Subunit Of Polycomb Repressive Complex Research Articles

Easy or Not-The Advances of EZH2 in Regulating T Cell Development, Differentiation, and Activation in Antitumor Immunity.

Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of polycomb repressive complex 2 (PRC2), which regulates downstream gene expression by trimethylation of lysine 27 in histone H3 (H3K27me3). EZH2 mutations or overexpressions are associated with many types of cancer. As inhibition of EZH2 activity could upregulate the expression of tumor suppressor genes, EZH2 has recently become an interesting therapeutic target for cancer therapy. Moreover, accumulating evidence has shown that EZH2 may contribute to the regulation of immune cells, especially T cells. EZH2 regulates T cell development, differentiation, and function, suggesting that EZH2 also regulates immune homeostasis in addition to tumor suppressor genes. Moreover, EZH2 can regulate T cell fate by targeting non-T cell factors such as metabolism, cytokines, and myeloid-derived suppressor cells. The role of EZH2 in this process has not been fully addressed. This review discusses up-to-date research on EZH2-mediated regulation of immunological function and the progress of immunological therapeutic strategies based on this regulation.

Discovery of IHMT-EZH2-115 as a Potent and Selective Enhancer of Zeste Homolog 2 (EZH2) Inhibitor for the Treatment of B-Cell Lymphomas.

The enhancer of zeste homologue 2 (EZH2) is the catalytic subunit of polycomb repressive complex 2 that catalyzes methylation of histone H3 lysine 27 (H3K27). Overexpression or mutation of EZH2 has been identified in hematologic malignancies and solid tumors. Based on the structure of EPZ6438 (1) and the binding model with PRC2, we designed a series of analogues aiming to improve the activities of EZH2 mutants. Structure-activity relationship (SAR) exploration at both enzymatic and cellular levels led to the discovery of inhibitor 29. In the biochemical assay, 29 inhibited EZH2 (IC50 = 26.1 nM) with high selectivity over other histone methyltransferases. It was also potent against EZH2 mutants (EZH2 Y641F, IC50 = 72.3 nM). Furthermore, it showed no apparent inhibitory activity against the human ether-á-go-go related gene (hERG) (IC50 > 30 μM). In vivo, 29 exhibited favorable pharmacokinetic properties for oral administration and showed better efficacy than 1 in both Pfeiffer and Karpas-422 cell-mediated xenograft mouse models, indicating that it might be a new potential therapeutic candidate for EZH2 mutant cancers.

A PRC1-RNF2 knockout punch for cancer.

Shedding light on epigenetic mechanisms controlling anti-tumor immune responses, a new study shows that the tumor-intrinsic ring finger protein 2 (RNF2), the catalytic subunit of Polycomb repressor complex 1 (PRC1), acts as a negative regulator of a collaborative NK and CD4+ T cell anti-tumor immune response against breast cancer.

PALI1 facilitates DNA and nucleosome binding by PRC2 and triggers an allosteric activation of catalysis

The polycomb repressive complex 2 (PRC2) is a histone methyltransferase that maintains cell identities. JARID2 is the only accessory subunit of PRC2 that known to trigger an allosteric activation of methyltransferase. Yet, this mechanism cannot be generalised to all PRC2 variants as, in vertebrates, JARID2 is mutually exclusive with most of the accessory subunits of PRC2. Here we provide functional and structural evidence that the vertebrate-specific PRC2 accessory subunit PALI1 emerged through a convergent evolution to mimic JARID2 at the molecular level. Mechanistically, PRC2 methylates PALI1 K1241, which then binds to the PRC2-regulatory subunit EED to allosterically activate PRC2. PALI1 K1241 is methylated in mouse and human cell lines and is essential for PALI1-induced allosteric activation of PRC2. High-resolution crystal structures revealed that PALI1 mimics the regulatory interactions formed between JARID2 and EED. Independently, PALI1 also facilitates DNA and nucleosome binding by PRC2. In acute myelogenous leukemia cells, overexpression of PALI1 leads to cell differentiation, with the phenotype altered by a separation-of-function PALI1 mutation, defective in allosteric activation and active in DNA binding. Collectively, we show that PALI1 facilitates catalysis and substrate binding by PRC2 and provide evidence that subunit-induced allosteric activation is a general property of holo-PRC2 complexes.

