EZH1/2 as targets for cancer therapy

A novel EZH1/2 dual inhibitor inhibits GCB DLBCL through Cell Cycle Regulation and M2 Tumor-Associated Macrophage Polarization

The incidence of germinal center B-cell-like type diffuse large B-cell lymphoma (GCB DLBCL) is steadily increasing, with a known hereditary component. Although some molecular mechanisms in GCB DLBCL have been elucidated, understanding remains incomplete, limiting the effectiveness of targeted therapies. In GCB DLBCL patients, abnormally high expression of zeste homologs 2 (EZH2) is noted, and the compensatory effect of EZH1 following EZH2 inhibition contributes to poor prognosis. This highlights the potential of dual targeting of EZH1/2 as a promising strategy. In this study, we developed a novel inhibitor, EZH-1-P2, targeting EZH1/2, and evaluated its anti-tumor effects on DLBCL cells. Mechanistically, inhibition of EZH1/2 affects the epigenetic regulation of gene expression related to p53, impacting cell cycle progression and GCB DLBCL cell growth. Additionally, while EZH1/2 inhibition impacts NOTCH signaling, the precise mechanism by which it affects M2-type tumor-associated macrophage (M2-TAM) polarization and germinal center expansion requires further investigation. Our research introduces EZH-1-P2 as a novel inhibitor with potential as a candidate for GCB DLBCL therapy, although further studies are needed to fully elucidate its mechanisms.

Dual-target EZH2 inhibitor: latest advances in medicinal chemistry

Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, plays a crucial role in tumor progression by regulating gene expression. EZH2 inhibitors have emerged as promising anti-tumor agents due to their potential in cancer treatment strategies. However, single-target inhibitors often face limitations such as drug resistance and side effects. Dual-target inhibitors, exemplified by EZH1/2 inhibitor HH-2853(28), offer enhanced efficacy and reduced adverse effects. This review highlights recent advancements in dual inhibitors targeting EZH2 and other proteins like BRD4, PARP1, and EHMT2, emphasizing rational design, structure-activity relationships, and safety profiles, suggesting their potential in clinical applications.

Decline in corepressor CNOT1 in the pregnant myometrium near term impairs progesterone receptor function and increases contractile gene expression

Progesterone (P4), acting via its nuclear receptor (PR), is critical for pregnancy maintenance by suppressing proinflammatory and contraction-associated protein (CAP)/contractile genes in the myometrium. P4/PR partially exerts these effects by tethering to NF-κB bound to their promot-ers, thereby decreasing NF-κB transcriptional activity. However, the underlying mechanisms whereby P4/PR interaction blocks proinflammatory and CAP gene expression are not fully understood. Herein, we characterized CCR-NOT transcription complex subunit 1 (CNOT1) as a corepressor that also interacts within the same chromatin complex as PR-B. In mouse myome-trium increased expression of CAP genes Oxtr and Cx43 at term coincided with a marked decline in expression and binding of CNOT1 to NF-κB-response elements within the Oxtr and Cx43 promoters. Increased CAP gene expression was accompanied by a pronounced decrease in enrichment of repressive histone marks and increase in enrichment of active histone marks to this genomic region. These changes in histone modification were associated with changes in expression of corresponding histone modifying enzymes. Myometrial tissues from P4-treated 18.5 dpc pregnant mice manifested increased Cnot1 expression at 18.5 dpc, compared to vehicle-treated controls. P4 treatment of PR-expressing hTERT-HM cells enhanced CNOT1 expression and its recruitment to PR bound NF-κB-response elements within the CX43 and OXTR promoters. Furthermore, knockdown of CNOT1 significantly increased expression of contractile genes. These novel findings suggest that decreased expression and DNA-binding of the P4/PR-regulated transcriptional corepressor CNOT1 near term and associated changes in histone modifications at the OXTR and CX43 promoters contribute to the induction of myometrial contractility leading to parturition.

EZH2: The roles in targeted therapy and mechanisms of resistance in breast cancer

Drug resistance presents a formidable challenge in the realm of breast cancer therapy. Accumulating evidence suggests that enhancer of zeste homolog 2 (EZH2), a component of the polycomb repressive complex 2 (PRC2), may serve as a key regulator in controlling drug resistance. EZH2 overexpression has been observed in breast cancer and many other malignancies, showing a strong correlation with poor outcomes. This review aims to summarize the mechanisms by which EZH2 regulates drug resistance, with a specific focus on breast cancer, in order to provide a comprehensive understanding of the underlying molecular processes. Additionally, we will discuss the current strategies and outcomes of targeting EZH2 using both single agents and combination therapies, with the goal of offering improved guidance for the clinical treatment of breast cancer patients who have developed drug resistance.

