Examining the effects of BET, HDAC2, and EZH2 inhibition on esophageal adenocarcinoma (EAC) cell line proliferation.

Abstract

68 Background: EACs often carry amplifications in MYC (19%) and mutations in the SWI/SNF complex (13%) which act as oncogenic drivers. Targeting of MYC-amplified tumors via BET inhibition, as well as HDAC2 or EZH2 inhibition in SWI/SNF-mutated tumors, show promise in hematological cancers, and solid tumors, respectively. Herein, we investigate the effects of BET, HDAC2, and EZH2 inhibition on EAC cell line proliferation. Methods: MYC-wild type (n = 5), MYC-amplified (n = 2), SWI/SNF-wild type (n = 6) and SWI/SNF-mutant (n = 1) EAC cell lines that have undergone whole genome sequencing (WGS) were plated at 10% confluency and treated with BET (JQ1), pan-HDAC (SAHA), and EZH2 (EPZ-6438) inhibitors at various concentrations. The CellTiter-Glo cell proliferation assay was used to compare the effects of drug treatment on proliferation between different cell lines and drug concentrations before and after treatment. Results: MYC-amplified EAC cell lines were more sensitive to BET inhibition (Table); GI50 concentrations for JQ1 are comparable to those achieved in melanoma and lymphoma cell lines, cancer types in which clinical activity has been demonstrated. ERBB2 amplified or ERBB2 mutant EAC cells were also sensitive to BET inhibition. HDAC2 inhibition reduced proliferation of both SWI/SNF-wild type and mutant cell lines at high concentrations, whilst all cell lines were resistant to EZH2 inhibition, even at the highest concentrations used. Conclusions: MYC amplified EAC tumors appear to be sensitive to BET inhibition; these results warrant further evaluation in pre-clinical models and clinical trials. HDAC2 and EZH2 inhibition were ineffective in both the SWI/SNF-wild type and mutant type EAC cell lines; these therapies are less likely to provide benefit for EAC patients. [Table: see text]