Abstract: BACKGROUND AND AIM：To investigate the association between the MYH(MutY homologue)genovariation and colorectal cancer risk. MATERIALS AND METHODS： Denaturing high performance liquid chromatography (DHPLC)and DNA sequencing were used to delineate the variants in 7 of 16 exon-districts in the 140 colorectal cancer patients and 280 controls. All data was analyzed by SPSS software. RESULTS：Four genovariation sites, Exon1-316 G>A, Exon1-292 G>A and Intron1＋11 C>T, in exon 1 district were detected in all variants of cases and controls simultaneouly. The variation frequency in cases was significantly higher than that in controls, genovariation risk in cases was 8.16-fold more than controls(P=0.04；OR=8.16，95％ CI=1.01～203.70). A missense variation, Exon14＋74 T>A, p.V463E, was found in exon 14. A deletion variation, nt 1678-80 del GTT, was found in exon 16. In cases, the rectal cancer genovariation frequency was higher than colon cancer, variation risk in the former was 7.18-fold more than the latter(P=0.04；OR=7.18，95％ CI=1.102～165). CONCLUSION： MYH variation may function as a risk factor for colorectal cancer development. Most patients had rectal cancer. Similar to other Asian races, the MYH variant frequency in Chinese is lower than Caucasian.No variant is found in and around Exon 7 which is one of the most frequently mutated exons in Caucasians. This indicates that the differences of MYH variants may be related to racial differences.

Key words: MYH/MutY homologue, MAP, variation, sporadic colorectal cancer