Protein kinase C activity as a potential marker for colorectal neoplasia.

Protein kinase C (PKC) is a mediator of transmembrane signal transduction, important in cell growth and differentiation. Cell activation by extracellular signals is associated with a translocation of PKC from the cytosol to the membrane. We measured and compared PKC activity in cytosol and membrane fractions of normal and neoplastic colorectal tissue. Total and membrane-associated PKC activity in normal colorectal tissue was greater in patients (N = 16) with colorectal cancer compared to that from patients with a normal colonoscopy (N = 16), P < 0.01. A similar trend was noted in PKC activity of normal colorectal tissue from patients with adenomas compared to patients with a normal colonoscopy. PKC activity (total, membrane-associated, percent membrane) was not different in neoplastic colorectal tissue compared to that of adjacent normal tissue. However, there was a considerable range of PKC activity noted in all groups, which would limit the utility of PKC activity as a marker for colorectal neoplasia.