Abstract CT176: Phase 2 study of tazemetostat in Japanese patients with relapsed or refractory EZH2 mutation-positive B-cell Non-Hodgkin's Lymphoma

Abstract Background: Tazemetostat is a selective, reversible, small-molecule inhibitor of enhancer of zest homolog 2 (EZH2), a histone methyltransferase. EZH2 is the catalytic subunit of polycomb repressive complex 2, which methylates lysine 27 on histone 3 (H3K27). Recurrent gain-of-function alterations in EZH2 occur in approximately 30% of germinal center B-cell like diffuse large B-cell lymphoma (GCB-DLBCL) and 27% of follicular lymphoma (FL). The aim of this multicenter, open-label, Phase 2 study was to assess the efficacy and safety of tazemetostat in Japanese patients with relapsed or refractory B-cell Non-Hodgkin's Lymphoma (NHL) harboring the EZH2 mutation. Methods: Patients with histologically diagnosed FL (cohort 1) or DLBCL (cohort 2) were screened centrally for EZH2 mutation using the cobas EZH2 Mutation Test. Tazemetostat (800 mg BID) was administered orally for 28 days/cycle until disease progression, occurrence of unacceptable toxicity, or withdrawal of consent. The primary endpoint was the objective response rate (ORR) based on IWG-2007 by independent imaging review and safety was evaluated as the secondary endpoint. Results: Among the 20 eligible patients, 17 were enrolled in cohort 1, and 3 were enrolled in cohort 2. In cohort 1, the median number of prior chemotherapy was 2 (range 1-4) and the ORR was 76.5% , including 6 patients (35.3%) achieving a complete response and 7 patients (41.2%) achieving a partial response (PR) as of the data cutoff. The ORR in subjects who received prior treatment with bendamustine, rituximab, and CHOP was 87.5%, 76.9%, and 76.9%, respectively. All 3 patients in cohort 2 (100%) achieved PR. In cohort 1, 3 of the 17 subjects (17.6%) had progression-free survival (PFS) events. The median PFS was not reached. Estimated PFS rates at 12 and 15 months based on the Kaplan-Meier analysis were 94.1% and 73.2%, respectively. The median duration of response (DOR) was not reached, and the DOR rate at 9 and 12 months was 100% and 80.0%, respectively. The median time to response was 3.6 months. The most common grade-3 treatment emergent adverse event (TEAE) was lymphopenia (2 patients, 10.0%). Grade-4 TEAEs included hypertriglyceridemia and pneumonia aspiration (1 patient each, 5.0%). TEAEs leading to study drug discontinuation were reported by 4 of 20 (20.0%) patients, including fatigue (2 patients, 10.0%), atypical pneumonia, traumatic intracranial haemorrhage, non-small cell lung cancer, muscle spasticity, and dysgeusia (1 patient each, 5.0%), indicating that the safety profile was acceptable and manageable. Conclusion: Tazemetostat at a dose of 800 mg BID showed encouraging efficacy in patients with relapsed or refractory EZH2 mutation-positive FL with an acceptable safety profile in the overall population. Thus, tazemetostat may be a potential option for the treatment of relapsed or refractory EZH2 mutation-positive FL. Citation Format: Shinya Rai, Kiyoshi Ando, Akifumi Takaori-Kondo, Hirohiko Shibayama, Takanori Teshima, Junya Kuroda, Koji Kato, Yoshitaka Imaizumi, Kisato Nosaka, Rika Sakai, Tadashi Nakanishi, Seiichiro Hojo, Koji Izutsu. Phase 2 study of tazemetostat in Japanese patients with relapsed or refractory EZH2 mutation-positive B-cell Non-Hodgkin's Lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT176.

Abstract 1142: A novel and potent EZH1/2 dual inhibitor, HM97662, demonstrates antitumor activity in malignant tumors

Abstract Either enhancer of zeste homolog 2 (EZH2) or its homolog EZH1, the enzymatic core subunit of polycomb repressive complex 2 (PRC2), acts an essential role for the maintenance of transcriptional repression by the methylation of histone H3 lysine 27 (H3K27). EZH2 gain-of-function (GOF) mutations (e.g. Y641, A677, and A687) or wild-type activation cause an increased activity leading to hyperinduce trimethylation of H3K27 (H3K27me3). Meanwhile, loss-of-function (LOF) mutation of major components (e.g. ARID1A, PBRM1, INI1) in chromatin remodeling complex, SWItch/Sucrose Non-Fermentable (SWI/SNF), results in a loss of its ability to oppose PRC2 and subsequently activation of EZH2. Accordingly, the dysfunctions of EZH2 or the alterations of regulatory SWI/SNF complex proteins have been reported to be associated with the development and progression of a variety of malignant tumors. Although PRC2 is suppressed by EZH2 inhibition, the activity of EZH1 is complementarily increased to replace the role of EZH2. Consequently, dual inhibition of EZH1 and EZH2 could be more effective than EZH2 inhibition alone in blocking PRC2 function as an anti-cancer therapy. Thus, we have developed a novel EZH1/2 dual inhibitor, HM97662, which simultaneously inhibited the methyltransferase activity of wild-type EZH1 as well as wild-type and GOF mutant EZH2 at nanomolar concentrations. Herein, we presented that HM97662, having enhanced EZH1 inhibitory activity compared to EZH2 inhibitors currently approved or in clinical development, potently and dose-dependently decreased global H3K27me3 in cancer cells. HM97662 showed broader and stronger anti-proliferative activities against various hematological cancer cell lines with EZH2 activating mutations as well as solid tumor cell lines with negatively mutated components of regulatory protein complexes. At this time, it was confirmed in the MCL cell line that HM97662, unlike the EZH2 selective inhibitor, does not cause the elevation of EZH1. HM97662 was observed to effectively modulate cell cycle arrest and induce apoptotic markers in a dose-dependent manner, as well as decrease intracellular H3K27me3, a pharmacodynamic marker, even at low concentration. As a result, HM97662 inhibited tumor growth more effectively than known EZH2 selective inhibitor without abnormal clinical signs at once daily dose in an EZH2 GOF mutant lymphoma cell xenograft mice model as well as in a bladder cancer cell xenograft mice model harboring a genetically mutated regulatory SWI/SNF complex protein (e.g. ARID1A). Taken together, the present studies demonstrated that HM97662 is a novel and potent EZH1/2 dual inhibitor and has the promising potential for the treatment of patients with several types of cancers. Clinical trials to prove the effectiveness of HM97662 identified in preclinical studies need to be carried out immediately. Citation Format: Seung Hyun Jung, DongJin Hong, Jiyoung Hwang, Somin Park, Jooyun Byun, Miyoung Lee, Kyounghwa Koo, Gunwoo Lee, Yu-Yon Kim, Yesol Bak, Young Gil Ahn, YoungHoon Kim, Kwee Hyun Suh. A novel and potent EZH1/2 dual inhibitor, HM97662, demonstrates antitumor activity in malignant tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1142.

