Analysis of mitochondrial ND1 gene in human colorectal cancer

BACKGROUND Colorectal cancer as a mortal disease affected both sexes of all ethnic and racial human groups. Former studies have indicated some mutations in the mitochondrial DNA (mtDNA) in different human cancers. Complex I NADH has the most subunits encoded by mtDNA. For a better understanding of the mtDNA abnormality in colorectal cancer some genes of this complex is screened for existence of mutations. METHODS One of the main regions of the mtDNA encoding protein was screened by PCR-RFLP followed by DNA sequencing. The obtained sequences were aligned with the revised Cambridge Reference Sequence (rCRS). Each alteration recorded as single nucleotide polymorphisms (SNPs), deletions or insertions. RESULTS Eight mutations were found in 15 samples out of 30 studied populations and no mutation detected in other 15 samples. Among these 15 mutated samples, 7 different mutations were found in 7 patients, that means one mutation per patient and the 8th mutation (T4216C) was common in the rest of 8 samples; in other words T4216C mutation in 27% of tested samples was identified (8 patients out of 30 patients). The existence of T4216C mutation was found to be significantly different (p ≤ 0.05) between tumoral patient's tissue and adjacent normal tissue. CONCLUSIONS Results showed that a high frequency of somatic alterations of mtDNA occurs during the carcinogenesis and/or the progression of colorectal cancer. Based on the mtDNA mutation pattern observed in this study and other previously studies it is believed that looking for somatic mutations in mtDNA would be one of the diagnostic values in early detection of cancer.