We examined effects of TNP-470 with or without nicardipine on in vivo or in vitro growth of a hormone-independent human prostate carcinoma cell line, PC-3. TNP-470 (30 mg/kg, daily) or nicardipine (25 microg/kg, daily) alone had little effects on in vivo growth of PC-3 cells in nude mice, whereas simultaneous administration of both agents significantly inhibited the growth of the xenografts. In vitro proliferation of PC-3 was not affected by TNP-470 and/or nicardipine. Combination of TNP-470 and nicardipine seems beneficial in the treatment of hormone-refractory prostate cancer.