Abstract 2126: Therapeutic potential of CPI-0209

Abstract Second-generation EZH2 inhibitor CPI-0209 has therapeutic potential for androgen receptor-dependent prostate cancer Rentian Wu, Feng Zhao, Patricia J. Keller, Jennifer A. Mertz, John P. McGrath, Barbara Bryant, Andrew R. Conery, Kaiming Sun, Jing Wang, and Patrick Trojer Post-translational modification of histones plays critical roles in epigenetic regulation of gene expression. Enhancer of Zeste Homolog 2 (EZH2), a subunit of Polycomb Repressive Complex 2 (PRC2), catalyzes trimethylation of histone H3 on lysine 27 (H3K27me3). Chromatin methylation by EHZ2 promotes chromatin architectural changes and silencing of gene expression. EZH2-mediated gene silencing was shown to contribute to tumor initiation and progression. Amplification and overexpression of EZH2 along with down regulation of its target genes correlate with treatment resistance and poor prognosis in various tumor types including metastatic castration resistant prostate cancer (mCRPC). While most mCRPC patients are initially responsive to agents targeting the androgen receptor (AR) signaling pathway, tumors eventually develop resistance and progress. Other than EZH2 overexpression, mechanisms of resistance involve AR alterations, including AR amplification, alteration of AR splice variants which constitutively activate ARS, and AR mutations that affect native ligand-binding specificity. CPI-0209 is an orally bioavailable and selective EZH2 and EZH1 inhibitor with highly enhanced potency and extended residence time compared to first-generation EZH2 inhibitors. CPI-0209 is currently being clinically developed as monotherapy and in combination with other cancer therapeutic agents [NCT04104776]. Here we demonstrated that AR-dependent prostate cancer cell lines including LNCaP, 22Rv1 and VCaP were sensitive to CPI-0209 treatment, while AR-independent cell lines like PC3 and DU145 were insensitive to CPI-0209. Sensitivity to CPI-0209 were also observed in AR-dependent cell line-derived xenografts (CDX) and patient-derived xenografts (PDX) models. In AR-dependent cells, CPI-0209 synergized with enzalutamide and overcame the anti-androgens resistance induced by AR alterations. In prostate cancer CDX and PDX models, the combination treatment of CPI-0209 and enzalutamide showed greater tumor growth inhibition compared to enzalutamide monotherapy. Transcriptomic analysis revealed that CPI-0209 treatment modulated both AR-related and AR-independent pathways, which reveals a potential mechanism to explain the synergy of CPI-0209 and AR inhibitors. Thus, our results indicate that CPI-0209 may have the potential to be effective for AR-dependent mCRPC that are resistant to current AR inhibitors, supporting potential clinical development in mCRPC. Keywords: EZH2, prostate cancer, epigenetics, resistant Citation Format: Rentian Wu, Feng Zhao, Patricia J. Keller, Jennifer A. Mertz, John P. McGrath, Barbara Bryant, Andrew R. Conery, Kaiming Sun, Jing Wang, Patrick Trojer. Therapeutic potential of CPI-0209 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2126.

