In a 5-FU resistant cell line, UMPS down-regulation was identified [135], whereas experimental overexpression of UMPS increased toxicity of 5-FU in vitro [290,291], and the ratio of UMPS-to-DPD expression has been associated with better overall survival in a Japanese cohort of 5-FU-treated patients with colorectal cancer [292]. This evidence concerns the gene UMPS and colorectal cancer.