Identification of protein kinase C zeta isozyme in hamster pancreas and pancreatic carcinoma cell lines.

Cellular differentiation and proliferation are dependent upon phosphorylation by endogenous protein kinase C (PKC) isozymes in many cell types. Western blotting with a C-terminally directed rabbit polyclonal anti-PKC zeta antibody detected a doublet of approximately 81 kDa in normal hamster pancreatic tissue and hamster pancreatic carcinoma (PC-1) and human pancreatic carcinoma (PANC-1) cells. Preabsorption of the antibody with the specific peptide blocked the appearance of the 81-kDa band, indicating that the band was specifically recognized by the PKC zeta antibody. In contrast, antibodies for PKC alpha, beta, gamma, delta, and epsilon failed to show specific immunoreactivity for normal pancreatic tissue or PANC-1 or PC-1 cells. Immunocytochemical analysis identified PKC zeta in the cytoplasm of ductules and large ducts, to a lesser extent in the islets of the hamster pancreas, and in the normal cultured pancreatic duct epithelial cells and pancreatic carcinoma (PANC-1 and PC-1) cell lines. Specific reactivity was seen by electron microscopy in the ductal cells of the normal pancreatic tissue. In normal pancreatic ductal tissue and primary pancreatic ductal hyperplasia and carcinoma, the proportional labeling of PKC zeta in nuclei and cytoplasm was similar. Our results demonstrating the presence of PKC zeta isozyme in the normal pancreas, cultured normal pancreatic duct epithelial cells, and pancreatic carcinoma cells or carcinoma tissue suggests a role for this isozyme in the normal physiology of the pancreas and perhaps in pancreatic carcinoma.