, in AML cells. BET inhibitor (BETi) treatment also depleted LSD1 protein levels, and co-treatment with the BETi OTX015 and INCB induced synergistic lethality in AML and post-MPN sAML blasts (Combination Indices < 1.0). Pre-treatment with INCB re-sensitized JAKi-resistant sAML cells to ruxolitinib-induced apoptosis and BETi-resistant post-MPN sAML cells to BETi-induced apoptosis. Notably, co-treatment with INCB (1.5 mg/kg) and ruxolitinib (20 mg/kg) or OTX015 (50 mg/kg), administered orally for 21 days, compared to ruxolitinib alone or vehicle control, significantly reduced the sAML burden and improved survival of immune-depleted mice engrafted with luciferized sAML HEL92.1.7 xenografts (p < 0.01). Collectively, these findings support further pre-clinical development of LSD1i-based combinations with ruxolitinib and BETi against post-MPN sAML. Disclosures Bose: CTI BioPharma: Honoraria, Research Funding; NS Pharma: Research Funding; Celgene Corporation: Honoraria, Research Funding; Pfizer, Inc.: Research Funding; Constellation Pharmaceuticals: Research Funding; Astellas Pharmaceuticals: Research Funding; Blueprint Medicines Corporation: Honoraria, Research Funding; Promedior, Inc.: Research Funding; Incyte Corporation: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kartos Therapeutics: Honoraria, Research Funding. Kadia:Incyte: Research Funding; Pulmotec: Research Funding; Cellenkos: Research Funding; Celgene: Research Funding; Amgen: Research Funding; Genentech: Honoraria, Research Funding; JAZZ: Honoraria, Research Funding; Cyclacel: Research Funding; Novartis: Honoraria; Ascentage: Research Funding; Astellas: Research Funding; Pfizer: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Astra Zeneca: Research Funding; BMS: Honoraria, Research Funding. Verstovsek:CTI Biopharma Corp: Research Funding; AstraZeneca: Research Funding; Sierra Oncology: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Incyte Corporation: Consultancy, Research Funding; PharmaEssentia: Research Funding; Blueprint Medicines Corp: Research Funding; NS Pharma: Research Funding; Roche: Research Funding; Gilead: Research Funding; Protagonist Therapeutics: Research Funding; Promedior: Research Funding; Genentech: Research Funding; Celgene: Consultancy, Research Funding; ItalPharma: Research Funding.

Protein arginine methyltransferase 5 (PRMT5) is the major type II PRMT that catalyzes the formation of symmetrical dimethyl arginine (SDMA) on protein substrates and plays important roles in various cellular pathways including tumorigenesis. PRMT5 can methylate histones H3 and H4, thereby leading to repression of tumor suppressor genes at specific loci. PRMT5 also regulates gene expression on a global level by methylating and altering the function of transcription factors such as p53, E2F-1, NF-κB and others. Additionally, PRMT5 has been shown to interact with members of the spliceosome complex and regulate pre-mRNA processing of key target genes. In this study, we describe the in vitro and in vivo activity of PRT543, a novel, potent and selective inhibitor of PRMT5, in hematological and solid tumor models. In a scintillation proximity based radiometric assay, PRT543 inhibited the methyltransferase activity of the PRMT5/MEP50 complex with an IC50 of 10.8 nM. It was also highly selective against a panel of 36 other methyltransferases. PRT543 robustly inhibited cell proliferation in a panel of >50 cancer cell lines, representing both solid tumors and cancers of hematological origin, in a concentration-dependent manner with IC50 values ranging from 10 - 1000 nM. This anti-proliferative activity correlated with a reduction of symmetrically dimethylated SmD3 protein, a known PRMT5 substrate, demonstrating effective inhibition of PRMT5 enzymatic activity in cells. PRT543 demonstrated good oral bioavailability and favorable pharmacokinetic properties. Oral administration of this compound led to significant tumor growth inhibition in several subcutaneous mouse xenograft models including mantle cell lymphoma (Granta-519, Z-138), acute myeloid leukemia (MV4-11, SET2, HEL), small cell lung cancer (NCI-H1048) and bladder cancer (5637) at well-tolerated doses. This in vivo activity was accompanied by a corresponding decrease in symmetrically dimethylated SmD3 in tumor tissue collected from the treated animals. PRT543 was also tested in combination with other approved targeted therapies both in vitro and in vivo. Combining PRT543 with the BCL2 inhibitor, venetoclax, revealed a potent synergistic interaction in models of leukemia and lymphoma. Further ex vivo testing in genetically-defined primary patient tumor samples is ongoing. PRT543 is currently under evaluation in a Phase I clinical trial in patients with advanced solid tumors and hematological malignancies (NCT03886831). Citation Format: Neha Bhagwat, Yang Zhang, Hong Lin, Min Wang, Dave Rominger, Tom Emm, Divya Chugani-Mahtani, Dimitrios Angelis, Rupa Shetty, Raul Leal, William Gowen-MacDonald, Alexander Grego, Juan Luengo, Taghi Manshouri, Friederike Pastore, Ross L. Levine, Srdan Verstovsek, Bruce Ruggeri, Peggy Scherle, Kris Vaddi. Preclinical characterization of PRT543, a potent and selective inhibitor of protein arginine methyltransferase 5 (PRMT5), with broad antitumor activity in in vitro and in vivo models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2915.