Abstract 2132: Ezh2-Y641F mutation interacts with Stat3 to regulate the melanoma tumor immune response via disruption of IFN signaling

Abstract Cancer genetic sequencing studies have identified systematic alterations of epigenetic and chromatin modifiers in most cancers, consistent with the fact that chromatin modifiers, such as the Polycomb Repressive Complex 2 (PRC2), regulate the expression of tumor suppressors. In melanoma, 10% of patients exhibit amplifications or point mutations in EZH2, the enzymatic subunit of PRC2; however, the oncogenic mechanisms of EZH2 mutations in melanoma remain elusive. Previously, we observed that expression of Ezh2-Y641F in melanoma cells resulted in upregulation of IFN-related genes. We thus sought to better understand this mutation and the consequences of IFN signaling changes on tumor growth and the tumor immune response. We discovered that Ezh2-Y641F directly interacts with and methylates Stat3, a known regulator of interferon signaling. To understand the effects of this interaction, we performed ChIP-seq for Ezh2 and Stat3 in melanoma cells and found that the binding profiles of Stat3 and Ezh2 are greatly changed in Ezh2-Y641F cells. Furthermore, Ezh2 and Stat3 binding sites co-localized at several genomic loci in Ezh2-Y641F cells, including a region that regulates Ezh2. Knockdown of Stat3 in melanoma cells decreased Ezh2 expression and partially reduced expression of the IFN-related genes that were initially upregulated by Ezh2-Y641F. Analysis of the tumor-infiltrating immune cells by flow cytometry revealed increased CD8+ T cells and decreased myeloid cells in Ezh2-Y641F melanomas, consistent with a more favorable immune response, although tumor growth was unchanged. Genetic inhibition of Stat3 expression via shRNA rescued this phenotype. Our data suggest a novel interaction between the PRC2 complex and Stat3 in melanoma, which has significant physiological consequences on the tumor immune response. Molecular and genomic analysis suggest that Ezh2 and Stat3 together regulate gene expression, including Ezh2 itself. Overall, these data highlight the significant role of chromatin regulators on the tumor immune response. Citation Format: Sarah M. Zimmerman, Samantha Nixon, George P. Souroullas. Ezh2-Y641F mutation interacts with Stat3 to regulate the melanoma tumor immune response via disruption of IFN signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2132.

First-in-Human Study of the EZH1/2 Dual Inhibitor DS-3201b in Patients with Relapsed or Refractory Non-Hodgkin Lymphomas — Preliminary Results

First-in-Human Study of the EZH1/2 Dual Inhibitor DS-3201b in Patients with Relapsed or Refractory Non-Hodgkin Lymphomas — Preliminary Results

Population Pharmacokinetic and Exposure-Response Modeling for the EZH1/2 Dual Inhibitor DS-3201b in Patients with Non-Hodgkin Lymphomas

▪Introduction: Epigenetic regulators are an emerging new target class for cancer therapy. Enhancer of zeste homolog 1 (EZH1) and EZH2 are alternative subunits of polycomb repressive complex 2 (PRC2), and catalyze tri-methylation of the 27th lysine residue of histone H3 (H3K27). The tri-methylation of H3K27 (H3K27me3) plays an important role in the repression of genes associated with tumor suppression and cell differentiation. DS-3201b is a dual inhibitor of EZH1/2 with activity against hematological cancer cell lines that include acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), diffuse large B-cell lymphoma (DLBCL), and adult T-cell leukemia-lymphoma (ATL). The first-in-human (FIH) study (NCT02732275) is on-going to assess safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD) and potential anti-tumor activity in patients with relapsed or refractory non-Hodgkin lymphoma (NHL), including ATL. This preliminary analysis was aimed to develop a population PK model, to explore the exposure-response (E-R) relationships for key safety and PD endpoints, and to find the optimal dose and schedule for DS-3201b.Methods: As of August 2, 2017, clinical data that include plasma levels of DS-3201a (a free form of DS-3201b) and platelet counts were collected from 15 patients with NHL who were participated in the FIH study. They received DS-3201b oral once-daily dosing ranging from 150 mg to 300 mg in 28-day cycles. Population PK analysis for DS-3201a in plasma was carried out and the potential influence of patient characteristics on the PK of DS-3201a was investigated in a covariate analysis. The PK/PD model for platelet counts was developed using a semi-mechanistic model which consists of compartments that imitate platelet proliferation, maturation, circulation, and a feedback on proliferation. Preliminary E-R analyses were also performed for PD biomarker.Results: A 2-compartment PK model with first order elimination and absorption lag-time best characterized the plasma concentration-time profile of DS-3201a. Serum albumin was a significant covariate for total clearance. In the FIH study, platelet counts decreased to a nadir during the first treatment cycle and it returned to baseline without drug interruption in most patients who received 150 mg or 200 mg doses, whereas all patients who received 300 mg required dose interruption. The PK/PD model with drug effect on platelet proliferation and feedback compartments aptly described the time-course of platelet counts. Model-based simulations showed that up-titration schedule based on each patient's platelet count after cycle 1 treatment could allow administration of higher DS-3201b doses to a subset of patients with low risk of grade ≥3 thrombocytopenia. The results of E-R relationship for the inhibition of H3K27me3 in surrogate tissues will also be presented.Conclusion: We developed preliminary population PK and E-R models for DS-3201b in patients with relapsed or refractory NHL. Model-based simulations suggested that up-titration approach can be effective for DS-3201b to ensure continuity of treatment benefit while minimizing dose-dependent thrombocytopenia. DisclosuresAtsumi:Daiichi Sankyo Co., Ltd.: Employment. Yoshiba:DaiichiSankyo Co., Ltd: Employment. Maruyama:Dai-ichi Sankyo, Chugai, Kyowa Hakko Kirin, Ono, Celgene, Janssen, GSK, Eisai, Mundipharma, Takeda, AbbVie, MSD, Sanofi, Pfizer, Otsuka, Novartis, Solasia, Zenyaku: Research Funding; Chugai, Kyowa Hakko Kirin, Ono, Celgene, Janssen, Eisai, Mundipharma, Takeda: Honoraria. Tobinai:HUYA Bioscience: Honoraria; Janssen: Honoraria, Research Funding; AbbVie: Research Funding; Ono Pharmaceutical: Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Zenyaku Kogyo: Honoraria; Chugai: Honoraria, Research Funding; Eisai: Honoraria, Research Funding; Servier: Research Funding; Daiichi Sankyo Co., Ltd: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; GlaxoSmithKline: Research Funding; Kyowa Hakko Kirin: Honoraria, Research Funding. Ishida:Kyowa Hakko Kirin Co., Ltd. Celgene K.K. Bayer Pharma AG: Honoraria, Research Funding. Ishitsuka:Celgene Kyowa Hakko Kirin Bristol-Myers Squibb Chugai Pharmaceutical Takeda Pharmaceutical mundiharma Taiho Daiichi Sankyo Janssen Novartis Pfizer Astellas sanofi Genzyme Alexion Sumitomo Dainippon Eisai Mochida Shire Otsuka Ono Teijin: Honoraria, Research Funding. Tsukasaki:Kyowa-Kirin: Honoraria; Chugai/Roche: Honoraria; DaiichiSankyo: Consultancy; Celgene: Honoraria, Research Funding; Mundypharma: Research Funding; Takeda: Honoraria, Research Funding; Zenyaku Kogyo: Honoraria; HUYA: Honoraria. Adachi:Daiichi Sankyo Co., Ltd.: Employment. Fujitani:DaiichiSankyo: Employment. Tachibana:Daiichi Sankyo Co., Ltd: Employment. Yoshihara:Daiichi Sankyo Co., Ltd: Employment. Ishizuka:Daiichi Sankyo Co., Ltd: Employment.

