Pyrimidine nucleotide synthesis is more extensive in poorly differentiated than in well-differentiated human gastric carcinoma.

In tissues obtained from patients undergoing gastrectomy, the activities of 12 enzymes involved in pyrimidine nucleotide synthesis: cytidine triphosphate (CTP) synthetase, deoxycytidine monophosphate (dCMP) deaminase, thymidine monophosphate (dTMP) kinase, uridine (Urd), deoxycytidine (dCyd) and thymidine (dThd) kinases, Urd, deoxyuridine (dUrd) and dThd phosphorylases, cytidine (Cyd) and dCyd deaminases, and DNA polymerase were examined in the eight-well-differentiated and 12 poorly differentiated gastric cancer tissues and the ten normal tissues. These cases were clinically advanced and serosal invasions were evident. Activities of these enzymes were higher in the poorly differentiated tissues than the well differentiated type and in the normal tissues. Significant differences were noted between the poorly differentiated and well-differentiated types, in dTMP kinase (P less than 0.02), dThd kinase (P less than 0.05), dThd phosphorylase (P less than 0.01), and DNA polymerase (P less than 0.05). The authors' findings show that the level of pyrimidine nucleotide synthesis, in both de novo and salvage pathways, is higher in the poorly differentiated gastric cancer tissues than in the well-differentiated type and suggest that antitumor drugs have an increased susceptibility in cases of poorly differentiated gastric carcinoma.