Enzyme activity and protein patterns as premalignant markers in mucosal biopsy specimens from the large intestine

Total enzyme activity of glucose-6-phosphate dehydrogenase (G6PD) and lactate dehydrogenase (LD) was measured in homogenates of resected biopsy specimens and in endoscopic biopsy specimens. LD isoenzyme patterns were scanned by a laser technique after agarose gel electrophoresis. Examinations were performed in homogenates of premalignant lesions such as ulcerative colitis and adenomas of the colon, with normal mucosa and carcinomas as control material. Additionally, two-dimensional electrophoretic protein patterns were compared for normal mucosa, adenomas, and carcinomas of the large intestine. The mean activity of both G6PD and LD was highest in the presence of dysplasia; however, only G6PD activity seemed independent of inflammatory changes. The percentage of LD isoenzyme M monomers was significantly higher in homogenates of specimens with dysplastic changes than in specimens with only inflammatory changes. A positive correlation was found between total LD isoenzyme M monomers and LD 5 monomers for the whole material and for each of the histological subgroups of ulcerative colitis. A positive correlation between total LD activity and the percentage of LD 5 monomers was seen only for dysplastic, adenomatous, and malignant tissues. The several hundred protein spots seen on two-dimensional protein maps showed that most of the spots were common for normal mucosa, adenomas, and carcinomas, but differences were also seen. Polyps and carcinomas had strikingly similar protein patterns, different from that of normal mucosa. The results of the two-dimensional protein electrophoresis lend further support to the hypothesis that polyps are precursors of carcinomas of the large intestine.(ABSTRACT TRUNCATED AT 250 WORDS)