In this study, we aimed to investigate the angiogenic cytokine profiles of hormone- and drug-refractory prostate carcinoma cell lines, PC-3 and DU-145. We also studied the effect of gossypol, a natural polyphenolic cotton-seed extract, on the angiogenic cytokine profile of these cell lines. XTT cell proliferation assay was used for the assessment of cytotoxicity. For apoptosis, both histone-DNA fragmentation by ELISA assay and caspase 3/7 activity measurement were used. Angiogenic cytokine profiles of supernatants from both cell lines, before and after treatment with gossypol, were investigated using the human angiogenesis antibody array I (R). It was shown that the two different hormone- and drug-resistant prostate cancer cell lines, PC-3 and DU-145, constitutively express some important angiogenic cytokines, which are known to regulate tumorigenicity and angiogenesis in hormone- refractory prostate cancer. However, PC-3 and DU-145 cells have distinct angiogenic cytokine profiles. In addition, these two cells lines respond differently to gossypol treatment in terms of cytotoxicity and angiogenic cytokine secretion. After treatment with 10 mu M of gossypol, there was a 1.5-fold decrease in angiogenin and IL-8 levels and a 1.7- and 1.8-fold decrease in ENA-78 and GRO-alpha levels respectively, in DU-145 cells. For PC-3 cells, there were 1.6- and 1.8-fold decreases in IL-8 and VEGF levels, respectively. We conclude that PC-3 and DU-145 cells secrete significant amounts of different angiogenic cytokines that may explain their aggressive nature and metastatic potential. Gossypol treatment affects angiogenic cytokine secretion from these two cell lines in a different manner. By expanding our knowledge of the heterogeneous biological behavior of these two cell lines, novel treatment approaches can be developed for the treatment of prostate cancer.