Investigating the prevalence of point mutations in the human mutL homolog 1 gene in colorectal cancer patients in the Northwest of Iran

Abstract

Background/aims: Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common form of colorectal cancer (CRC) syndrome, in which the mutations in mismatch repair genes have been implicated in the disease etiopathogenesis. The aim of this study was to investigate the prevalence of human mutL homolog 1 (hMLH1) gene point mutations in patients with HNPCC in Northwest of Iran. Methodology: In this study, 30 patients with HNPCC were selected who fulfilled the Amsterdam II criteria. Moreover, 30 subjects were selected as the control group. Total RNA was extracted from peripheral blood sample, and complementary DNA (cDNA) was synthesized using specific primers. Screening of germline mutations within the hMLH1 gene was performed by direct cDNA sequencing. Functional evaluation was conducted through real-time polymerase chain reaction mRNA expression using the TaqMan Gene Expression Assay. Results: In this study, c.655A >G polymorphism was found in 13.3% of patients and 10% of the control group, while c.1959G > T polymorphism was found in only one of the patients. Two novel variants, including c.973C > A and c.1086C > A, were found in 13.3% and 20% of patients, respectively, that were identified for the 1 st time in this study. Moreover, the mRNA expression of hMLH1 gene in patients carrying the c.973C > A and c.1086C > A mutations showed no statistically significant difference in comparison to patients with no mutation and healthy controls. Conclusions: This study establishes that the frequency and type of mutations do not follow a similar pattern in other populations due to genetic and geographical differences.