DPYD and neoplasm: In conclusion, although other enzymes such as dihydropyrimidine dehydrogenase, which regulate the rate limiting step in the catabolism of 5-FU as well as the disregulation in tumour cells of critical pathways regulating survival, growth arrest or apoptosis, could be related to the antitumour efficacy of fluoropyrimidines (Ishikawa et al, 1999; Yen and McLeod, 2007) our results indicate that vorinostat has the unique capability to modulate not only TS but also TP expression in tumour cells (Figure 6C) and, consequently, can synergise with capecitabine.