scholarly journals Selective Targeting of Histone Deacetylase 11 Disables Metabolism of Myeloproliferative Neoplasms

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 474-474
Author(s):  
Vasundhara Sharma ◽  
Lanzhu Yue ◽  
Nathan P. Horvat ◽  
Agni Christodoulidou ◽  
Afua Adutwumwa Akuffo ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Myeloproliferative Neoplasms ◽  
Hdac Inhibitors ◽  
Leukemia Cell ◽  
Cell Types ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Leukemia Cell Lines

Introduction: Acetylated histone and non-histone proteins are pharmacologic targets for both solid and hematological cancers including myeloproliferative neoplasms (MPNs), a group of clonal hematological malignancies driven by aberrant JAK2/STAT signaling. MPNs are characterized by epigenetic alterations, including aberrant acetylation, which makes this disease particularly interesting for targeting with HDAC inhibitors. Four classes of histone deacetylases (Class I-IV HDACs) regulate gene transcription and modulate cellular processes that drive the initiation and progression of cancer. Pan-HDAC and class I-selective HDAC inhibitors have gained traction in clinical settings, yet we reasoned that specific targeting of the 18 distinct HDAC proteins may establish roles for select HDACs as therapeutic vulnerabilities in MPNs. Methods: To explore the roles of individual HDACs in MPN, we first conducted an inhibitor screen of compounds having distinct HDAC selectivity based on electrophoretic mobility shift assays with full-length human HDAC proteins expressed in baculovirus and unique peptide substrates. Ultra-specific HDAC6 compounds were initially targeted for analysis based on its previously defined role in HSP90-mediated JAK2 stabilization and translation. Survival of MPN cell line models, MPN patient samples, leukemia cell lines, and MPN disease progression in mice transplanted with Hdac6-/-, and Hdac11-/- hematopoietic stem cells (HSCs) transduced with the MPLW515L oncogene, as well as Tg-Hdac11-eGfp mice were used to show the role of HDAC6 and HDAC11 in oncogene-driven and homeostatic hematopoiesis. As further proof of specificity, HDAC6 and HDAC11 were genetically ablated in MPN model cell lines using either RNA interference or inducible shRNA. For HDAC11 substrate identification, a combination of RNA-seq, acetylated proteome (SILAC), global metabolomics (LC-MS), Seahorse metabolic assays (Agilent Technologies), enzymatic assays, and acetylation-specific immunoblotting and mutation profiling were performed (Fig. 1). Results: Despite the established interplay between HDAC6, HSP90 and JAK2, neither a highly selective HDAC6 inhibitor, HDAC6 silencing, nor the Hdac6 deficiency suppressed MPN pathogenesis, although there were clear effects on the acetylation of α-tubulin, a well characterized HDAC6-selective substrate. Intriguingly, both inhibition of HDAC11 activity with highly-specific HDAC11 inhibitors and silencing HDAC11 using an inducible validated shRNA, identified HDAC11 as a therapeutic vulnerability for multiple human MPN cell lines. The Tg-Hdac11-eGFP reporter mice showed that HDAC11 is expressed in several hematopoietic cell types, including myeloid cells, erythroblasts, and megakaryocytes. Thus, Hdac11-/- and Hdac11+/+MPLWT bone marrow were examined for steady-state hematopoiesis and transplantation chimerism. These studies demonstrated that HDAC11 does not contribute to homeostatic or transplantated bone marrow reconstitution. However, in the oncogenic MPL model, recipient mice transplanted withoncogenic MPLW515L-expressing Hdac11-deficient HSCs displayed markedly impaired cytokine-independent colony-formation, had less fibrosis, and displayed improved survival in primary and secondary MPN hematopoietic stem cell transplantation; thus HDAC11 contributes to MPN pathogenesis (Fig. 1). Studies in additional leukemia cell lines, including THP-1, HL-60, and mantle lymphoma cell lines, but not in Ramos or K562 cells, established that HDAC11 contributes to oncogene-driven events in other cell types. Mechanistically, RNA-seq, SILAC proteomics, and metabolic profiling revealed that HDAC11 controls aerobic glycolysis by deacetylating Lys343 of the glycolytic enzyme enolase-1 (ENO1), functionally inactivating ENO1. Finally, the effects of targeting HDAC11 on metabolism were augmented by blocking compensatory pathways of oxidative phosphorylation that are induced via JAK2V617Fand MPLW515L oncogenic signaling. Conclusions: Our comprehensive screens of HDAC inhibitors, coupled with our biological, in vivo and molecular studies, indicate that HDAC11 is an attractive and potent target for disabling MPN metabolism and pathogenesis. These finding support the rationale for further development of clinical HDAC11 inhibitors for the treatment of metabolically-active cancers such as MPNs. Disclosures Pinilla Ibarz: Teva: Consultancy; TG Therapeutics: Consultancy; Sanofi: Speakers Bureau; Bayer: Speakers Bureau; Novartis: Consultancy; Bristol-Myers Squibb: Consultancy; Abbvie: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau. Reuther:Incyte Corporation: Research Funding. Levine:Loxo: Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Research Funding; Lilly: Honoraria; C4 Therapeutics: Membership on an entity's Board of Directors or advisory committees; Isoplexis: Membership on an entity's Board of Directors or advisory committees; Imago Biosciences: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Gilead: Consultancy; Celgene: Consultancy, Research Funding; Qiagen: Membership on an entity's Board of Directors or advisory committees; Prelude Therapeutics: Research Funding; Amgen: Honoraria. Verma:BMS: Research Funding; Janssen: Research Funding; Stelexis: Equity Ownership, Honoraria; Acceleron: Honoraria; Celgene: Honoraria. Epling-Burnette:Incyte Corporation: Research Funding; Celgene Corporation: Patents & Royalties, Research Funding; Forma Therapeutics: Research Funding.

scholarly journals The 3-Drug Combination Treatment ART838, ABT199 Plus Sorafenib Is Effective Against AML Xenografts, Possibly Via Cooperative Targeting of MCL1

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 4044-4044
Author(s):  
Blake S Moses ◽  
Jennifer Fox ◽  
Xiaochun Chen ◽  
Samantha McCullough ◽  
Sang Ngoc Tran ◽  
...  
Keyword(s):  
Acute Leukemia ◽  
Board Of Directors ◽  
Cell Lines ◽  
Drug Combination ◽  
Research Funding ◽  
Leukemia Cell ◽  
Advisory Committees ◽  
Leukemia Cell Lines ◽  
Equity Ownership

