DPYD and neoplasm: Docetaxel regulates the expression of enzymes involved in fluorouracil metabolism, which are thymidine synthase, dihydropyrimidine dehydrogenase, and rotary phosphotransferase, showing synergistic anti-tumor effects with fluorouracil, especially S-1 (Maeda, et al., 2004; Takahashi, et al., 2005; Wada, et al., 2006).