Retinoids and EZH2 inhibitors cooperate to orchestrate cytotoxic effects on bladder cancer cells
Emerging evidence has highlighted the importance of targeting EZH2 in bladder cancer owing to the highly mutated nature of bladder cancers harboring mutations in chromatin regulatory genes opposing Polycomb-mediated repression, with enhanced expression of EZH2 contributing to pathogenesis. Here we report that coordinated targeting of EZH2 and the retinoic acid signaling pathway caused the cytotoxic effects on bladder cancer cells by inducing a synergistic reduction in proliferative potential that was associated with increased apoptosis and cell cycle arrest in a cooperative manner. Moreover, combined treatment caused the modulation of the expression of certain genes towards an anti-oncogenic profile, as reflected by the stimulation of marker genes associated with apoptosis and differentiation. To investigate the effects on gene regulatory networks associated with fenretinide and GSK-126 treatments at a genome-wide scale, we performed gene expression profiling analysis using data obtained from RNA-seq of T24 cells. We further portrayed a molecular mechanism whereby EZH2 maintains H3K27me3-mediated repression of certain genes associated with unfolded protein response and some metabolic processes. This work also characterized an apoptotic program centered on the master transcriptional regulators C/EBPß and CHOP. Our findings encourage the design of novel treatments employing retinoids coupled with EZH2 inhibitors in bladder carcinoma. Overall design: Comparative gene expression profiling analysis of RNA-seq data for T24 cells. Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) for histone modifications H3K27Me3 in T24 cells.