Abstract Antimalarial artemisinins have broad antineoplastic activity in vitro, are well tolerated and inexpensive, and can be parenterally or orally administered in humans. Artemisinin-derived trioxane diphenylphosphate dimer 838 (ART838; a potent artemisinin-derivative) inhibited acute leukemia growth in vivo and in vitro, at doses where normal human CD34+ hematopoietic stem-progenitor cell clonogenicity was essentially unaffected (Fox et al, Oncotarget 2016, PMID: 26771236). In our focused drug combination screen for drugs that synergize with ART838, the only BCL2 inhibitors in the screen library of 111 emerging antineoplastic compounds, navitoclax (ABT737) and venetoclax (ABT199; FDA-approved), were identified as 2 of the top 3 candidates. Synergies between ART838 and BCL2 inhibitors were validated in multiple acute leukemia cell lines and primary cases. This ART838-BCL2 inhibitor synergy may be due to reduced levels of MCL1 protein that we and others have observed in multiple acute leukemia cell lines and primary cases treated with artemisinins (Budhraja et al, Clin Cancer Res 2017, PMID: 28974549). Treatment of acute leukemia xenografts with the ART838 plus ABT199 combination reduced leukemia growth rates and prolonged survivals, compared to vehicle or either ART838 or ABT199 alone. To add to the efficacy of this ART838 plus ABT199 treatment regimen, we sought to rationally add a third low-toxicity active antileukemic agent. Sorafenib (SOR; FDA-approved) inhibits multiple kinases which may mediate its antileukemic activity, with the importance of the targets varying from case to case; e.g. FLT3 is an important target in many AMLs. In addition, several reports have found that SOR reduces MCL1 protein stability and translation through inhibition of the ERK and PI3K pathways (Wang et al, Clin Cancer Res 2016, PMID: 26459180; Huber et al, Leukemia 2011, PMID: 21293487). In all acute leukemia cell lines tested, we observed large reductions in MCL1 protein levels with SOR treatment, which may further rationalize the addition of SOR to our ART838 plus ABT199 antileukemic regimen. We had previously observed strong in vitro synergy between ART838 and SOR (PMID: 26771236). Treatment of acute leukemia xenografts with the ART838 plus SOR combination reduced leukemia xenograft growth rates and prolonged survivals, compared to single drugs. Mice bearing luciferase-labelled acute leukemia xenografts were treated (PO daily x5) with single drug or 2-drug or 3-drug combinations of ART838, ABT199, and SOR, each at their individual maximally tolerated doses. Treatment with this 3-drug combination caused rapid regression of luciferase-labelled MV4;11 AML xenografts (Fig 1A). The 5-day treatment cycles were repeated every other week, and mice receiving this 3-drug combination survived >4 times longer than vehicle-treated mice (Fig 1B). Mouse body weights were stable during treatment. Although myelosuppression is the human clinical dose-limiting toxicity of each of these 3 drugs, mouse blood cell counts during 3-drug combination treatment were in the normal range. Treatment of a luciferase-labelled primary AML leukemia xenograft with this 3-drug combination reduced leukemia growth more than the single drugs or 2-drug combinations (Fig 1C). Assessment of efficacy and pharmacokinetics-pharmacodynamics against diverse acute leukemia xenografts will test this combination of ART838, ABT199 plus SOR as a rational low-toxicity drug triad for treatment of acute leukemias and potentially other cancers. Disclosures Fox: Intrexon Corporation: Employment. Tyner:Genentech: Research Funding; Janssen: Research Funding; AstraZeneca: Research Funding; Gilead: Research Funding; Incyte: Research Funding; Constellation: Research Funding; Array: Research Funding; Takeda: Research Funding; Vivid Biosciences: Membership on an entity's Board of Directors or advisory committees; Aptose: Research Funding. Civin:ConverGene LLC: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; GPB Scientific LLC: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; 3DBioWorks Inc: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; BD (Becton Dickinson): Honoraria.

scholarly journals Development of Astatine-211 (211At)-Based Anti-CD123 Radioimmunotherapy for Acute Leukemias and Other CD123+ Hematologic Malignancies

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3341-3341
Author(s):  
George S. Laszlo ◽  
Johnnie J. Orozco ◽  
Allie R. Kehret ◽  
Margaret C. Lunn ◽  
Donald K. Hamlin ◽  
...  
Keyword(s):  
Acute Leukemia ◽  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Leukemia Cell ◽  
Hematologic Malignancies ◽  
Advisory Committees ◽  
Leukemia Cell Lines ◽  
Efficacy Studies

Abstract Background: Radioimmunotherapy (RIT) has long been pursued to improve outcomes in acute leukemia. Of current interest are alpha-particle emitting radionuclides as they deliver a very large amount of radiation over just a few cell diameters, enabling efficient and selective target cell kill. So far, alpha-emitters including astatine-211 (211At) have been primarily explored with monoclonal antibodies (mAbs) targeting CD45 or CD33 but their broad display on non-malignant target-expressing cells can lead to marked "on-target, off tumor cell" toxicities. To overcome this limitation, we developed a novel form of 211At-based RIT targeting CD123. CD123 is displayed widely on acute leukemia cells, including underlying leukemic stem cells, but is expressed only on a discrete subset of normal hematopoietic cells and is virtually absent on non-blood cells. Methods: We immunized BALB/c mice with peptides consisting of the extracellular domain of human CD123 to generate anti-CD123 mAbs. Flow cytometry-based assays with human acute leukemia cell lines were used to characterize binding of hybridoma supernatants and mAbs to CD123. mAbs were conjugated with isothiocyantophenethyl-ureido-closo-decaborate(2-) (B10), a boron cage molecule for subsequent astatination, and were then labeled with 211At. In vivo leukemia cell targeting ("biodistribution") and efficacy studies were conducted in immunodeficient NOD-Rag1 null IL2rɣ null/J (NRG) mice xenografted with MOLM-13 cells, a CD123+ human acute myeloid leukemia cell line. Results: Based on initial hybridoma screening studies, we selected 4 mAbs (10C4, 5G4, 11F11, and 1H8) for further characterization. Phenotyping studies with CD123+ and CD123- human acute leukemia cell lines (including CD123+ cell lines in which CD123 was deleted via CRISPR/Cas9) confirmed specific binding of all mAbs to human CD123 (binding intensity: 10C4>5G4=11F11=1H8), with 10C4 yielding a higher median fluorescence intensity than the widely used commercial anti-CD123 mAb clones, 7G3 and 6H6 (Figure 1). In vitro internalization with a panel of human acute leukemia cell lines studies demonstrated uptake of all mAbs by CD123+ target cells with a kinetic slower than that for anti-CD33 antibodies (typically, 30-50% of the anti-CD123 mAb internalized over 2-4 hours). All 4 anti-CD123 mAbs could be conjugated to B10 and subsequently labeled with 211At. Unlike a non-binding 211At-labeled control mAb, 211At-labeled anti-CD123 mAbs showed uptake at MOLM-13 flank tumors in NRG mice carrying MOLM-13 xenografts. After additional leukemia cell targeting studies to optimize the dosing of 10C4, we conducted proof-of-concept efficacy studies in NRG mice injected intravenously with luciferase-transduced MOLM-13 cells (disseminated leukemia model). Animals were either untreated or treated with 10 µCi, 20 µCi, or 40 µCi of 211At-labeled 10C4-B10 mAb (9-11 animals/group). This was followed by the infusion of bone marrow cells from donor mice as stem cell support 3 days later. As shown in Figure 2 and Figure 3, 211At-10C4-B10 led to a dose dependent decrease in tumor burden. Further, the treatment significantly prolonged survival compared to untreated animals (median survival: 49 days [40 µCi of 211At] vs. 31 days [10 µCi of 211At] vs. 21 days [Ctrl]; P<0.0001 for Ctrl vs. 10 µCi, P<0.004 for 10 µCi vs. 40 µCi), demonstrating potent in vivo anti-leukemia efficacy of a single dose of 211At-CD123 RIT. Conclusion: Our data support the further development of 211At-CD123 RIT for the treatment of patients with acute leukemia and other CD123+ hematologic malignancies. Figure 1 Figure 1. Disclosures Green: Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Cellectar Biosciences: Research Funding; GSK: Membership on an entity's Board of Directors or advisory committees; JANSSEN Biotech: Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno Therapeutics: Patents & Royalties, Research Funding; Legend Biotech: Consultancy; Neoleukin Therapeutics: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; SpringWorks Therapeutics: Research Funding. Walter: Kite: Consultancy; Janssen: Consultancy; Genentech: Consultancy; BMS: Consultancy; Astellas: Consultancy; Agios: Consultancy; Amphivena: Consultancy, Other: ownership interests; Selvita: Research Funding; Pfizer: Consultancy, Research Funding; Jazz: Research Funding; Macrogenics: Consultancy, Research Funding; Immunogen: Research Funding; Celgene: Consultancy, Research Funding; Aptevo: Consultancy, Research Funding; Amgen: Research Funding.

