Enzymatic characteristics of tubular adenomas and carcinomas of the large intestine.

Enzymes activities in homogenates of the large intestine were measured in biopsies from 11 tubular adenomas and six carcinomas and from the corresponding normal mucosa of each individual. A similar and significant increase was found in the total activities of glucose-6-phosphate dehydrogenase (G 6 PD), pyruvate kinase, and lactate dehydrogenase in adenomas and carcinomas as compared with the levels of normal mucosa. The lactate dehydrogenase isoenzyme patterns showed also a marked and similar change in the adenomas and carcinomas with a significant increase of lactate dehydrogenase M-monomers. Most of the adenomas showed slight to moderate dysplasia. The results indicate that the measurement of total G 6 PD, pyruvate kinase and lactate dehydrogenase activities for screening purposes has no predictive value in separating non-premalignant from premalignant adenomas. Moreover, it seems that the enzymatic characteristics of malignancy are present even in tubular adenomas. This is in agreement with the theory of a polyp-cancer sequence.