The protein kinase C activator, phorbol ester, elicits disparate functional responses in androgen-sensitive and androgen-independent human prostatic cancer cells.

The protein kinase C (PKC) activator 12-O-tetradecanoyl-phorbol-13-acetate (TPA) activated cell death in androgen-sensitive LNCaP cells but not in androgen-independent DU-145 or PC-3 cells, whose growth was significantly decreased by PKC inhibitors staurosporine and H7. All cell lines had similar levels of total PKC activities which, however, differed on their dependency on Ca2+ ions and lipid and were regulated differently by TPA. Furthermore, expression of the immediate early genes c-fos and c-jun was up-regulated by TPA only in LNCaP and DU-145 cells, whereas PC-3 cells failed to express c-fos mRNA. The regulation of the c-myc mRNA by TPA correlated inversely with activation of cell death being down-regulated in LNCaP cells, and slightly increased in the androgen-independent cell lines. These results suggest that the PKC signal transduction pathway functions differently in androgen-sensitive and insensitive prostatic cells.