Development and Characterization of the Novel Orally Bioavailable EZH1/2 Dual Inhibitor DS-3201

Polycomb repressive complex 2 (PRC2) methylates histone H3 lysine 27 (H3K27) and represses gene expression to regulate cell proliferation and differentiation. Enhancer of zeste homolog 2 (EZH2) or its close homolog EZH1 function as catalytic subunits of PRC2, so there are two PRC2 complexes containing either EZH2 or EZH1. Many reports suggest that inhibiting PRC2 activity through EZH2 knockdown gives rise to anti-cancer effect against hematological and solid cancers.To date, some EZH2 selective inhibitors have demonstrated anti-cancer potential in preclinical and clinical studies. In spite of this promise, there is concern that the efficacy anticipated with EZH2 selective inhibitors may be compromised due to compensation by EZH1 activity.Herein, we describe the novel, orally bioavailable EZH1/2 dual inhibitor DS-3201. This compound strongly and selectively inhibited the methyltransferase activity of both EZH1 and EZH2 with an IC50 value of 10 nM and 6.0 nM, respectively in cell-free enzymatic assays. This compound also suppressed trimethylation of H3K27 in cells (IC50: 0.55 nM) more potently than EZH2 selective inhibitors.In order to identify the anti-cancer spectrum of DS-3201, we tested its in vitro growth inhibition activity against a panel of cancer cell lines including a variety of hematological cancers. Among the panel, hematological cell lines showed particular sensitivity to DS-3201, with GI50 values less than 100 nM, including 1) acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) cell lines harboring fusion genes, such as MLL-AF9, MLL-AF4, or AML1-ETO, 2) diffuse large B-cell lymphoma (DLBCL) cell lines having EZH2 gain-of-function (GOF) mutations, 3) most of the peripheral T-cell lymphoma and multiple myeloma cell lines tested. Our data thus shows this compound has broader anti-cancer activity than EZH2 selective inhibitors, especially in hematology cancers. We also evaluated the in vivo anti-tumor efficacy of DS-3201 against KARPAS-422, a DLBCL tumor xenograft with an EZH2 GOF mutation. A 100 mg/kg once daily oral administration of DS-3201 caused nearly complete tumor regression without any body weight loss and 25 mg/kg administration also showed clear tumor growth delay.Based on these results, we initiated clinical studies of DS-3201 for patients with lymphoma (Clinical trial information: NCT02732275) and for those with AML and ALL (NCT03110354). DisclosuresHonma:Daiichi Sankyo Co., Ltd.: Employment. Adachi:Daiichi Sankyo Co., Ltd.: Employment. Kanno:Asubio Pharma Co., Ltd.: Employment. Watanabe:Daiichi Sankyo Co., Ltd.: Employment. Hirasawa:Daiichi Sankyo Co., Ltd.: Employment. Nosaka:Daiichi Sankyo Co., Ltd.: Employment. Shiroishi:Daiichi Sankyo Co., Ltd.: Employment. Takizawa:Daiichi Sankyo RD Novare Co., Ltd.: Employment. Yasumatsu:Daiichi Sankyo RD Novare Co., Ltd.: Employment. Horiuchi:Daiichi Sankyo Co., Ltd.: Employment. Nakao:Daiichi Sankyo Co., Ltd.: Employment. Suzuki:Daiichi Sankyo Co., Ltd.: Employment. Yamasaki:Daiichi Sankyo Co., Ltd.: Employment. Nakajima:Daiichi Sankyo Co., Ltd.: Employment. Hayakawa:Daiichi Sankyo Co., Ltd.: Employment. Yamazaki:Daiichi Sankyo Co., Ltd.: Employment. Araki:Daiichi Sankyo: Employment. Fujiwara:Daiichi Sankyo Co., Ltd.: Employment.

