Histone Modifications and Their Targeting in Lymphoid Malignancies

YPEL2 regulates the efficacy of BRD4-EZH2 dual targeting in EZH2Y641mut germinal center-derived lymphoma

A significant proportion of diffuse large B cell lymphoma (DLBCL) and follicular lymphoma (FL) cases harbor a gain-of-function, heterozygous somatic mutation of the methyltransferase gene EZH2. While this factor is known to cooperate with the proto-oncogene MYC during malignant B cell development, the effect of interfering with both factors remains underexplored. Here we undertook the simultaneous evaluation of two epigenetic drugs targeting EZH2 methyltransferase activity and BRD4-mediated control of MYC transcription, CPI169 and CPI203, using preclinical models of DLBCL and FL with distinct EZH2 mutational status. We observed a specific and synergistic antiproliferative effect of these compounds in EZH2-mutated cells and mouse xenograft models, that was related to the abrogation of MYC transcriptional program and to tumor cell proliferation blockade at the G1 cell cycle phase. Gene expression profile, exploratory data analysis, and siRNA screening identified the PI3K/AKT-regulated gene and mitosis regulator, YPEL2, as a crucial factor involved in the efficacy of MYC/EZH2 dual targeting both in vitro and in vivo. Altogether, our results provide first pre-clinical evidence that simultaneous targeting of MYC and EZH2 is a safe and efficient approach that can be monitored by specific biomarkers, in aggressive lymphoid tumors of germinal center origin.

Advances in the treatment of relapsed/refractory marginal zone lymphoma

Marginal zone lymphoma (MZL) is the second most common subtype of inert B-cell non-Hodgkin's lymphoma, accounting for 5-15% of non-Hodgkin's lymphoma cases. Patients with MZL have a long survival period, with a median survival of >10 years, and patients treated with a combination of anti-CD20 monoclonal antibody can achieve an overall effective rate of 81%. However, 20% of patients with MZL show relapse or experience disease progression within 2 years, with a median survival of only 3-5 years. Currently, the treatment options for patients with relapsed/refractory (R/R) MZL are limited, underscoring the pressing need for novel therapeutic drugs. The advent of novel anti-CD20 monoclonal antibodies, small molecule kinase inhibitors, immunomodulators, and other therapeutic strategies has ushered in a new era in the treatment of R/R MZL. Our objective is to summarize the existing treatment strategies, including immunotherapy and the emergent targeted therapies, and to evaluate their effectiveness and safety in the management of R/R MZL. By doing so, we aim to provide a clear understanding of the therapeutic landscape for R/R MZL, and to guide future research directions toward improving the prognosis and quality of life for patients afflicted with this challenging disease.

Targeting the MYC interaction network in B-cell lymphoma via histone deacetylase 6 inhibition

Overexpression of MYC is a genuine cancer driver in lymphomas and related to poor prognosis. However, therapeutic targeting of the transcription factor MYC remains challenging. Here, we show that inhibition of the histone deacetylase 6 (HDAC6) using the HDAC6 inhibitor Marbostat-100 (M-100) reduces oncogenic MYC levels and prevents lymphomagenesis in a mouse model of MYC-induced aggressive B-cell lymphoma. M-100 specifically alters protein-protein interactions by switching the acetylation state of HDAC6 substrates, such as tubulin. Tubulin facilitates nuclear import of MYC, and MYC-dependent B-cell lymphoma cells rely on continuous import of MYC due to its high turn-over. Acetylation of tubulin impairs this mechanism and enables proteasomal degradation of MYC. M-100 targets almost exclusively B-cell lymphoma cells with high levels of MYC whereas non-tumor cells are not affected. M-100 induces massive apoptosis in human and murine MYC-overexpressing B-cell lymphoma cells. We identified the heat-shock protein DNAJA3 as an interactor of tubulin in an acetylation-dependent manner and overexpression of DNAJA3 resulted in a pronounced degradation of MYC. We propose a mechanism by which DNAJA3 associates with hyperacetylated tubulin in the cytoplasm to control MYC turnover. Taken together, our data demonstrate a beneficial role of HDAC6 inhibition in MYC-dependent B-cell lymphoma.

Targeting Epigenetic Regulatory Enzymes for Cancer Therapeutics: Novel Small-Molecule Epidrug Development

Dysregulation of the epigenetic enzyme-mediated transcription of oncogenes or tumor suppressor genes is closely associated with the occurrence, progression, and prognosis of tumors. Based on the reversibility of epigenetic mechanisms, small-molecule compounds that target epigenetic regulation have become promising therapeutics. These compounds target epigenetic regulatory enzymes, including DNA methylases, histone modifiers (methylation and acetylation), enzymes that specifically recognize post-translational modifications, chromatin-remodeling enzymes, and post-transcriptional regulators. Few compounds have been used in clinical trials and exhibit certain therapeutic effects. Herein, we summarize the classification and therapeutic roles of compounds that target epigenetic regulatory enzymes in cancer treatment. Finally, we highlight how the natural compounds berberine and ginsenosides can target epigenetic regulatory enzymes to treat cancer.