scholarly journals Bromodomain and Extra Terminal Domain (BET) Inhibitors Sensitize Chronic Myelomonocytic Leukemia (CMML) to PIM Inhibition Via Downregulation of Mir-33a

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4220-4220
Author(s):  
Christopher Letson ◽  
Alexis Vedder ◽  
Ariel Quintana ◽  
Phillip Liu ◽  
Brett Reid ◽  
...  
Keyword(s):  
Combination Therapy ◽  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Leukemia Cell ◽  
Leukemia Cells ◽  
Advisory Committees ◽  
Leukemia Cell Lines ◽  
Bet Inhibitors ◽  
Dose Dependent

CMML is a lethal myeloid neoplasm with no therapies that improve its dismal prognosis. Inhibition of BET family members has been proposed as a therapeutic strategy based on preclinical data identifying BRD4 as a therapeutic target in acute myeloid leukemia. However, despite potent on-target transcriptional remodeling, early phase clinical trials have demonstrated only modest activity secondary to a variety of resistance mechanisms. In ovarian cancer BET inhibitor (BETi) treated cells, compensatory upregulation and addiction to pro-survival kinase networks have been observed. Given that over 50% of CMML cases have mutations upregulating kinase signaling, we hypothesized that BETi resistance is mediated by these networks in CMML and can be targeted therapeutically. We tested this hypothesis by performing a limited screen of kinase inhibitors alone and in combination with the IC20 of the BETi INCB54329 in 8 human leukemia cell lines. This screen revealed that the IC50 of the PIM inhibitor (PIMi) INCB53914 decreased after co-treatment with BETi in a majority of the leukemia cell lines tested. Synergy was validated chemically in U937, TF1 and SKM1 leukemia cells using other selective inhibitors of BET and PIM. We next assessed the activity of the BET-PIM combination in 14-day colony formation assays with 10 unique CMML bone marrow mononuclear cell (BM-MNCs) patient samples(Fig. 1A). These studies revealed that combination therapy significantly suppressed clonogenicity versus BMNCs treated with vehicle or single drug alone. Finally, this synergy was validated in vivo in 36 patient derived xenografts (PDX) from 3 CMML patients, as manifest by reduced leukemic burden/engraftment in CMML PDX treated with combination therapy(Fig. 1B). To explore the mechanism by which BETi and PIMi therapeutically synergize we treated U937 and SKM1 leukemia cells with INCB54329 and measured mRNA and protein levels for all PIM isoforms. Surprisingly, we identified that PIM1 was increased following treatment with INCB54329, other BETi, or a JQ1-derived PROTAC (Fig. 1C). PIM1 upregulation was also manifest in INCB54329 persistor U937 leukemia cells generated by daily BETi treatment for 6 weeks. Testing across a broader panel of leukemia cell lines revealed an inverse correlation between PIM1 induction and decrease in the IC50 of PIMi following BETi treatment, suggesting PIM1 upregulation confers sensitivity to combination therapy. Consistent with this, isogenic SKM1 leukemia cells engineered to overexpress PIM1 were resistant to INCB54329 and were more sensitive to INCB53914 versus controls cells. Recent studies have demonstrated that inhibitory miRNAs, especially those located near super-enhancers, are suppressed by BET inhibition. Given that several miRNAs are known to control PIM1 expression, we hypothesized that paradoxical PIM1 upregulation following BETi treatment was due to down-regulation of select miRNAs. To test this, we treated our leukemia cell models with broad inhibitors of miRNA activity (i.e., AGO and Dicer inhibitors) and observed a dose dependent increase in PIM1 levels similar to that seen with BET inhibition(Fig. 1Di). Further, integrating public H3K27 CHIP-seq and miRNA super enhancer datasets and using computational prediction algorithms, we identified 6 candidate miRNAs that could regulate PIM1 and were predicted to be controlled by BET inhibitors. Of these, only miR-33a levels were reduced in a dose dependent manner in SKM1 cells by BETi treatment(Fig. 1Dii). This was confirmed by genetically silencing all BET proteins, which suppressed miR-33a levels in SKM1 leukemia cells. Finally, miR-33a mimics (but not control miRNAs) abolished BETi-induced upregulation of PIM1(Fig. 1Diii). Collectively, these studies established BET and PIM inhibition as a novel and potent combination therapy for CMML that is mediated by miR-33a-dependent upregulation of PIM1(Fig. 1E). Disclosures Liu: Incyte Corporation: Employment. Patnaik:Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees. Lancet:Daiichi Sankyo: Consultancy, Other: fees for non-CME/CE services ; Agios, Biopath, Biosight, Boehringer Inglheim, Celator, Celgene, Janssen, Jazz Pharmaceuticals, Karyopharm, Novartis: Consultancy; Pfizer: Consultancy, Research Funding. Komrokji:Novartis: Speakers Bureau; JAZZ: Speakers Bureau; JAZZ: Consultancy; Agios: Consultancy; Incyte: Consultancy; DSI: Consultancy; pfizer: Consultancy; celgene: Consultancy. Epling-Burnette:Incyte Corporation: Research Funding. List:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Haura:Incyte Corporation: Research Funding. Reuther:Incyte Corporation: Research Funding. Koblish:Incyte Corporation: Employment.

