Combined effects of terazosin and genistein on a metastatic, hormone-independent human prostate cancer cell line

Metastatic prostate cancer progresses from androgen-dependent to androgen-independent. Terazosin, a long-acting selective α1-adrenoreceptor antagonist, induces apoptosis of prostate cancer cells in an α1-adrenoreceptor-independent manner, while genistein, a major soy isoflavone, inhibits the growth of several types of cancer cells. The present study was designed to test the therapeutic potential of a combination of terazosin and genistein using a metastatic, hormone-independent prostatic cancer cell line, DU-145.Terazosin or genistein treatment inhibited the growth of DU-145 cells in a dose-dependent manner, whereas had no effect on normal prostate epithelial cells. Addition of 1 μg/ml of terazosin, which was inactive alone, augmented the growth inhibitory effect of 5 μg/ml of genistein. Co-treatment with terazosin resulted in the genistein-induced arrest of DU-145 cells in G2/M phase being overridden and an increase in apoptotic cells, as evidenced by procaspase-3 activation and PARP cleavage. The combination also caused a greater decrease in the levels of the apoptosis-regulating protein, Bcl-XL, and of VEGF165 and VEGF121 than genistein alone.In conclusion, the terazosin/genistein combination was more effective in inhibiting cell growth and VEGF expression as well as inducing apoptosis of the metastatic, androgen-independent prostate cancer cell line, DU-145, than either alone. The doses used in this study are in lower and nontoxic anticancer dosage range, suggesting this combination has potential for therapeutic use.