Enhancer of Zeste Homolog 2 Inhibitor SHR2554 in Relapsed or Refractory Peripheral T-cell Lymphoma: Data from the First-in-Human Phase I Study

PURPOSE

Patients with peripheral T-cell lymphomas (PTCL) in the relapsed or refractory (r/r) setting have only a limited number of therapies available, and the prognosis is extremely poor. SHR2554 is an oral inhibitor against EZH2, a rational therapeutic target for lymphomas.

PATIENTS AND METHODS

This was a multicenter, two-part, phase I study of SHR2554 in r/r mature lymphoid neoplasms. In part I, 350 mg twice daily was established as the recommended phase II dose (RP2D) based on the findings during dose escalation and expansion; subsequently, selected lymphoma subtypes were recruited in clinical expansion cohorts to receive SHR2554 at RP2D. Here, we provide an in-depth assessment of SHR2554 at RP2D in subpopulation with r/r PTCL.

RESULTS

Twenty-eight patients were included for analysis (17 angioimmunoblastic T-cell lymphoma and 11 not otherwise specified). Eighteen (64%) patients had received ≥2 lines of previous anticancer therapies. The objective response rate was 61% [95% confidence interval (CI), 41-78]. Responses were still ongoing in 59% (10/17) of the responders; estimated median duration of response was 12.3 months (95% CI, 7.4-not reached). Median progression-free survival was 11.1 months (95% CI, 5.3-22.0), and 12-month overall survival rate was 92% (95% CI, 72-98). The most common grade 3 or 4 treatment-related adverse events were decreased platelet count [nine (32%)] as well as decreased white blood cell count, decreased neutrophil count, and anemia [four (14%) for each]. No treatment-related deaths were reported.

CONCLUSIONS

This extended follow-up analysis further supports SHR2554 as a therapeutic opportunity for patients with r/r PTCL.

The competitive mechanism of EZH1 and EZH2 in promoting oral squamous cell carcinoma

Enhancer of Zeste Homolog 1 (EZH1) and Enhancer of Zeste Homolog 2 (EZH2) are the key components of polycomb repressive complex 2 (PRC2); however, the roles of these proteins in oral squamous cell carcinoma (OSCC) have yet to be elucidated. In this study, we aimed to determine the respective roles of these proteins in OSCC by investigating the expression levels of EZH1 and EZH2 in OSCC tissues (N = 63) by immunohistochemistry. In addition, we used lentiviruses to construct stable OSCC cell lines that overexpressed EZH1 and EZH2. Then, we investigated these cell lines for cell viability, colony formation capacity, stemness, and epithelial-mesenchymal transition (EMT). Binding competition between EZH1 and EZH2 with PRC2 was further evaluated using Co-immunoprecipitation (Co-IP). Compared with normal tissues, the expression levels of EZH2 in OSCC tissues was up-regulated, while the expression of EZH1 was down-regulated. EZH2 enhanced cell viability, colony formation capacity, stemness, and EMT, while EZH1 did not. Furthermore, analysis indicated that EZH1 and EZH2 bound competitively to PRC2 and influenced the methylation status of H3K27. In conclusion, our findings verified that EZH1 and EZH2 play opposing roles in OSCC and that EZH1 and EZH2 compete as the key component of PRC2, thus affecting the characteristics of OSCC via the methylation of H3K27.

A miniaturized mode-of-action profiling platform enables high throughput characterization of the molecular and cellular dynamics of EZH2 inhibition

The market approval of Tazemetostat (TAZVERIK) for the treatment of follicular lymphoma and epithelioid sarcoma has established "enhancer of zeste homolog 2" (EZH2) as therapeutic target in oncology. Despite their structural similarities and common mode of inhibition, Tazemetostat and other EZH2 inhibitors display differentiated pharmacological profiles based on their target residence time. Here we established high throughput screening methods based on time-resolved fluorescence energy transfer, scintillation proximity and high content analysis microscopy to quantify the biochemical and cellular binding of a chemically diverse collection of EZH2 inhibitors. These assays allowed to further characterize the interplay between EZH2 allosteric modulation by methylated histone tails (H3K27me3) and inhibitor binding, and to evaluate the impact of EZH2's clinically relevant mutant Y641N on drug target residence times. While all compounds in this study exhibited slower off-rates, those with clinical candidate status display significantly slower target residence times in wild type EZH2 and disease-related mutants. These inhibitors interact in a more entropy-driven fashion and show the most persistent effects in cellular washout and antiproliferative efficacy experiments. Our work provides mechanistic insights for the largest cohort of EZH2 inhibitors reported to date, demonstrating that-among several other binding parameters-target residence time is the best predictor of cellular efficacy.