scholarly journals Loss of KDM6A Confers Drug Resistance in Acute Myeloid Leukemia

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 3935-3935
Author(s):  
Sophie M. Stief ◽  
Anna-Li Hanneforth ◽  
Raphael Mattes ◽  
Sabrina Weser ◽  
Binje Vick ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Board Of Directors ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Research Funding ◽  
Leukemia Cell ◽  
K562 Cells ◽  
Rna Seq ◽  
Advisory Committees ◽  
Leukemia Cell Lines

Abstract Acute myeloid leukemia (AML) is an aggressive hematologic cancer resulting from the malignant transformation of myeloid progenitors. Despite intensive chemotherapy, relapse caused by intrinsic or acquired drug resistance remains a major hurdle in the treatment of AML. Recently, we found KDM6A as a novel relapse-associated gene in a cohorte of 50 cytogenetically normal AML patients. KDM6A (or UTX) is a histone 3 lysine 27 (H3K27)-specific demethylase and a member of the COMPASS (complex of proteins associated with Set1)-like complex, which is important for chromatin enhancer activation. KDM6A is targeted by inactivating mutations in a variety of cancer types with frequency of occurrence ranging from 0.7 to 4% in AML. In this study, we used matched diagnosis and relapse samples from AML patients, patient-derived xenografts (PDX), and myeloid leukemia cell lines to investigate the status of KDM6A during disease progression and the implications of KDM6A loss regarding chemotherapy resistance. We found three AML patients with enrichment of KDM6A mutations at relapse and mutation-independent, relapse-specific loss of KDM6A expression in three additional AML patients. KDM6A mutations comprise deletions and point mutations and appear to be mainly loss-of-function mutations. In addition, we examined the mutation profile and KDM6A expression in patient-derived xenograft (PDX) samples from 8 relapsed AML patients. In 4/8 samples, KDM6A protein levels were low or completely lost. Due to the fact that all patients had received induction therapy including single or combination treatment with agents such as cytarabine (AraC), daunorubicin (DNR), and 6-thioguanine (6-TG), we hypothesized that loss of KDM6A confers resistance to chemotherapy. To exclude gender-specific effects (KDM6A escapes X inactivation leading to higher levels in females), we compared male KDM6A knockout (KO) with WT leukemia cell lines and found increased AraC resistance in the KDM6A KO cells (unpaired, two-tailed Student's t-test; P=0.0441). In addition, we treated two relapsed PDX AML cells of the same gender, AML 491 (KDM6A WT and strong expression) and AML 393 (KDM6A mutation and weak expression) with AraC for 72h in vitro and found significantly increased AraC resistance in the KDM6A-mutant PDX AML 393 cells (P=0.016). To further investigate whether reduced expression or loss of KDM6A leads to increased resistance towards multiple drugs, we silenced KDM6A expression by shRNA or CRISPR/Cas9 in K562 and MM-1 cells. Compared to control, KDM6A knockdown (KD) and KO K562 cells showed a strong proliferative advantage after AraC and DNR but not 6-TG treatment. A similar drug resistance phenotype was observed in KDM6A KO MM-1 cells. To unravel the mechanism of drug resistance, we performed RNA-Seq analysis in K562 cells treated with siRNA or shRNA against KDM6A under native conditions and after AraC (150nM) treatment for 72h. We compared these differentially expressed genes with known key candidate genes in AraC, DNR, and 6-TG metabolic pathway and found that ENT1 was consistently downregulated in KDM6A KD cells in both siRNA- and shRNA-mediated RNA-Seq screenings. Decreased ENT1 levels were also detected in KDM6A KO K562 single cell clones. ENT1 (also known as SLC29A1) is a membrane transporter relevant for the cellular uptake of nucleosides and its analogues. Competitive inhibition of ENT1 by the small molecule antagonist NBMPR lead to decreased sensitivity towards AraC but not DNR and 6-TG suggesting that increased AraC resistance in KDM6A KO cells is caused, at least partially, by downregulation of ENT1. To elucidate the mechanism of ENT1 regulation by KDM6A, we performed ChIP-seq analysis for H3K27me3 and H3K27ac in the sister cell lines MM-1 (KDM6A WT) and MM-6 (KDM6A KO). ChIP-seq for H3K27me3 showed no enrichment on the ENT1 locus, but we detected differential H3K27ac peaks in the promoter and a putative enhancer region of ENT1 in MM-1 compared to MM-6. These data suggest that increased ENT1 expression may function through direct or indirect effects of KDM6A on enhancer regions, independent of its H3K27 demethylase activity. In conclusion, our results show that mutations in KDM6A are associated with the outgrowth of drug-resistant clones and highlight KDM6A as a novel biomarker of drug resistance in AML. Disclosures Hiddemann: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffman-La Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Consultancy, Research Funding. Metzeler:Novartis: Consultancy; Celgene: Consultancy, Research Funding.

