Pemetrexed is a synthetic multi-target antifolate and contains pyrrolidine grouping in structure, which can effectively inhibit dihydrofolate reductase, glycinamide ribonucleotide formyl transferase and thymidylate synthase and block thymidine and purine synthesis, thus affecting nucleic acid synthesis in tumor cells to exert anti-tumor effects (17). This evidence concerns the gene DHFR and neoplasm.