MRC1 and colonic neoplasm: 5-iododeoxyuridine is one of the representatives of halogenated pyrimidine compounds, in an athymic nude mice human colon cancer xenograft model, the SER ranged from 1.20–1.48 in HCT116(MMR-) tumor xenografts and HCT116/3-6(MMR+) tumor xenografts while getting 2Gy or 4Gy irradiation.