Vorinostat Impairs Cellular Viability, Differentiation, Redox Homeostasis and Gene Expression in BCR-ABL-Negative Myeloproliferative Neoplasms

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3222-3222
Author(s):  
Bruno A Cardoso ◽  
Helio Belo ◽  
Antonio Almeida
Keyword(s):  
Bone Marrow ◽  
Board Of Directors ◽  
Cell Lines ◽  
Myeloproliferative Neoplasms ◽  
Hdac Inhibitors ◽  
Growth Arrest ◽  
Dependent Manner ◽  
Advisory Committees ◽  
Expression Of Genes

Abstract Background: The classical BCR-ABL-negative myeloproliferative neoplasms (MPN) are characterized by increased proliferation of hematopoietic precursors in the bone marrow resulting in an elevated number of terminally differentiated cells. Despite the recent description of JAK2 activating mutations and other mutations, these do not completely explain the pathophysiology and clinical heterogeneity of MPN. Epigenetic modifications, particularly histone acetylation, play pivotal roles in the pathogenesis of several hematological malignancies, and treatment of such disorders with histone deacetylase inhibitors results cell death and proliferation arrest. Importantly, epigenetic agents have proven to be effective in several hematological malignancies. Aims: HDAC inhibition has demonstrated some efficacy in patients with MPN. In order to investigate the effects of HDAC inhibitors in MPN, we analyzed the impact of Vorinostat on the cellular biology of MPN cell lines and primary bone marrow samples. Material and Methods: MPN bone marrow samples were collected at diagnosis following informed consent in the course of routine clinical laboratory tests. Mononuclear cells were isolated by gradient separation were used for culture experiments and lysed for RNA extraction. RNA extracted from MPN primary samples was used to synthetize cDNA and the transcript levels of genes associated with Apoptosis, Proliferation, Epigenetic modifications and several Signaling pathways were analyzed by quantitative-PCR. MPN primary cells and MPN derived cell lines were incubated with Vorinostat and at different time points the cells were harvest, lysed for gene expression analysis and stained with different antibodies, Annexin-V/PI and DCF-DA to analyze cellular differentiation, apoptosis and Reactive Oxygen Species (ROS) respectively. Results: We performed a targeted-genome wide screen and compared the transcript levels of a defined set of genes between normal bone marrow and MPN primary samples. We identified 9 genes (BIRC3, TNFRSF9, DLL4, IL1B, CDKN1A, FOSL1, CREL, SERPINB9 and EGR1) whose expression increased for at least 4 fold and 2 genes (HIP1 and DTX1) whose expression decreased by at least 0.5 fold in MPN patients relative to normal bone marrow samples. Interestingly, incubation of Vorinostat in MPN cell lines at physiological concentrations increases the expression of such genes, and also the expression of genes associated with apoptosis and growth arrest while decreasing the expression of genes associated with proliferation, growth arrest and JAK-STAT signaling pathway. Regarding cellular physiology, Vorinostat induces apoptosis in MPN cultured cell lines in a time- and dose-dependent manner. Furthermore, incubation of primary MPN bone marrow samples with Vorinostat induced apoptosis, blocked differentiation and also diminished ROS levels in a dose dependent manner. These effects were most marked in the monocytic lineage, a population which expresses the highest levels of ROS. Vorinostat also reduced the levels of GPA and CD61, markers of erythroid and megakaryocytic differentiation, respectively. Summary/Conclusions: Here, we show that Vorinostat incubation impairs MPN cellular differentiation and reduces ROS and cellular viability, possibly through the down-regulation of genes associated with cellular proliferation, particularly the JAK-STAT target genes, and up-regulation of genes important for apoptosis and growth arrest. Interestingly, the genes that we identified to be up-regulated in MPN primary samples relative to normal controls, are further increased by Vorinostat treatment, suggesting that these could act as potential biomarkers for Vorinostat effectiveness in the MPN context. Furthermore, these results hold therapeutic promise as Vorinostat reduced differentiation markers associated with Polycythemia Vera and Essential Thrombocytosis. The observation that Vorinostat is particularly effective against the monocytic lineage is interesting in the context of the recently described role of bone marrow monocytes in the pathogenesis of Polycythemia Vera in mouse models. Our results point towards the potential role of Vorinostat (and possibly other HDAC inhibitors) in the treatment of MPN. This potential would require clinical trials to investigate its efficacy. Disclosures Almeida: Celgene: Consultancy; Novartis: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; Shire: Membership on an entity's Board of Directors or advisory committees; Bristol-Meyer Squibb: Membership on an entity's Board of Directors or advisory committees.

Epigenetic Targeting with EZH2 and HDAC Inhibitors Is Synergistic in EZH2 Deregulated Lymphomas

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 839-839 ◽  
Author(s):  
Jennifer Kimberly Lue ◽  
Sathyen A Prabhu ◽  
Yuxuan Liu ◽  
Owen A. O'Connor ◽  
Jennifer E Amengual
Keyword(s):  
T Cell ◽  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Single Agent ◽  
Hdac Inhibitors ◽  
Lymphoma Cell ◽  
Advisory Committees ◽  
Genetics Research ◽  
Transcriptional Inhibition

Abstract EZH2 is critical in a process known as the Germinal Center (GC) reaction during which B-cells undergo somatic hypermutation and isotype switching in order to develop a large antibody repertoire. EZH2 is a histone methyltransferase serving as the catalytic subunit of the Polycomb Repression Complex 2 (PRC2), which is responsible for tri-methylation of histone 3 lysine 27 (H3K27), a mark of transcriptional repression. EZH2 recruits HDAC1/2 and DNMTs through its cofactor EED to further inhibit transcription. Mutations in EZH2 are found in 7-12% of FL and 22% of GC-DLBCL. EZH2 overexpression secondary to MYC and miRNA dysfunction has also been described. EZH2 also plays a role in T-cell differentiation and has been found in various T-cell malignancies. Histone acetyltransferases (HAT), notably CBP and p300, have also been implicated in B- and T-cell lymphomas and are mutated/deleted in 39% of GC-DLBCL and 41% of FL. Given the presence of EZH2 and HAT dysregulation in lymphoma, we evaluated the potential synergy of EZH2 and HDAC inhibitors co-treatment. Single agent activity for GSK126, an EZH2 inhibitor, and romidepsin, a pan-HDAC inhibitor, was established in a panel of lymphoma cell lines (GC-DLBCL, Non-GC DLBCL, MCL and T-Cell lymphoma, n=21). Cell lines with known EZH2 dysregulation (GC-DLBCL and ATLL) were more sensitive to EZH2 inhibitors as exhibited by lower half maximal effective concentration (EC50) after 6 day exposure (EC50 0.01-16 µM). There was no association between HAT mutation/deletion and romidepsin sensitivity. A panel of lymphoma cell lines was treated for 72 hr with GSK126 and romidepsin using concentrations represented by their EC30-50 (0.5-4.0 µM), and EC20-40 (1.0-4.0 nM), respectively. Synergy was assessed by Excess over Bliss (EOB), where EOB > 10 represents synergy. Simultaneous exposure to GSK126 and romidepsin in GC-DLBCL cell lines demonstrated potent synergy as represented by EOB > 30. Synergy was also present in ATLL cell lines (EOB 28), which are known to have EZH2 dysregulation, as well as non-GC DLBCL cell lines (EOB 47). Although these cell lines do not have EZH2 mutations, some possess relative EZH2 over-expression compared to other lymphomas. Evaluation of drug schedule using GSK126 pretreatment prior to romidepsin exposure did not impact synergy. Compared to single agent activity, the combination of GSK126 (2 µM) and romidepsin (1-4 nM) led to a more pronounced decrease in H3K27 tri-, di-, and mono-methylation and increased acetylation in 4 GC-DLBCL cell lines (OCI-LY7, Pfeiffer, SU-DHL-6, SU-DHL-10) at 24 or 48 hrs. The impact of the combination on the function of the PRC2 complex was assessed via co-immunoprecipation in these cell lines. The combination demonstrated dissociation of the PRC2 complex (EZH2, SUZ12, EED, and RbAp46/48) as compared to single agent exposure. Treatment with the combination also induced dissociation of HDAC2 and DNMT3L. In addition, we observed decreased protein expression of PRC2 complex members and increased p21/CDKN1A, which was more notable in the combination treatment as compared to single agent. This may be due to the removal of HDACs from the p21 transcriptional start site through the disruption of the PRC2 complex and direct inhibition of HDACs, thus leading to increase expression of p21. The combination also led to decreased nuclear localization of EZH2 and its cofactors. Apoptosis was confirmed by caspase 3 and PARP cleavage, and was more potently cleaved after exposure to the combination. Based on the findingthat HDAC2 dissociated from PRC2 complex after treatment with GSK126 and romidepsin, a selective HDAC1/2 inhibitor, ACY-957 (Acetylon Pharmaceuticals), was combined with GSK126 which demonstrated potent synergy in 4 GC-DLBCL cell lines (EOB 37). This data suggests that concomitant inhibition of EZH2 and HDAC is highly synergistic and leads to the dissociation of PRC2 complex. By releasing transcriptional inhibition key tumor suppressors and cell cycle regulators may be re-expressed. Potency of this epigenetic combination may be predicted by gene expression signatures for which RNA-seq libraries are currently in production. Reversing transcriptional inhibition using a combination of EZH2 inhibitors and HDAC inhibitors may lead to a potent treatment option for lymphomas dependent upon EZH2 and HAT activity. Figure 1 Figure 1. Disclosures O'Connor: Seattle Genetics: Research Funding; Spectrum: Research Funding; Seattle Genetics: Research Funding; Spectrum: Research Funding; Mundipharma: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Research Funding; Mundipharma: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Research Funding; Bristol Myers Squibb: Research Funding; Bristol Myers Squibb: Research Funding; Celgene: Research Funding; Celgene: Research Funding. Amengual:Acetylon Pharmaceuticals: Research Funding; Bristol-Myers Squibb: Research Funding.

