Carbamyl phosphate synthetase I. A novel marker for gastric carcinoma.

Carbamyl phosphate synthetase I (CPS1) is an initial enzyme of urea synthetase system. It exists exclusively in liver cells and epithelial cells of the small intestine. By immunocytochemistry, 70.5% of 88 surgically resected gastric carcinomas (42 advanced and 46 early gastric carcinomas) was found to be CPS1 immunoreaction positive, whereas all other carcinomas (of the esophagus, colon, pancreas, lung, breast, ovary, kidney, prostate and urinary bladder) tested were negative. CPS1 expression in gastric carcinoma was closely related to the types of mucin secreted by the carcinoma cells. Most carcinomas secreting sialomucin were CPS1 positive, yet those secreting sulfomucin or neutral mucin did not express CPS1. The types of intestinal metaplasia adjacent to the carcinoma correlated neither with CPS1 expression nor with the histological types of carcinoma. Owing to the fact that gastric carcinomas with CPS1 expression possess the characteristics of small intestinal epithelium, it is very likely that CPS1 can be used as a novel marker for gastric carcinoma originating from complete type intestinal metaplasia.