Clinical Correlations of Polycomb Repressive Complex 2 in Different Tumor Types.

Simple SummaryPRC2 (Polycomb repressive complex 2) is a catalytic multi-subunit complex involved in transcriptional repression through the methylation of lysine 27 at histone 3 (H3K27me1/2/3). Dysregulation of PRC2 has been linked to tumor development and progression. Here, we performed a comprehensive analysis of data in the genomic and transcriptomic (cBioPortal, KMplot) database portals of clinical tumor samples and evaluated clinical correlations of EZH2, SUZ12, and EED. Next, we developed an original Python application enabling the identification of genes cooperating with PRC2 in oncogenic processes for the analysis of the DepMap CRISPR knockout database. Our study identified cancer types that are most likely to be responsive to PRC2 inhibitors. By analyzing co-dependencies with other genes, this analysis also provides indications of prognostic biomarkers and new therapeutic regimens.PRC2 (Polycomb repressive complex 2) is an evolutionarily conserved protein complex required to maintain transcriptional repression. The core PRC2 complex includes EZH2, SUZ12, and EED proteins and methylates histone H3K27. PRC2 is known to contribute to carcinogenesis and several small molecule inhibitors targeting PRC2 have been developed. The present study aimed to identify the cancer types in which PRC2 targeting drugs could be beneficial. We queried genomic and transcriptomic (cBioPortal, KMplot) database portals of clinical tumor samples to evaluate clinical correlations of PRC2 subunit genes. EZH2, SUZ12, and EED gene amplification was most frequently found in prostate cancer, whereas lymphoid malignancies (DLBCL) frequently showed EZH2 mutations. In both cases, PRC2 alterations were associated with poor prognosis. Moreover, higher expression of PRC2 subunits was correlated with poor survival in renal and liver cancers as well as gliomas. Finally, we generated a Python application to analyze the correlation of EZH2/SUZ12/EED gene knockouts by CRISPR with the alterations detected in the cancer cell lines using DepMap data. As a result, we were able to identify mutations that correlated significantly with tumor cell sensitivity to PRC2 knockout, including SWI/SNF, COMPASS/COMPASS-like subunits and BCL2, warranting the investigation of these genes as potential markers of sensitivity to PRC2-targeting drugs.

Phase 1/2 first-in-human (FIH) study of CPI-0209, a novel small molecule inhibitor of enhancer of zeste homolog 2 (EZH2) in patients with advanced tumors.

3104 Background: Enhancer of Zeste homolog 2 (EZH2) is a histone methyltransferase and the catalytic subunit of Polycomb Repressive Complex 2 (PRC2). EZH2 is frequently overexpressed in cancers and correlates with poor prognosis. CPI-0209 is an oral, small molecule, second-generation, selective inhibitor of EZH2 designed to achieve comprehensive target coverage through extended on-target residence time. The compound demonstrates more potent anti-tumor activity in preclinical cancer models, compared to first-generation EZH2 inhibitors. CPI-0209 is currently being evaluated in a Phase 1/2, open-label, FIH study (NCT04104776). Methods: Patients (pts) with advanced tumors were enrolled in a 3+3 design. Primary objective is to determine maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) of CPI-0209. Secondary objectives are to evaluate the safety, PK, and PD in pts who received CPI-0209 QD in 28 days cycles (C). Results: As of December 16, 2020, 33 pts were treated: pancreatic cancer (n = 6), mesothelioma, breast, colorectal, and ovarian cancer (n = 5 each), leiomyosarcoma, melanoma, cholangiocarcinoma, prostate, bladder, endometrial clear cell and gastric cancer (n = 1 each). Pts received CPI-0209 at 50 mg (n = 4), 100 mg, 137.5 mg, and 187.5 mg (n = 6 each), 225 mg (n = 7), and 275 mg (n = 4) daily dose. Median treatment duration was 43 days (range 1-239); 4 pts are ongoing. Median age was 64 yrs (range 24-79); 15 (45%) pts were male. Patients were heavily pretreated, with 67% of pts had ≥ 3 prior lines of therapy. No dose limiting toxicities have been observed. The most frequent treatment-emergent adverse events (TEAEs) (≥10%) were fatigue (27%), diarrhea (24%), nausea (21%), abdominal pain, alopecia, anemia, thrombocytopenia, and dysgeusia (15% each), and vomiting, headache, decreased appetite, and alkaline phosphatase increased (12% each); usually grade 1 or 2 in severity. Thrombocytopenia was dose-dependent and not associated with bleeding or clinical sequalae. Three pts (9%) discontinued CPI-0209 due to TEAEs. Comprehensive target engagement (assessed by global reduction in H3K27me3 levels in monocytes) was observed within the first cycle at all dose levels. CPI-0209 also increased the expression of PRC2-controlled gene sets in blood in a dose-dependent manner. Updated safety, PK, PD, and preliminary efficacy results from Phase 1 will be presented. Conclusions: CPI-0209 achieved robust PD effects and a PK-PD relationship has been established. CPI-0209 monotherapy was generally well tolerated, and treatment related AEs were manageable and reversible. The MTD has not been reached. Clinical trial information: NCT04104776.

