ORIGINAL ARTICLE Mitochondrial complex I and V gene polymorphisms associated with breast cancer in mizo-mongloid population Sunaina Thapa 1 • Freda Lalrohlui 1 • Souvik Ghatak 1 • John Zohmingthanga 2 • Doris Lallawmzuali 3 • Jeremy L. Pautu 3 • Nachimuthu Senthil Kumar 1 Received: 29 January 2015 / Accepted: 7 April 2015 Ó The Japanese Breast Cancer Society 2015 Abstract Background Mizoram has the highest incidence of cancer in India. Among women, breast cancer is most prevalent and the state occupies fifth position globally. The reason for high rate of cancer in this region is still not known but it may be related to ethnic/racial variations or lifestyle factors. Methods The present study aims to identify the candidate mitochondrial DNA (mtDNA) biomarkers—ND1and ATPase for early breast cancer diagnosis in Mizo popula- tion. Genomic DNA was extracted from blood samples of 30 unrelated breast cancer and ten healthy women. The mtNDI and mtATP coding regions were amplified by step- down PCR and were subjected to restriction enzyme di- gestion and direct sequencing by Sanger method. Subse- quently, the results of the DNA sequence analysis were compared with that of the revised Cambridge Reference Sequence (rCRS) using Mutation Surveyor and MITOMAP. Results Most of the mutations were reported and new mutations that are not reported in relationship with breast cancer were also found. The mutations are mostly base substitutions. The effect of non-synonymous substitutions on the amino acid sequence was determined using the PolyPhen-2 software. Statistical analysis was performed for both cases and controls. Odds ratios (ORs) and 95 % confidence intervals (CIs) were estimated from logistic regression. High intake of animal fat and age at menarche was found to be associated with a higher risk of breast cancer in Mizo population. Conclusion Our results also showed that ATPase6 as compared to ATPase8 gene is far more predisposed to variations in Mizo population with breast cancer and this finding may play an important role in breast cancer prognosis. Keywords mtDNA Á ATP6 Á ND1 Á ATP8 Á OXPHOS Á Breast cancer Introduction Mizoram is the southernmost state in the northeast, sharing its borders with Tripura, Assam, and Manipur along with Myanmar and Bangladesh. The Mizo people are believed to be a part of the Mongoloid race and Mizoram has the highest number of tribal people among all states of India. According to the National Cancer Registry Program 2010, Mizoram has the highest incidence of cancer in India. Among women, breast and cervix cancer are most preva- lent and the state occupies fifth position globally [1]. Breast cancer is a type of cancer which originates from breast tissues and is a heterogeneous disease with a variety of subtypes, with distinct gene expression profiles, that have substantial implications for prognosis and survival rates [2]. Most of the breast cancers are like some solid tumors, approximately 25–30 % are found in familial Electronic supplementary material The online version of this article (doi:10.1007/s12282-015-0611-1) contains supplementary material, which is available to authorized users. & Nachimuthu Senthil Kumar nskmzu@gmail.com 1 Department of Biotechnology, Mizoram University, Aizawl 796004, Mizoram, India 2 Department of Pathology, Civil Hospital, Aizawl 796001, Mizoram, India 3 Mizoram State Cancer Institute, Zemabawk, Aizawl 796017, Mizoram, India 123 Breast Cancer DOI 10.1007/s12282-015-0611-1