Androgen-deprivation therapy with enzalutamide enhances prostate cancer metastasis via decreasing the EPHB6 suppressor expression

Early studies suggested that using ADT with the recently developed anti-androgen Enzalutamide (Enz, also named as MDV3100 could extent castration resistant prostate cancer (CRPC) patients' survival an extra 4.8 months. Yet the therapy in most patients might eventually fail due to development of Enz-resistance. Here we found Enz might also increase some unwanted side-effects via increasing the CRPC cell invasion that might involve altering the Enz-mediated androgen receptor (AR)/EPHB6 suppressor/JNK signaling. Results from multiple clinical surveys also indicated that EPHP6 might function as a suppressor of PCa metastasis. Mechanism dissection revealed that Enz-mediated AR might function via binding to the androgen-response-element (ARE) on the EPHB6 promoter to decrease EPHB6 suppressor expression, which might then activate the phosphorylation of JNK signals to increase the CRPC cell invasion. Targeting this newly identified AR/EPHB6/JNK signaling with JNK inhibitor (SP600125) may then block/reverse the Enz-increased CRPC cell invasion. Collectively, our results suggest that Enz may increase CRPC cell invasion via altering the AR/EPHB6/JNK/MMP9 signaling and targeting this newly identified signaling may help us to increase the Enz efficacy to better suppress the CRPC at the later metastatic stage.