scholarly journals RON Kinase Is a Novel Therapeutic Target for Philadelphia-Negative Myeloproliferative Neoplasms

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1462-1462
Author(s):  
Lindsay Meg Gurska ◽  
Rachel Okabe ◽  
Meng Maxine Tong ◽  
Daniel Choi ◽  
Kristina Ames ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Board Of Directors ◽  
Research Funding ◽  
Myeloproliferative Neoplasms ◽  
Marrow Transplant ◽  
Jak Inhibitor ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Stat Signaling ◽  
Genetic Deletion

Abstract The Philadelphia-chromosome negative myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocytosis (ET), and primary myelofibrosis (PMF), are clonal hematopoietic stem cell disorders characterized by the proliferation of one or more myeloid lineage compartments. Activation of JAK/STAT signaling is a major driver of all Ph-negative MPNs. During disease progression, MPN patients experience increased pro-inflammatory cytokine secretion, leading to remodeling of the bone marrow microenvironment and subsequent fibrosis. The JAK inhibitor ruxolitinib is an approved targeted therapy for MPN patients and has shown promise in its ability to reduce splenomegaly and the cytokine storm observed in patients. However, JAK inhibitors alone are not sufficient to reduce bone marrow fibrosis or to eliminate the JAK2-mutated clone. Furthermore, JAK inhibitor persistence, or reactivation of JAK/STAT signaling upon chronic JAK inhibitor treatment, has been observed in both MPN mouse models and MPN patients. Therefore, there is an urgent need for new treatment options in MPN. The tyrosine kinase RON, a member of the MET kinase family, has well-characterized roles in erythroblast proliferation and pro-inflammatory cytokine production. RON can be phosphorylated by JAK2 to stimulate erythroblast proliferation. However, the role of RON in MPN pathogenesis is unknown. We found that the ALK/MET/RON/ROS1 inhibitor crizotinib inhibited colony formation by MPN patient CD34+ cells, regardless of their disease subtype, mutation status, or JAK2 inhibitor treatment history (Figure 1A). To determine whether this is due to inhibition of the JAK/STAT signaling pathway, we performed phospho-flow cytometry of STAT3 and STAT5 in myelofibrosis patient erythroblasts treated with crizotinib ex vivo as well as Western blot analysis in the JAK2-mutated cell lines SET2 and HEL. We found that crizotinib inhibits the phosphorylation of JAK2, STAT3, and STAT5 (Figure 1B). Since crizotinib has not been reported to directly inhibit JAK2, we asked whether these effects of crizotinib in MPN cells could be explained by RON inhibition. Consistent with this hypothesis, we observed that shRNA knockdown of multiple RON isoforms also decreases the phosphorylation of JAK2, STAT5, and STAT3 in HEL cells (Figure 1C-D). To determine whether crizotinib can alter the MPN disease course in vivo, we tested crizotinib by oral gavage in the MPLW515L bone marrow transplant murine model of myelofibrosis at 100mg/kg daily for 2 weeks. We showed that crizotinib decreased the disease burden of MPL-W515L mice, as evidenced by decreased spleen and liver weights (Figure 1E). To determine the effects of RON genetic deletion on MPN pathogenesis, we tested whether genetic deletion of Stk (mouse gene for RON) impairs disease progression in the JAK2V617F bone marrow transplant MPN model by transplanting Stk-/- c-Kit+ bone marrow cells transduced with the JAK2V617F-GFP retrovirus into lethally irradiated recipients. We observed a significant delay in disease onset in Stk-/- transplant recipients compared to WT controls (Figure 1F). However, we found that Stk-/- mice have normal numbers of hematopoietic stem and progenitor cells, and normal bone marrow myeloid colony forming capacity, suggesting that RON is a safe therapeutic target. To determine whether RON plays a role in the JAK inhibitor persistence phenotype, we generated persistent cells by treating SET2 cells with increasing doses of ruxolitinib over 8 weeks, and confirmed persistent proliferation and JAK/STAT activation. Interestingly, we found that RON phosphorylation is enhanced in JAK inhibitor persistent cells, and that dual inhibition of RON and JAK2 overcomes JAK inhibitor persistence in SET2 cells (Figure 1G-H), suggesting that RON may potentiate the JAK2 persistence phenotype in response to ruxolitinib. Importantly, we showed by immunoprecipitation that phospho-RON and phospho-JAK2 physically interact in JAK inhibitor persistent SET2 cells, and that this interaction is disrupted by crizotinib (Figure 1I). In summary, our data demonstrate that RON kinase is a novel mediator of JAK/STAT signaling in MPNs, and that it plays a particularly important role in JAK inhibitor persistence. Our work suggests that therapeutic strategies to inhibit RON, such as crizotinib, should be investigated in MPN patients. Figure 1 Figure 1. Disclosures Halmos: Guardant Health: Membership on an entity's Board of Directors or advisory committees; Apollomics: Membership on an entity's Board of Directors or advisory committees; TPT: Membership on an entity's Board of Directors or advisory committees; Eli-Lilly: Research Funding; Advaxis: Research Funding; Blueprint: Research Funding; Elevation: Research Funding; Mirati: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer-Ingelheim: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra-Zeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding. Gritsman: iOnctura: Research Funding.

