TYMS and neoplasm: It is also known that pemetrexed and 5-FU can inhibit DNA biosynthesis processes by suppressing the activity of TS, an enzyme that catalyzes the transformation of deoxyuridine monophosphate to deoxythymidine monophosphate for the maintenance of DNA replication and repair, thereby inducing DNA damage in tumor cells through TS inhibition.17 39 Although there is no evidence showing TS being involved in gene regulation, we tried to evaluate the possibility that TS might be the direct target of pemetrexed for regulating PD-L1 gene expression.