Another predictor that has been suggested is tumour tissue expression level of mRNA or protein of 5-FU metabolic pathway genes, such as thymidylate synthase, orotate phosphoribosyltransferase, and thymidine phosphorylase (Ichikawa et al, 2006; Choi et al, 2010; Koizumi et al 2010). This evidence concerns the gene TYMP and neoplasm.