TS expression is significantly higher in squamous cell carcinoma than in adenocarcinoma [13], and multiple cell-line studies suggest that high TS expression is associated with reduced sensitivity to pemetrexed [14,15]; although this has not been validated clinically, it may partly explain the superior efficacy of pemetrexed in nonsquamous versus squamous NSCLC [16]. The gene discussed is TYMS; the disease is squamous cell carcinoma.