Identification of a novel mutation associated with familial adenomatous polyposis and colorectal cancer.

Colorectal cancer (CRC) is among the most fatal forms of solid tumor in men and women. While the majority of diagnosed CRC cases are sporadic, 15‑25% of patients have a family history of adenomatous polyposis and CRC; however, the associated gene mutations remain largely unidentified. The aim of the present study was to investigate the genomes of a four‑generational Chinese Han family with familial adenomatous polyposis and CRC to identify the potential genetic anomalies associated with the disease. Diagnoses were made by physical and enteroscopic examinations of all the family members. Mutational analyses of the potential CRC‑associated genes were carried out by direct gene sequencing, and the statistically significant differences in polymorphisms between normal and diseased populations were determined. Multiple sequence alignment and protein modeling were conducted using the Vector NTI and DNAMAN software tools. Clinical and pathological features of all the examined patients were consistent with typical familial adenomatous polyposis (FAP) syndrome. From the genomes of these family members, a 131564T>C (p.1125Val>Ala) mutation was identified in exon 15 of the APC gene, and a 1126G>C (p.324Gln>His) mutation was identified in exon 12 of the MUTYH gene. The 131564T>C mutation co‑segregated with the affected individuals in the family and was specifically associated with the incidence of CRC (P=0.018<0.05). The 1125Val residue was highly conserved in the APC protein, and the p.1125Val>Ala mutation led to changes in the secondary structure and hydrophilicity of the APC protein. In conclusion, the APC gene mutation 131564T>C is associated with FAP and the pathogenesis of CRC.