Epithelial to mesenchymal plasticity (EMP) has been linked to metastasis, stemness, and drug resistance. In prostate cancer (PCa), EMP has been associated with both suppression and activation of androgen receptor (AR) signaling. Here we investigated the effect of the potent AR antagonist enzalutamide on EMP in multiple preclinical models of PCa and patient tissues. Enzalutamide treatment significantly enhanced the expression of EMP drivers (ZEB1, ZEB2, Snail, Twist, and FOXC2) and mesenchymal markers (N-cadherin, fibronectin, and vimentin) in PCa cells, enhanced PCa cell migration, and induced PCa transformation to a spindle, fibroblast-like morphology. Enzalutamide-induced EMP required concomitant suppression of AR signaling and activation of the EMP-promoting transcription factor Snail, as evidenced by both knockdown and over-expression studies. Supporting these findings, AR signaling and Snail expression were inversely correlated in C4-2 xenografts, patient-derived castration-resistant metastases, and clinical samples. For the first time, we elucidate a mechanism explaining the inverse relationship between AR and Snail: specifically, we found that AR directly repressed SNAIL gene expression by binding to specific AR-responsive elements within the SNAIL promoter. Collectively, our findings demonstrate that de-repression of Snail and induction of EMP is an adaptive response to enzalutamide with implications for therapy resistance.
- Received August 14, 2016.
- Revision received March 5, 2017.
- Accepted March 7, 2017.
- Copyright ©2017, American Association for Cancer Research.