Increased activities of thymidine kinase isozymes in human colon polyp and carcinoma

Thymidine kinase (TK), the enzyme in the pyrimidine salvagepathway, and its isozymes were examined in 15 specimens of normalmucosa, 14 polyps and 14 carcinomas in human colon. The averageTK activities in colon polyps and carcinomas were about 1.6and 2.9 times that in normal colon mucosa, respectively. Thecolon TK isozymes were separated into 2 types by DEAE-cellulosecolumn chromatography. The activity of the TK isozyme elutedwith 0.1 M NaCI in buffer was 1.6-fold higher in colon polypand 1.5-fold higher in colon carcinoma than that in normal colonmucosa. In colon carcinoma, but not colon polyp, the activityof the other isozyme eluted with buffer alone was increasedto 5.1-fold that in normal tissues. As the activity of the latterisozyme was not affected by deoxycytidine triphosphate, it maybe involved in DNA replication. The results suggest that increasesin the activities in the former and latter TK isozymes may indicatetumorigenesis and carcinogenesis, respectively, in the humancolon.