scholarly journals Bitter Taste Receptors System Is Expressed and Functional in Both HSCs and Leukemic Cells

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 2560-2560
Author(s):  
Valentina Salvestrini ◽  
Valentina Pensato ◽  
Marilena Ciciarello ◽  
Giorgia Simonetti ◽  
Dorian Forte ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Bitter Taste ◽  
Leukemic Cells ◽  
Leukemia Cells ◽  
High Dose ◽  
Taste Receptors ◽  
Advisory Committees ◽  
Hematopoietic Stem

Abstract Acute Myeloid Leukemia (AML) is a clonal disease sprouting from a rare population of leukemic stem cells. Over the past years, increasing interest is gaining the contribution that cell-extrinsic factors have in AML generation and maintenance. In this context, the ability of leukemia cells to detect changes in the microenvironment is important in responsiveness to environmental fluctuations. Bitter taste receptors (T2Rs) are typical G-protein coupled receptors and are normally found on the surface of the tongue. Recent studies showed that T2Rs are widely expressed in various parts of human anatomy and have been shown to be involved in physiology of respiratory system, gastrointestinal tract and endocrine system. thus suggesting a wider function in "sensing microenvironment". We recently reported that AML cell lines OCI-AML3, THP-1, and AML primary cells expressed fully functional T2Rs subtypes. Gene expression profile analysis showed that after T2Rs activation, leukemic cell lines underwent down-regulation of genes involved in positive regulation of cell proliferation, migration, and cell-cycle. Whereas genes involved in cell adhesion and DNA repair were up-regulated. Functional assays supported these results (Blood 2017 130:3949). In the present work, we further investigated the role of T2Rs in BM microenvironment by extending the analysis to AML primary samples and to normal hematopoietic stem cells (HSCs). Similarly to AML cell lines, T2Rs activation with high dose of agonist induced a reduction of cell viability associated to apoptosis induction, while non-toxic doses reduced cell migration and clonogenic capacity. In addition, T2Rs stimulation with agonist makes AML cell lines more prone to oxidative and metabolic stress. Leukemia cells displayed a quiescent phenotype in response to T2Rs activation suggesting that mitochondrial activity is significantly limited by T2Rs agonist treatment. Since no data are available on the presence and the function of T2Rs on normal hematopoietic stem cell counterpart, we characterized T2Rs expression on CD34+ cell isolated from healthy donor. CD34+ cells express several T2Rs subtype without significant differences compare to AML cells. Their activation with high dose of agonist reduced HSCs viability inducing apoptosis, while non-cytotoxic doses reduced clonogenic capacity and promoted migration. Given the effect of T2Rs activation on crucial AML cell function, we tested the therapeutical potential of T2R agonist with and without conventional chemioterapic agent. Interestingly we observed that T2Rs agonist have a synergistic effect with cytarabine, reducing leukemia cell viability when combined with ARA-C compared to their use as single compound. The combination allowed to reach a high toxicity using lower doses of chemotherapic agent. Overall our results indicate that T2Rs receptor system is expressed and functional in both leukemic cells and HSCs. In particular, in AML cells T2Rs activation is associated with quiescence induction and prevention of migration. T2Rs stimulation modulates HSCs function but their role need to be further deepen. These data may suggest a role for microenvironment "bitter" molecules in regulating normal and leukemic hematopoiesis. Disclosures Cavo: AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees.

scholarly journals Dysfunctional HDAC8 Impacts Genomic Integrity and Is a Novel Therapeutic Target in Multiple Myeloma

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1610-1610
Author(s):  
Zuzana Chyra ◽  
Srikanth Talluri ◽  
Rao Prabhala ◽  
Mehmet K. Samur ◽  
Anil Aktas-Samur ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Growth ◽  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Hdac Inhibitors ◽  
Dependent Manner ◽  
Dna Breaks ◽  
Advisory Committees

