Type I and II cyclic adenosine 3':5'-monophosphate-dependent protein kinase in human gastric mucosa and carcinomas

Cyclic adenosine 3':5'-monophosphate (cAMP)-dependent and cAMP-independent protein kinase activity and the isoenzyme pattern of cAMP-dependent protein kinase were compared in tissues from human nonneoplastic gastric mucosa, 11 human gastric carcinomas, and 2 xenotransplantable human gastric carcinomas (SC-6-JCK and St-15). No difference in total protein kinase activity could be observed between nonneoplastic gastric mucosa and gastric carcinomas. According to diethylaminoethyl cellulose column chromatography, the isoenzyme pattern of the nonneoplastic gastric mucosa was the same in both the gastric fundus and the antrum, and the activity ratio of type II to type I was 5.01. In gastric carcinomas, the elevation of type I was detected independently of the histological type. In xenotransplantable human gastric carcinomas in nude mice, type I isoenzyme was significantly elevated. The activity ratio of type II to type I was 1.70 in SC-6-JCK carcinomas and 1.81 in St-15 carcinomas, respectively. These results suggest that type I cAMP-dependent protein kinase activity in the stomach may be a biochemical marker for malignant transformation and transplantability of gastric tumors.