EZH2 as an Epigenetic Regulator of Cardiovascular Development and Diseases.

Enhancer of zeste homolog 2(EZH2) is an enzymatic subunit of polycomb repressive complex 2 (PRC2) and is responsible for catalyzing mono-, di-, and trimethylation of histone H3 at lysine-27(H3K27me1/2/3). Many noncoding RNAs or signaling pathways are involved in EZH2 functional alterations. This new epigenetic regulation of target genes is able to silence downstream gene expression and modify physiological and pathological processes in heart development, cardiomyocyte regeneration, and cardiovascular diseases, such as hypertrophy, ischemic heart diseases, atherosclerosis, and cardiac fibrosis. Targeting the function of EZH2 could be a potential therapeutic approach for cardiovascular diseases.

Elevated Expression of DNA Methyltransferases and Enhancer of Zeste Homolog 2 in Helicobacter pylori - Gastritis and Gastric Carcinoma

Aim: The aim of this study was to study the role of key epigenetic regulators pertaining to DNA methylation and histone-modification systems in Helicobacter pylori (HP)-associated gastritis and gastric carcinogenesis. Methods: The expression of DNA methyltransferase (DNMT-1, 3A, and 3B) and the catalytic subunit of polycomb repressive complex-2 (enhancer of zeste homolog 2 [EZH2]) in gastric carcinomas (n = 104), mucosa adjacent to carcinoma (n = 104), HP-associated gastritis (n = 95), and histologically normal mucosa (n = 31) was assessed by immunohistochemistry and qRT-PCR. Results: The expression of all 3 DNMTs and EZH2 was significantly higher in HP-associated gastritis and carcinoma cases than in those with adjacent and normal mucosa. The expression of DNMT-1 and 3B was maximum in HP-associated gastritis. DNMT-3A showed higher expression in carcinoma-adjacent mucosa than in normal mucosa. Interestingly, the expression of EZH2 was higher in cases of HP-associated gastritis with metaplasia than in those without metaplasia and also in cases of intestinal type of adenocarcinoma. Significant positive correlation of EZH2 was identified with DNMT-1, DNMT-3A, and DNMT-3B. However, none of these markers was associated with survival outcome. Conclusion: This study establishes an important role of the key epigenetic regulators in the pathogenesis of both HP-associated gastritis and gastric carcinoma. Higher expression of all the epigenetic markers in the gastritis and their persistence in the carcinoma point toward their implications in HP-driven gastric carcinogenesis. Further, an inter-relation between the 2 arms of epigenetics, namely, DNA methylation and histone-modification in the pathogenesis of gastric carcinoma, is also documented. Given the reversibility of epigenetic phenomenon, these molecules may be of important therapeutic use.

Distinct PRC2 subunits regulate maintenance and establishment of Polycomb repression during differentiation

The Polycomb repressive complex 2 (PRC2) is an essential epigenetic regulator that deposits repressive H3K27me3. PRC2 subunits form two holocomplexes-PRC2.1 and PRC2.2-but the roles of these two PRC2 assemblies during differentiation are unclear. We employed auxin-inducible degradation to deplete PRC2.1 subunit MTF2 or PRC2.2 subunit JARID2 during differentiation of embryonic stem cells (ESCs) to neural progenitors (NPCs). Depletion of either MTF2 or JARID2 resulted in incomplete differentiation due to defects in gene regulation. Distinct sets of Polycomb target genes were derepressed in the absence of MTF2 or JARID2. MTF2-sensitive genes were marked by H3K27me3 in ESCs and remained silent during differentiation, whereas JARID2-sensitive genes were preferentially active in ESCs and became newly repressed in NPCs. Thus, MTF2 and JARID2 contribute non-redundantly to Polycomb silencing, suggesting that PRC2.1 and PRC2.2 have distinct functions in maintaining and establishing, respectively, Polycomb repression during differentiation.

