The gene polymorphism of MTHFR was found to be associated with the efficacy of pemetrexed therapy in patients with NSCLC (34), and 677C > T SNP in the MTHFR gene can lead to reduced expression of MTHFR as well as lowered levels of 5-methylTHF, resulting in the enhanced activity of TS and the decreased therapeutic effect of pemetrexed (35). The gene discussed is MTHFR; the disease is non-small cell lung carcinoma.