Furthermore, the abundance of TS mRNA or protein seems to be higher in squamous cell carcinoma than in other histotypes of NSCLC (Ceppi et al, 2006; Monica et al, 2009; Takezawa et al, 2010), and high levels of TS expression in various tumour types have been suggested to correlate with a poor response to TS-targeted agents (Johnston et al, 1994, 1997; Pestalozzi et al, 1997; Ferguson et al, 1999). This evidence concerns the gene TYMS and squamous cell carcinoma.