Bradykinin induced mitogenesis of androgen independent prostate cancer cells

Purpose: We investigated the mitogenic role of bradykinin (BK) in the regul ation of the extracellular signal regulated kinase 1 and 2 (ERK), and the g rowth of androgen insensitive prostate cancer cells. Materials and Methods: Androgen insensitive PC3 cells were used in these st udies. BK and epidermal growth factor were used as mitogens. The chemical i nhibitors tyrphostin AG1478 (epidermal growth factor receptor inhibitor), b isindolylmaliemide (protein kinase C inhibitor) and PD98059 (MEK inhibitor) were applied 30 minutes before stimulation with agonist. Downregulation of protein kinase C was accomplished by incubating cells overnight with phorb ol ester. Cell proliferation was measured using WST-1 reagent and the trypa n blue exclusion assay. ERK expression and activation were assayed by immun oblotting for total and phosphorylated ERK. Results: Bradykinin induced the proliferation of PC3 cells in a pathway tha t requires the activation of ERK. The BK regulated activation of ERK was ti me and dose dependent, yielding a maximal response at the same concentratio n range that elicits cellular growth. BK exerted its effect on ERK activati on via a protein kinase C and epidermal growth factor receptor dependent pa thway. Inhibition of the kinase activity of protein kinase C or epidermal g rowth factor receptor eliminated BK induced ERK activation. Furthermore, th e 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 pathophysiologica l role for BK in prostate cancer.