Bradykinin induced mitogenesis of androgen independent prostate cancer cells

Purpose: We investigated the mitogenic role of bradykinin (BK) in the regulation of the extracellular signal regulated kinase 1 and 2 (ERK), and the growth of androgen insensitive prostate cancer cells. Materials and Methods: Androgen insensitive PC3 cells were used in these studies. BK and epidermal growth factor were used as mitogens. The chemical inhibitors tyrphostin AG1478 (epidermal growth factor receptor inhibitor), bisindolylmaliemide (protein kinase C inhibitor) and PD98059 (MEK inhibitor) were applied 30 minutes before stimulation with agonist. Down-regulation of protein kinase C was accomplished by incubating cells overnight with phorbol ester. Cell proliferation was measured using WST-1 reagent and the trypan blue exclusion assay. ERK expression and activation were assayed by immunoblotting for total and phosphorylated ERK. Results: Bradykinin induced the proliferation of PC3 cells in a pathway that requires the activation of ERK. The BK regulated activation of ERK was time and dose dependent, yielding a maximal response at the same concentration range that elicits cellular growth. BK exerted its effect on ERK activation via a protein kinase C and epidermal growth factor receptor dependent pathway. Inhibition of the kinase activity of protein kinase C or epidermal growth factor receptor eliminated BK induced ERK activation. Furthermore, the inhibition of epidermal growth factor receptor transactivation abolished BK induced cell proliferation. Conclusions: Our results show that BK induces the proliferation of androgen insensitive prostate cancer cells and suggest a possible pathophysiological role for BK in prostate cancer.