High Rate of Mutation in Mitochondrial DNA Displacement Loop Region in Human Colorectal Cancer

Abstract

Mitochondrial DNA mutations are found in many kinds of human cancer and the 1.1 kb displacement loop region has been identified as a "hot spot" for mutation in mitochondrial DNA of tumors. This study evaluated the mutation frequencies in hypervariable regions of mitochondrial displacement loop in patients with colorectal cancer. We examined the frequency of mutations in the mitochondrial DNA displacement loop region of 40 colorectal cancer samples in comparison to 150 samples from people without any type of familial cancer history, by automated DNA sequencing. Alignment was made with the revised Cambridge Reference Sequence and any differences recorded as single base substitution, insertions, and deletions. Our results showed that the rate of displacement loop variations was higher in colorectal cancer patients than controls. Nineteen single nucleotide polymorphisms were found; among them eighteen occurred in the displacement loop region. Mutations in mtDNA D-loop region probably do not cause colorectal cancer but are more likely to be epiphenomena; patients with the high mtDNA variants are at a higher risk of colorectal cancer.