Protein kinase C activity in normal and neoplastic squamous epithelia from the upper aero-digestive tract

In the present study the protein kinase activity was determined in surgical specimens of squamous cell carcinoma from the upper aero-digestive tract, and the activity was compared with the activity in normal mucosa obtained from the same location in patients undergoing surgery for non-neoplastic diseases. The basal protein kinase activity in the soluble fraction was about 15-fold higher in tumors as compared to in normal mucosa. The difference between protein kinase activity in the presence of Ca2+ and presence/absence of phosphatidylserine/diolein was taken as the activity of protein kinase C. Protein kinase C activity in the presence of 0.5 mM Ca2+ was 10.0 +/- 2.1 pmol 32P/mg prot. x min in tumors (n = 19) and 2.4 +/- 0.7 pmol 32P/mg prot. x min. in normal mucosa (n = 6). A similar difference was obtained with 1 mM Ca2+. An even greater difference in protein kinase C activity was seen when the soluble enzyme had been partially purified by ion-exchange chromatography on DE-52 columns. In this case a 7-fold higher protein kinase activity was found in tumors as compared to in normal mucosa. In the particulate fraction the basal protein kinase activity was about 3-fold higher in tumors as compared to in normal mucosa. Protein kinase C activity in the particulate fraction, defined as described above, was 10.7 +/- 4.1 pmol 32P/mg prot. x min in tumors and 6.1 +/- 4.4 pmol 32P/mg prot. x min in normal mucosa. These results show a significantly higher activity in both total protein kinase activity and protein kinase C activity in epithelial tumors from the upper aero-digestive tract.(ABSTRACT TRUNCATED AT 250 WORDS)