The effects of androgen manipulation on epidermal growth factor (EGF) receptor, p185(erbB-2) and transforming growth factor-α (TGF-α) levels were examined in prostatic adenocarcinoma. Male nude mice were inoculated with the CWR22 androgen-dependent human prostatic tumor or an androgen-independent (CWR22R) derivative. Mice with CWR22 tumors were castrated and subsequently killed at 3, 7, 21, 28 or 42 days post-castration. Other CWR22-bearing mice received s.c. testosterone pellets at 21 days post-castration and were killed 7 days later. EGF receptor, p185(erbB-2) and TGF-α levels were examined by immuno-histochemistry. Strong EGF receptor and p 185(erbB-2) immunostaining was detected in CWR22 tumors from intact controls. EGF receptor immunostaining decreased by 65% to 70% at 21 to 42 days post-castration. Testosterone treatment at 21 to 28 days post-castration resulted in a 2-fold increase in EGF receptor immunostaining, p185(erbB-2) immunostaining within CWR22 tumors did not decrease following castration and, in fact, was slightly increased at 7 days post-castration. The effects of castration on EGF receptor and p1865(erbB-2) levels were confirmed by Western blot analysis. Fewer than 10% of CWR22 tumor cells demonstrated strong TGF-α immunostaining, and androgen manipulation did not effect TGF-α immunostaining. In contrast, 30% of androgen-independent CWR22R tumor cells were strongly immunostained for TGF-α. Our findings indicate that EGF receptor levels, but not p185(erbB-2) levels, are strongly dependent on testosterone in CWR22 tumors. The co-localization of TGF-α and the EGF receptor in CWR22R tumors suggests that these factors may constitute an autocrine pathway that regulates androgen-independent growth.