Synthesis and application of small molecules approved for the treatment of lymphoma

Lymphoma is a form of cancer that impacts the lymphatic system, which plays a crucial role in defending the body against infections and illnesses. It is characterized by the atypical proliferation of lymphocytes, a type of white blood cell, which can form tumors in the lymph nodes, bone marrow, spleen, etc. Lymphoma is usually treated using a combination of targeted therapy, chemotherapy, and radiation therapy. In recent years, there has been a growing interest in the development of new drugs to treat lymphoma, which has led to the discovery of several promising compounds. The primary targets for lymphoma treatment have been identified as Bruton's tyrosine kinase (BTK), phosphoinositide3-kinase (PI3K), histone deacetylase (HDAC), and DNA polymerase (POLA). This review aims to provide an overview of the clinical applications and synthesis of several notable drugs approved to treat lymphoma, to expedite the exploration of more potent novel medications for the management of lymphoma.

Targeting EZH2 in SMARCB1-deficient sarcomas: Advances and opportunities to potentiate the efficacy of EZH2 inhibitors

Soft tissue sarcomas (STSs) are rare mesechymal malignancies characterized by distintive molecular, histological and clinical features. Many STSs are considered as predominatly epigenetic diseases due to underlying chromatin deregulation. Discovery of deregulated functional antagonism between the chromatin remodeling BRG1/BRM-associated (BAFs) and the histone modifying Polycomb repressor complexes (PRCs) has provided novel actionable targets. In epithelioid sarcoma (ES), extracranial, extrarenal malignant rhabdoid tumors (eMRTs) and synovial sarcoma (SS), the total or partial loss of the BAF core subunit SMARCB1, driven by different alterations, is associated with PRC2 deregulation and dependency on its enzymatic subunit, EZH2. In these SMARCB1-deficient STSs, aberrant EZH2 expression and/or activity emerged as a druggable vulnerability. Although preclinical investigation supported EZH2 targeting as a promising therapeutic option, clinical studies demonstrated a variable response to EZH2 inhibitors. Actually, whereas the clinical benefit recorded in ES patients prompted the FDA approval of the EZH2 inhibitor tazemetostat, the modest and sporadic responses observed in eMRT and SS patients highlighted the need to deepen mechanistic as well as pharmacological investigations to improve drug effectiveness. We summarize the current knowledge of different mechanisms driving SMARCB1 deficiency and EZH2 deregulation in ES, eMRT and SS along with preclinical and clinical studies of EZH2-targeting agents. Possible implication of the PRC2- and enzymatic-independent functions of EZH2 and of its homolog, EZH1, in the response to anti-EZH2 agents will be discussed together with combinatorial strategies under investigation to improve the efficacy of EZH2 targeting in these tumors.

Genomic and Epigenetic Changes Drive Aberrant Skeletal Muscle Differentiation in Rhabdomyosarcoma

Rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children and adolescents, represents an aberrant form of skeletal muscle differentiation. Both skeletal muscle development, as well as regeneration of adult skeletal muscle are governed by members of the myogenic family of regulatory transcription factors (MRFs), which are deployed in a highly controlled, multi-step, bidirectional process. Many aspects of this complex process are deregulated in RMS and contribute to tumorigenesis. Interconnected loops of super-enhancers, called core regulatory circuitries (CRCs), define aberrant muscle differentiation in RMS cells. The transcriptional regulation of MRF expression/activity takes a central role in the CRCs active in skeletal muscle and RMS. In PAX3::FOXO1 fusion-positive (PF+) RMS, CRCs maintain expression of the disease-driving fusion oncogene. Recent single-cell studies have revealed hierarchically organized subsets of cells within the RMS cell pool, which recapitulate developmental myogenesis and appear to drive malignancy. There is a large interest in exploiting the causes of aberrant muscle development in RMS to allow for terminal differentiation as a therapeutic strategy, for example, by interrupting MEK/ERK signaling or by interfering with the epigenetic machinery controlling CRCs. In this review, we provide an overview of the genetic and epigenetic framework of abnormal muscle differentiation in RMS, as it provides insights into fundamental mechanisms of RMS malignancy, its remarkable phenotypic diversity and, ultimately, opportunities for therapeutic intervention.