Abstract The histone modifications and associated changes in chromatin structure and function have emerged as important epigenetic mechanisms impacting gene expression and have significant translational relevance in cancers, including multiple myeloma (MM). Epigenetic intervention with histone deacetylases (HDACs) inhibitors is emerging as a promising therapeutic strategy in combination with current anti-myeloma agents. Although pan-HDAC inhibitors have been shown to be effective both in preclinical and clinical setting, they seem to be associated with toxicity. It is, therefore, extremely important to understand the biological and molecular roles of individual HDACs to then selectively target them to limit toxicities observed with pan-HDAC inhibitors. Based on our observation that elevated HDAC8 expression correlates with poor overall survival in MM patients in three different datasets including one publicly available dataset (GSE39754), we evaluated its functional role in MM. HDAC8, a member of class I HDAC isoenzymes, is responsible for the deacetylation of lysine residues on the N-terminal part of the core histones as well as non-histone proteins. We performed genetic modulation of HDAC8 by loss-of-function studies, using shRNA as well as siRNAs targeting HDAC8. Downregulation of HDAC8 in 3 different MM cell lines caused MM cell growth inhibition in a time-dependent manner which was associated with induction of cell apoptosis. Consistently, treatment with a selective and potent HDAC8 inhibitor (OJI-1) caused a significant inhibition of MM cell growth in a panel of 20 MM cell lines (IC50 = 80 nM) in a time- and dose-dependent manner, while having a minimal impact on six PBMC samples from healthy donors both in resting and activated state (IC50 = 150 nM). The mechanism of cell death was apoptosis as demonstrated by annexin-labeling. Importantly, both the HDAC8 knockdown and OJI-1 treatment inhibited DNA breaks as evidenced from γH2AX expression or a single cell gel electrophoresis method to visualize and quantitate DNA breaks. HDAC8 inhibition also caused inhibition of RAD51 foci and HR activity, as measured by strand-exchange assay. Interestingly, non-homologous end joining in MM cells was not impacted by these treatments. Consistent with these data, the overexpression of HDAC8 in MM as well as in normal cells increased DNA breaks and HR activity. Furthermore, the inhibition of HDAC8 (by knockdown and OJI-1) inhibited, whereas its overexpression increased genomic instability, as assessed by micronucleus assay, in surviving MM cells. We also demonstrate that HDAC8 interacts with RAD51 and impacts its acetylation. The treatment of MM cells with HDAC8 inhibitor (OJI-1) increased RAD51 acetylation. Next, we examined the in vivo efficacy of the HDAC8 conditional knockdown in a human xenograft mouse model, using H929 cells injected subcutaneously in SCID mice. HDAC8 knockdown not only caused a significant reduction in tumor growth but also increased survival (p=0.0016) compared to mice injected with control cells. Evaluation of tumors from these mice confirmed in vivo inhibition of DNA breaks and HR activity, and induction of apoptosis following HDAC8-knockdown. HDAC8 inhibitor OJI-1 also synergistically increased the cytotoxicity of existing MM drugs including dexamethasone, bortezomib and lenalidomide. In conclusion, our results demonstrate that elevated HDAC8 in MM cells is involved in inhibition of apoptosis but also contributes to increased DNA breaks and dysregulation of homologous recombination and genome stability. Therefore, HDAC8 is a novel target for therapeutic application in MM. Selective and potent HDAC8 inhibitor OJI-1 has shown a favorable therapeutic index with synergistic effect in combination with existing MM drugs. Disclosures Hajek: Pharma MAR: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Honoraria, Research Funding. Munshi: Janssen: Consultancy; Bristol-Myers Squibb: Consultancy; Amgen: Consultancy; Takeda: Consultancy; Celgene: Consultancy; Karyopharm: Consultancy; Abbvie: Consultancy; Adaptive Biotechnology: Consultancy; Oncopep: Consultancy, Current equity holder in publicly-traded company, Other: scientific founder, Patents & Royalties; Novartis: Consultancy; Pfizer: Consultancy; Legend: Consultancy.

scholarly journals Development of Cirmtuzumab Antibody-Drug Conjugates (ADCs) Targeting Receptor Tyrosine Kinase-like Orphan Receptor 1 (ROR1)

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1862-1862 ◽  
Author(s):  
Yousaf A. Mian ◽  
George F. Widhopf II ◽  
Thanh-Trang Vo ◽  
Katti Jessen ◽  
Laura Z. Rassenti ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Cell Lines ◽  
Half Life ◽  
Research Funding ◽  
Leukemia Cell ◽  
Volume Distribution ◽  
Advisory Committees ◽  
High Affinity

Abstract ROR1 is an onco-embryonic surface antigen expressed on chronic lymphocytic leukemia (CLL) and a variety of other cancers, but not on most normal adult tissues. We generated a humanized IgG1 monoclonal antibody (mAb) cirmtuzumab (formerly UC-961) that binds with high affinity to a specific extracellular epitope of human ROR1 and that can block Wnt5a-induced ROR1 signaling (Yu, J et al, J Clin Invest126:585, 2016; Yu, J et al, Leukemia31:1333, 2017). Preclinical studies found that cirmtuzumab did not react with normal post-partem cells and had a pharmacokinetic (PK) volume distribution in primates consistent with a lack of off-target binding to normal tissues. We evaluated cirmtuzumab in a phase I clinical trial involving patients with relapsed-refractory CLL (Choi MY, et al, Cell Stem Cell22:951, 2018); the drug was well-tolerated at doses ≤20 mg/kg (highest dose tested) without dose-limiting toxicity. PK studies showed cirmtuzumab had a half-life of 32.4 days with no evidence for development of neutralizing antibodies or off-target sequestration of infused antibody. Furthermore, cirmtuzumab effected partial down-modulation of leukemia-cell ROR1 in patients treated with doses ≥2 mg/kg. In vitro confocal microscopy studies showed that this down-modulation was caused by internalization of cirmtuzumab-ROR1 complexes into lysosomal compartments and concomitant steady-state re-expression of nascent surface ROR1. Because of its high specificity, in vivo stability, long serum half-life, and potential capacity to concentrate conjugated drugs into lysosomal compartments, cirmtuzumab appeared ideally suited to serve as the targeting moiety in anti-ROR1 ADCs. We therefore examined cirmtuzumab-based ADCs in collaboration with VelosBio Inc., evaluating multiple linker/payload chemistries, both as single agents and in combinations. We selected for further testing cirmtuzumab-ADC-7, a cirmtuzumab-linker-monomethyl auristatin E (MMAE) ADC that preserves the high-affinity binding specificity of cirmtuzumab and allows for ROR1-targeted intracellular release of MMAE. We found cirmtuzumab-ADC-7 was selectively cytotoxic for ROR1+ CLL and mantle-cell lymphoma (MCL) cell lines at nM concentrations in vitro. Moreover, cirmtuzumab-ADC-7 caused dramatic and sustained in vivo clearance of adoptively-transferred ROR1+ leukemia cells generated from ROR1xTCL1 transgenic mice (Widhopf G, et al, PNAS111:793, 2014), ROR1+ MCL-xenografts, or ROR1+ cancer patient-derived xenografts (PDX). Further, treatment caused dose-dependent and statistically significant decreases in total cancer burden with complete regressions of tumor in multiple animals; no effect on tumor-clearance was observed in mice treated with a control MMAE-ADC of irrelevant specificity. Recently we identified that miR-15a/16-1, which commonly are deleted/downregulated in CLL, target both BCL2 and ROR1, thereby accounting in part for the direct relationship we observed between the levels of BCL2 and levels of surface ROR1 expressed by CLL of different patients (Rassenti, LZ, et al,PNAS114:10731, 2017). Because high level expression of BCL2/ROR1 may mitigate the cytotoxic activity of the BCL2-antagonist venetoclax, but potentially enhance the cytotoxicity of cirmtuzumab-ADC-7, we treated ROR1+ leukemia/lymphoma cell lines with venetoclax and/or cirmtuzumab-ADC-7. Chou-Talalay combination indices were <0.5 in all ROR1+ cell lines tested, indicating strong antitumor synergy with these two agents. Collectively these data support the rationale for clinical development of a cirmtuzumab-based ADC for treatment of patients with ROR1+ malignancies. Disclosures Vo: VelosBio: Employment. Jessen:VelosBio: Employment. Kipps:Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Verastem: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; Verastem: Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Honoraria, Research Funding; Genentech Inc: Consultancy, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees.

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