{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Thymidylate synthase (TS) catalyzes the methylation of deoxyuridine monophosphate to deoxythymidine monophosphate using 5, 10-methylenetetrahydrofolate as a cofactor. This enzyme is critical for DNA repair and replication. Polymorphism of the gene TYMS, which encodes TS, may be associated with etiology of neoplasia and responses to chemotherapy. TS inhibitors like 5-fluorouracil have been successful in down-regulating tumor progression and increasing immune responses in pancreatic, breast, gastric, ovarian, lung, and head & neck cancer. Variability of TS protein expression and gene copy number may indicate potential benefit from protein expression pemetrexed therapy in selected SCC patients."}]}]}