This observation indicates that 5-FU has not been excluded by efflux and is able to enter the nuclei of the cancer cells and complex with TYMS in the 5-FU resistant cells, and also that the upregulation of TYMS associated with FOXM1 overexpression in the resistant colon carcinoma cells plays a predominant role in mediating 5-FU insensitivity through upregulation of the drug targets. This evidence concerns the gene TYMS and colon carcinoma.