Transformation of post-myeloproliferative neoplasms into secondary (s) AML exhibit poor clinical outcome. In addition to increased JAK-STAT and PI3K-AKT signaling, post-MPN sAML blast progenitor cells (BPCs) demonstrate increased nuclear β-catenin levels and TCF7L2 (TCF4) transcriptional activity. Knockdown of β-catenin or treatment with BC2059 that disrupts binding of β-catenin to TBL1X (TBL1) depleted nuclear β-catenin levels. This induced apoptosis of not only JAKi-sensitive but also JAKi-persister/resistant post-MPN sAML BPCs, associated with attenuation of TCF4 transcriptional targets MYC, BCL-2, and Survivin. Co-targeting of β-catenin and JAK1/2 inhibitor ruxolitinib (rux) synergistically induced lethality in post-MPN sAML BPCs and improved survival of mice engrafted with human sAML BPCs. Notably, co-treatment with BET protein degrader ARV-771 and BC2059 also synergistically induced apoptosis and improved survival of mice engrafted with JAKi-sensitive or JAKi-persister/resistant post-MPN sAML cells. These preclinical findings highlight potentially promising anti-post-MPN sAML activity of the combination of β-catenin and BETP antagonists against post-MPN sAML BPCs.

Although most patients with myelofibrosis (MF) derive benefit from ruxolitinib, some are refractory, have a suboptimal response, or quickly lose their response. To identify genes that may predict response to ruxolitinib, we performed targeted next-generation sequencing (NGS) of a panel of 28 genes recurrently mutated in hematologic malignancies in a cohort of patients with MF who were treated with ruxolitinib in a phase 1/2 study. We also tested for CALR deletions by standard polymerase chain reaction methods. Ninety-eight percent of patients had a mutation in ≥1 gene. Seventy-nine (82.1%) patients had the JAK2(V617F) mutation, 9 (9.5%) had CALR mutations (7 type 1, 2 type 2), 3 (3.1%) had MPL mutations, and 4 (4.2%) were negative for all 3. ASXL1/JAK2 and TET2/JAK2 were the most frequently comutated genes. Mutations in NRAS, KRAS, PTPN11, GATA2, TP53, and RUNX1 were found in

We previously demonstrated that peripheral blood (PB) is a reliable source for testing JAK2

Therapy-related myeloid neoplasms, such as myelodysplastic syndromes (t-MDSs) and acute myeloid leukemia (t-AML), account for 10% to 20% of all myeloid neoplasms and are recognized as a distinct subgroup according to 2008 World Health Organization (WHO) criteria.[1][1] Although t-MDS/t-AML are often