Previous in vitro studies have shown that TS expression correlated with objective response of NSCLC treated with pemetrexed-containg chenmotherapy Ozasa et al. [15] documented that the expression level of the TS gene was significantly correlated with the concentration of pemetrexed for 50% cell survival (IC50) in 11 non-small cell lung cancer cell lines, suggesting up-regulation of the expression of the TS gene may have an important role in the acquired resistance to pemetrexed. This evidence concerns the gene TYMS and non-small cell lung carcinoma.