In addition, long-term treatment with 5FU leads to increased expression of thymidylate synthase (TS), Bcl-1, Bcl-XL and Mcl-1 as well as increased activity of deoxyuridine triphosphatase and methylation of MLH1, which are associated with 5FU resistant colon cancers (reviewed in 68). This evidence concerns the gene DUT and malignant colon neoplasm.