Precision Targeting with EZH2 and HDAC Inhibitors in Epigenetically Dysregulated Lymphomas

Abstract

Purpose: Both gain-of-function enhancer of zeste homolog 2 (EZH2) mutations and inactivating histone acetyltransferases mutations, such as CREBBP and EP300, have been implicated in the pathogenesis of germinal center (GC)derived lymphomas. We hypothesized that direct inhibition of EZH2 and histone deacetyltransferase (HDAC) would be synergistic in GC-derived lymphomas.Experimental Design: Lymphoma cell lines (n ¼ 21) were exposed to GSK126, an EZH2 inhibitor, and romidepsin, a pan-HDAC inhibitor. Synergy was assessed by excess over bliss. Western blot, mass spectrometry, and coimmunoprecipitation were performed. A SU-DHL-10 xenograft model was utilized to validate in vitro findings. Pretreatment RNAsequencing of cell lines was performed. MetaVIPER analysis was used to infer protein activity.Results: Exposure to GSK126 and romidepsin demonstrated potent synergy in lymphoma cell lines with EZH2 dysregulation. Combination of romidepsin with other EZH2 inhibitors also demonstrated synergy suggesting a class effect of EZH2 inhibition with romidepsin. Dual inhibition of EZH2 and HDAC led to modulation of acetylation and methylation of H3K27. The synergistic effects of the combination were due to disruption of the PRC2 complex secondary to acetylation of RbAP 46/48. A common basal gene signature was shared among synergistic lymphoma cell lines and was characterized by upregulation in chromatin remodeling genes and transcriptional regulators. This finding was supported by metaVIPER analysis which also revealed that HDAC 1/2 and DNA methyltransferase were associated with EZH2 activation.Conclusions: Inhibition of EZH2 and HDAC is synergistic and leads to the dissociation of PRC2 complex. Our findings support the clinical translation of the combination of EZH2 and HDAC inhibition in EZH2 dysregulated lymphomas.

Inhibition of HDAC1/2 Along with TRAP1 Causes Synthetic Lethality in Glioblastoma Model Systems

“…The methyltransferase EZH2 is mostly known to modulate histone methylation and is part of the PRC2 complex [ 28 , 29 ]. How the PRC2 complex is related to HDACs has been recently demonstrated by others, revealing an interaction between HDAC2 and the PRC2 complex [ 30 ]. Once HDAC2 is inhibited the PRC2 complex becomes hyper-acetylated and dissociates along with its ability to methylate histones [ 30 ], which in concert may result in less methylation of H3K27 and thereby facilitate the up-regulation of genes.…”

Histone Deacetylase Inhibitors in Pediatric Brain Cancers: Biological Activities and Therapeutic Potential

“…The HDACi TSA inhibits HDAC6, a predominantly cytoplasmic HDAC, which likely induces many effects independent of alterations in gene expression stimulated by histone acetylation (Johnstone and Licht, 2003;Chen et al, 2005;Glozak et al, 2005). When combined with agents targeting other epigenetic regulators, such as EZH2, HDACis modulate acetylation and methylation of H3K27, through mechanisms involving PRC2 complex disruption (Lue et al, 2019). Below, we summarize studies examining the effects of HDACis in experimental models of pediatric brain tumors.…”

EZH2 abnormalities in lymphoid malignancies: underlying mechanisms and therapeutic implications

“…Since the year 2012, several serials of specific EZH2 inhibitors, which compete with S-adenosylmethionine for the binding to EZH2 enzymatic SET domain, have been reported (Table 2). These inhibitors could suppress H3K27 tri-methylation, reactivate silenced PRC2 target genes and demonstrated effectiveness in inhibition of cell survival in GC-derived B cell lymphomas harboring EZH2-activating mutations amid several types of lymphoid malignancies [35,[122][123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140].…”

“…Treatment with this peptide in NKTL cells also inhibits H3K27 tri-methylation, but leaves EZH2 expression intact [69]. Astemizole, originally a second-generation [122]; Lue JK., et al [123]; Adamik J., et al [124]; Zeng D., et al [125]; Ott HM., et al [126]; McCabe MT., et al [35] GSK343 MM Ezponda T., et al [127] EI1 EZH2-mutant GC-DLBCL Qi W., et al [128] EPZ-6438 EZH2-mutant and wild-type GC-DLBCL, MM Herviou L., et al [129]; Dimopoulos K., et al [130]; Brach D., et al [131]; Knutson SK., et al [132] EPZ005687 EZH2-mutant and wild-type GC-DLBCL Knutson SK., et al [133] EPZ011989 EZH2-mutant GC-DLBCL Campbell JE., et al [134] EBI-2511 EZH2-mutant GC-DLBCL Lu B., et al [135] ZLD10A EZH2-mutant GC-DLBCL Song X., et al [136] DCE_42/254 EZH2-mutant and wild-type GC-DLBCL Wu Y., et al [137] CPI-1205 EZH2-mutant GC-DLBCL Vaswani RG., et al [138] Tetramethylpiperidinyl Benzamides EZH2-mutant GC-DLBCL Nasveschuk CG., et al [139] Abbreviations anti-histamine, was withdrawn due to its potential to cause arrhythmia. Later studies uncovered that Astemizole could disrupt EZH2-EED interaction and arrest cell proliferation in some B cell lymphoma cell lines [150].…”

“…Synergistic or re-sensitizing effects between EZH2 inhibitors and traditional cytotoxic anti-cancer drugs have been seen [155,156]. In view of the abundantly present epigenetic abnormalities of H3K27 tri-methylation and histone acetylation, a couple of studies have combined EZH2 inhibitors with different HDAC inhibitors for the treatment in MM [157,158] and B cell lymphoma cells [54,123,159,160], and favorable therapeutic coordination were observed. Dual-targeting of MYC and EZH2 has been employed to disrupt MYC-EZH2 oncogenic axis in aggressive B cell lymphoma cells [51].…”