EPHB4 and prostate cancer: EphB4 knockdown lowered EphB4 and the PI3K downstream markers pAKT (Thr308) and phosphorylated ribosomal protein S6 (pS6, Ser235/Ser236; Fig. 6a) in PC3 and castrate-resistant prostate cancer cell lines C4-2B and 22Rv1.