Recent advances in EZH2-based dual inhibitors in the treatment of cancers

The enhancer of zeste homolog 2 (EZH2) protein is the catalytic subunit of one of the histone methyltransferases. EZH2 catalyzes the trimethylation of lysine 27 of histone H3 (H3K27me3) and further alters downstream target levels. EZH2 is upregulated in cancer tissues, wherein its levels correlate strongly with cancer genesis, progression, metastasis, and invasion. Consequently, it has emerged as a novel anticancer therapeutic target. Nonetheless, developing EZH2 inhibitors (EZH2i) has encountered numerous difficulties, such as pre-clinical drug resistance and poor therapeutic effect. The EZH2i synergistically suppresses cancers when used in combination with additional antitumor drugs, such as PARP inhibitors, HDAC inhibitors, BRD4 inhibitors, EZH1 inhibitors, and EHMT2 inhibitors. Typically, the use of dual inhibitors of two different targets mediated by one individual molecule has been recognized as the preferred approach for overcoming the limitations of EZH2 monotherapy. The present review discusses the theoretical basis for designing EZH2-based dual-target inhibitors, and also describes some in vitro and in vivo analysis results.

Can Patients with HER2-Low Breast Cancer Benefit from Anti-HER2 Therapies? A Review

Breast cancer (BC) poses a severe threat to the health of women worldwide. Currently, different therapeutic regimens are used for BC according to the pathological classification of HER2-positive or HER2-negative. Clinical reports of HER2-low expression indicate that the condition is HER2-negative, which was ineligible for HER2-targeted therapy. In contrast to HER2-zero tumors, however, HER2-low BC is a heterogeneous disease with unique genetic characteristics, prognoses, and different therapeutic responses. Clinical efficacy has been demonstrated by numerous potent and innovative anti-HER2 medications, particularly antibody-drug conjugates (ADCs). Certain ADCs, including T-DXd, have demonstrated good efficacy in some trials either used alone or in conjunction with other medications. To enhance outcomes in individuals with HER2-low BC, immunotherapy and other treatments are frequently combined with HER2-targeted therapy. There are also alternative strategies that target both HER2 and HER3 or other antigenic sites. We hope more individuals with HER2-low BC will benefit from more precise treatment regimens in the future. This article provides a review of existing research and clinical trials.

Beyond Expression: Role of Phosphorylated Residues of EZH2 in Lineage Plasticity in Prostate Cancer

Despite the development of effective targeted therapies and a significant understanding of carcinogenesis and cancer progression, treatment resistance is a major obstacle in achieving durable long-term control in many types of cancers. Emerging evidence supports that nongenetic mechanisms could play an underappreciated role in therapy resistance. These mechanisms include phenotypic plasticity, which is recognized as a hallmark of cancer and translates to epigenetic and transcriptional control of gene expression. Alterations in the expression and activity of the epigenetic modifier enhancer of zeste homolog 2 (EZH2) support prostate cancer lineage plasticity and progression. EZH2 expression and activity is elevated in castration-resistant prostate cancer treated with androgen receptor pathway inhibitors and in treatment-resistant prostate cancer. Moreover, 17 known residues of EZH2 are phosphorylated on by multiple kinases that modulate its activity, localization, stability, and polycomb repressive complex (PRC2) assembly. In this review, we explore the contribution of EZH2 phosphorylation in regulating canonical PRC2 in a methylation-dependent manner as an epigenetic repressor and in a noncanonical manner independent of PRC2 as a transcription activator. Apart from the contribution of EZH2 phosphorylation at serine 21, threonine 350, and threonine 311 in prostate cancer progression and treatment resistance, we discuss how other EZH2 phosphorylated residues with unknown functions could contribute to prostate cancer based on their upstream regulators and potential therapeutic utility.

The role and application of transcriptional repressors in cancer treatment

Gene expression is modulated through the integration of many regulatory elements and their associated transcription factors (TFs). TFs bind to specific DNA sequences and either activate or repress transcriptional activity. Through decades of research, it has been established that aberrant expression or functional abnormalities of TFs can lead to uncontrolled cell division and the development of cancer. Initial studies on transcriptional regulation in cancer have focused on TFs as transcriptional activators. However, recent studies have demonstrated several different mechanisms of transcriptional repression in cancer, which could be potential therapeutic targets for the development of specific anti-cancer agents. In the first section of this review, "Emerging roles of transcriptional repressors in cancer development," we summarize the current understanding of transcriptional repressors and their involvement in the molecular processes of cancer progression. In the subsequent section, "Therapeutic applications," we provide an updated overview of the available therapeutic targets for drug discovery and discuss the new frontier of such applications.