RNF2 Mediates Hepatic Stellate Cells Activation by Regulating ERK/p38 Signaling Pathway in LX-2 Cells.

The therapeutic approach of liver fibrosis is still an unsolved clinical problem worldwide. Notably, the accumulation of extracellular matrix (ECM) in the liver is mediated by the production of cytokines and growth factors, such as transforming growth factor-β1 (TGF-β1) in hepatic stellate cells (HSCs). Ring finger protein 2 (RNF2) was identified as the catalytic subunit of polycomb repressive complex 1 (PRC1), mediating the monoubiquitination of histone H2A. In recent years, a growing amount of evidence suggests that RNF2 may play an important role in multiple pathological processes involved in cancer. Here, we explored the role of RNF2 in liver fibrogenesis and its potential mechanisms. The results showed that RNF2 was up-regulated in human fibrotic liver tissue. Knockdown of RNF2 led to a decreasing expression of collagen1 and α-smooth muscle actin (α-SMA) in LX-2 cells, which was upregulated by RNF2 overexpression. Moreover, RNF2 overexpression significantly promoted TGF-β1-induced LX-2 cell proliferation but decreased apoptosis. Furthermore, knockdown of RNF2 inhibited the activation of ERK/p38 signaling pathways induced by TGF-β1. These data suggested that RNF2 is an effective pro-fibrogenic factor for HSC activation via ERK/p38 signaling pathway. RNF2 inhibition might be a promising therapeutic target for liver fibrosis.

Epigenetic silencing of miR-144/451a cluster contributes to HCC progression via paracrine HGF/MIF-mediated TAM remodeling

Background & AimsHepatocellular carcinoma (HCC) is among the malignancies with the highest mortality. The key regulators and their interactive network in HCC pathogenesis remain unclear. Along with genetic mutations, aberrant epigenetic paradigms, including deregulated microRNAs (miRNAs), exert profound impacts on hepatocyte transformation and tumor microenvironment remodeling; however, the underlying mechanisms are largely uncharacterized.MethodsWe performed RNA sequencing on HCC specimens and bioinformatic analyses to identify tumor-associated miRNAs. The miRNA functional targets and their effects on tumor-infiltrating immune cells were investigated. The upstream events, particularly the epigenetic mechanisms responsible for miRNA deregulation in HCC, were explored.ResultsThe miR-144/miR-451a cluster was downregulated in HCC and predicted a better HCC patient prognosis. These miRNAs promoted macrophage M1 polarization and antitumor activity by targeting hepatocyte growth factor (HGF) and macrophage migration inhibitory factor (MIF). The miR-144/miR-451a cluster and EZH2, the catalytic subunit of polycomb repressive complex (PRC2), formed a feedback circuit in which miR-144 targeted EZH2 and PRC2 epigenetically repressed the miRNA genes via histone H3K27 methylation of the promoter. The miRNA cluster was coordinately silenced by distal enhancer hypermethylation, disrupting chromatin loop formation and enhancer-promoter interactions. Clinical examinations indicated that methylation of this chromatin region is a potential HCC biomarker.ConclusionsOur study revealed novel mechanisms underlying miR-144/miR-451a cluster deregulation and the crosstalk between malignant cells and tumor-associated macrophages (TAMs) in HCC, providing new insights into HCC pathogenesis and diagnostic strategies.

Genetic Impairments of PRC2 Activity in Oncology: Problems and Prospects

PRC2 (Polycomb repressive complex 2) is a conserved protein complex in multicellular organisms that is required to maintain gene repression. The catalytic subunit of PRC2, the EZH2 protein, provides the methylation of histone H3K27 (H3K27me1/2/3). It was demonstrated that a number of human cancers were associated with overexpression of PRC2 subunits, as well as with mutations that enhanced the EZH2 catalytic activity. At the same time, a group of cancers correlate with mutations that inhibit PRC2. A number of small molecule inhibitors to the PRC2 subunits have been developed, primarily to EZH2. One of these, tazemetostat, received approval in January 2020 in the United States for the treatment of epithelioid sarcoma. This review focuses on the role of PRC2 in cancer development and summarizes information on the designed PRC2 inhibitors.

The noncanonical role of EZH2 in cancer.

Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of polycomb repressive complex 2 (PRC2). Dysregulation of EZH2 causes alteration of gene expression and functions, thereby promoting cancer development. The regulatory function of EZH2 varies across different tumor types. The canonical role of EZH2 is gene silencing through catalyzing the trimethylation of lysine 27 of histone H3 (H3K27me3) in a PRC2‐dependent manner. Accumulating evidence indicates that EZH2 has an H3K27me3‐independent function as a transcriptional coactivator and plays a critical role in cancer initiation, development, and progression. In this review, we summarize the regulation and function of EZH2 and focus on the current understanding of the noncanonical role of EZH2 in cancer.