Molecular Analyses Reveal Novel Mutations in Mitochondrial DNA D-loop Region of Breast Cancer Patients

Abstract

D-Loop or displacement loop region is a triple-stranded section found in the noncoding region of the mitochondrial DNA (mtDNA) that contains important transcription and replication components of mtDNA. D- Loop is composed of 1121 base pairs which are highly venerable to mutations. This study aims to investigate D-loop mutations in females who had breast cancer and compare them with the global sequence of D-loop in healthy individuals. Forty tissue samples were taken included 21 samples were malignant cancer and 19 samples were benign cancer (control group). The mtDNA was extracted using a gSYNCTM DNA extraction kit, and a 558bp fragment of the noncoding region within D-loop section was amplified by PCR. After purification of the PCR products, amplicons were sequenced via sanger sequence. The sequence results were analyzed using Bioedite software (ver.7.7.1) to identify mutations. This study focused on extracting and analyzing the D-Loop region of mitochondrial DNA (mtDNA) from female breast cancer patients. We employed PCR and Sanger sequencing methods to explore mutations within this region. Our findings revealed a total of 18 mutations, including InsG58, G64A, C185T, T16317C, T16343C, A16352G, G16355A, A16359G, and DL/T16480,

which, to our knowledge, have not been previously reported in Iraqi patients. Notably, all identified mutations were located within the hypervariable regions 1 and 2 (HV1 and HV2) of the D-Loop. Substitution mutations were the most prevalent among the mutations observed, suggesting that alterations in the D-Loop region may significantly contribute to the development of breast cancer.