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. Besides, enhanced expression of EZH2 contributes to pathogenesis. Furthermore, the critical role of the retinoic acid signaling pathway in the development and homeostasis of the urothelium is well established. Here we report that coordinated targeting of EZH2 and the retinoic acid signaling pathway caused 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 and orchestrated manner. Moreover, combined treatment caused the modulation of the expression of genes associated with an anti-oncogenic profile, as reflected by the stimulation of marker genes associated with apoptosis and differentiation. 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/EBPβ and CHOP. These findings highlight the importance of co-targeting the EZH2/retinoic acid pathway in bladder cancers and encourage the design of novel treatments employing retinoids coupled with EZH2 inhibitors in bladder carcinoma.