To assess the MutT-related gene expression as a whole, we determined levels of mRNA for MTH1, MTH2, MTH3 and NUDT5 in six kinds of human CRC cell lines (HCT116, SW480, SW620, LoVo, COLO320 and T84) and the human normal intestinal mucous cell line CCC-HIE-2 by performing quantitative real-time PCR (qRT-PCR). Here, NUDT18 is linked to colorectal carcinoma.