DNA Microsatellite Instability and Mismatch Repair Germ Line Mutation in Iranian Patients with Hereditary non-Polyposis Colorectal Cancer

HNPCC (hereditary non-polyposis colorectal cancer) is the most common type of hereditary colorectal cancers. Germ line mutations in different DNA mismatch repair genes (MMR) and microsatellite instability (MSI) are associated with HNPCC. But still there has not been any report from Iran. The purpose of this study is to evaluate MSI and MMR gene mutation among a group of Iranian patients with the clinical diagnosis of HNPCC. In this cross-sectional study 94 patients (m/f=1.41) who fulfilled at least on of the Bethesda criteria were assessed. MSI analysis was performed in all cases. SSCP was used as screening test in all cases to select highly probable MMR mutation for DNA sequencing. Information analyzed by Chi2, Fisher exact, independent t-test with SPSS16 and EPI6 soft wares. MSI analysis shows 41.5% MSI-H, 17% MSI-L, and 41.5% MSS in this study. There were 18 (19.1%) band shift in SSCP results, which was include 8 mutations after DNA sequencing. ‍ The pattern of MMR mutations in Iranian patients differs from the reports of other countries. The evaluation of the histopathology and clinical features of colorectal cancer burdens in Iran and also the frequency additional HNPCC genes remain as a point of concern.