An original phylogenetic approach identified mitochondrial haplogroup T1a1 as inversely associated with breast cancer risk in BRCA2 mutation carriers.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files. This article is open access.Individuals carrying pathogenic mutations in the BRCA1 and BRCA2 genes have a high lifetime risk of breast cancer. BRCA1 and BRCA2 are involved in DNA double-strand break repair, DNA alterations that can be caused by exposure to reactive oxygen species, a main source of which are mitochondria. Mitochondrial genome variations affect electron transport chain efficiency and reactive oxygen species production. Individuals with different mitochondrial haplogroups differ in their metabolism and sensitivity to oxidative stress. Variability in mitochondrial genetic background can alter reactive oxygen species production, leading to cancer risk. In the present study, we tested the hypothesis that mitochondrial haplogroups modify breast cancer risk in BRCA1/2 mutation carriers.We genotyped 22,214 (11,421 affected, 10,793 unaffected) mutation carriers belonging to the Consortium of Investigators of Modifiers of BRCA1/2 for 129 mitochondrial polymorphisms using the iCOGS array. Haplogroup inference and association detection were performed using a phylogenetic approach. ALTree was applied to explore the reference mitochondrial evolutionary tree and detect subclades enriched in affected or unaffected individuals.We discovered that subclade T1a1 was depleted in affected BRCA2 mutation carriers compared with the rest of clade T (hazard ratio (HR) = 0.55; 95% confidence interval (CI), 0.34 to 0.88; P = 0.01). Compared with the most frequent haplogroup in the general population (that is, H and T clades), the T1a1 haplogroup has a HR of 0.62 (95% CI, 0.40 to 0.95; P = 0.03). We also identified three potential susceptibility loci, including G13708A/rs28359178, which has demonstrated an inverse association with familial breast cancer risk.This study illustrates how original approaches such as the phylogeny-based method we used can empower classical molecular epidemiological studies aimed at identifying association or risk modification effects.European Commission Seventh Framework Program 223175: HEALTH-F2-2009-223175 Cancer Research UK C12292/A11174 C1287/A10118 C1287/A11990 C5047/A8385 National Health and Medical Research Council (NHMRC) program National Health and Medical Research Council (NHMRC) American Cancer Society Early Detection Professorship SIOP-06-258-01-COUN Intramural Research Program of the National Cancer Institute, National Institutes of Health National Cancer Institute, National Institutes of Health UM1 CA164920 Lithuania (BFBOCC-LT): Research Council of Lithuania LIG-07/2012 LSC 10.0010.08 European Social Fund 2009/0220/1DP/1.1.1.2.0/09/APIA/VIAA/016 Liepaja City Council, Liepaja, Latvia Breast Cancer Research Foundation Cancer Association of South Africa (CANSA) Morris and Horowitz Families Professorship in Cancer Etiology and Outcomes Research NEYE Foundation Spanish Association against Cancer (Asociacion Espanola Contra el Cancer) AECC08 Thematic Network Cooperative Research in Cancer (Red Tematica Investigacion Cooperativa en Cancer (RTICC), Centro de Investigacion Cancer, Salamanca, Spain) RTICC 06/0020/1060 Spanish Ministry of Science and Innovation FIS PI08 1120 Fondo de Investigacion Sanitaria (FIS) SAF2010-20493 Fundacion Mutua Madrilena (FMMA) City of Hope Clinical Cancer Genetics Community Network and the Hereditary Cancer Research Registry (COH-CCGCRN) National Cancer Institute and the Office of the Director, National Institutes of Health RC4CA153828 Italian citizens Fondazione IRCCS Istituto Nazionale Tumori Italian Association for Cancer Research (AIRC) European Union (European Social Fund (ESF) Greek national funds through the "Education and Lifelong Learning" operational program of the National Strategic Reference Framework (NSRF) - Research Funding Program of the General Secretariat for Research and Technology: ARISTEIA "Heracleitus II: Investing in knowledge society through the European Social Fund" Deutsches Krebsforschungszentrum (DKFZ) National Institute for Health Research (NIHR) grant to the Biomedical Research Centre, Manchester, UK NIHR grant to the Biomedical Research Centre at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London University of Kansas Cancer Center P30 CA168524 Kansas Bioscience Authority Eminent Scholar Program Chancellors Distinguished Chair in Biomedical Sciences Professorship German Cancer Aid 109076 Center for Molecular Medicine Cologne (CMMC) Ligue National Contre le Cancer Association "Le cancer du sein, parlons-en!" Award Canadian Institutes of Health Research for the CIHR Team in Familial Risks of Breast Cancer program GOA BOF10/GOA/019 Ghent University Hospital National Cancer Institute grants to the GOG Administrative Office and Tissue Bank CA 27469 GOG Statistical and Data Center CA 37517 GOG's Cancer Prevention and Control Committee CA 101165 Instituto de Salud Carlos III (ISCIII), Madrid, Spain RD12/00369/0006 12/00539 European Regional Development Fund (Fonds europeen de developpement regional (FEDER)) funds Helsinki University Central Hospital Research Fund Academy of Finland 266528 Finnish Cancer Society Sigrid Juselius Foundation Dutch Cancer Society NKI1998-1854 NKI2004-3088 NKI2007-3756 Netherlands Organization of Scientific Research NWO 91109024 Pink Ribbon grant 110005 Biobanking and Molecular Resource Infrastructure (BBMRI) NWO 184.021.007/CP46 Hungarian Research and Technological Innovation Fund (KTIA)/Hungarian Scientific Research Fund (Orszagos Tudomanyos Kutatasi Alapprogramok (OTKA)) KTIA-OTKA CK-80745 KTIA-OTKA K-112228 Institut Catala d'Oncologia (ICO): contract grant sponsor: Asociacion Espanola Contra el Cancer Spanish Health Research Foundation Ramon Areces Foundation Instituto de Salud Carlos III (ISCIII) Catalan Health Institute Autonomous Government of Catalonia International Hereditary Cancer Center (Department of Genetics and Pathology, Pomeranian Medical University, Szczecin, Poland) PBZ_KBN_122/P05/2004 Icelandic Association "Walking for Breast Cancer Research" Landspitali University Hospital Research Fund Canadian Institutes of Health Research (CIHR) for the "CIHR Team in Familial Risks of Breast Cancer" program, Canadian Breast Cancer Research Alliance 019511 Ministry of Economic Development, Innovation and Export Trade PSR-SIIRI-701 Ministero della Salute and a "5 x 1,000" Istituto Oncologico Veneto grant Liga Portuguesa Contra o Cancro National Breast Cancer Foundation Queensland Cancer Fund Cancer Councils of New South Wales, Victoria, Tasmania and South Australia Cancer Foundation of Western Australia National Institutes of Health (NIH) through the National Cancer Institute (NCI) CA 116167 CA 128978 CA 176785 NCI Specialized Program of Research Excellence (SPORE) in Breast Cancer CA116201 US Department of Defense Ovarian Cancer Idea award W81XWH-10-1-0341 Ministry of Health of the Czech Republic to Masaryk Memorial Cancer Institute MMCI 00209805 European Regional Development Fund State Budget of the Czech Republic (RECAMO) CZ. 1.05/2.1.00/03.0101 Charles University in Prague project UNCE204024 Robert and Kate Niehaus Clinical Cancer Genetics Initiative Intramural Research Program of the National Cancer Institute Westat, Inc, Rockville, MD, USA N02-CP-11019-50 N02-CP-65504 Clalit Health Services in Israel Israel Cancer Association Breast Cancer Research Foundation (BCRF), New York, NY, USA Russian Federation for Basic Research 11-04-00227 12-04-00928 12-04-01490 Federal Agency for Science and Innovations, Russia 02.740.11.0780 Ohio State University Comprehensive Cancer Center Istituto Toscano Tumori (ITT) Israeli Inherited Breast Cancer Consortium Swedish Breast Cancer Swedish Cancer Society Ralph and Marion Falk Medical Research Trust Entertainment Industry Fund National Women's Cancer Research Alliance University of California, Los Angeles Jonsson Comprehensive Cancer Center Foundation: Breast Cancer Research Foundation University of California, San Francisco Cancer Risk Program and Helen Diller Family Comprehensive Cancer Center Cancer Research UK University of Pennsylvania: National Institutes of Health (NIH) R01 CA102776 R01 CA083855 Susan G Komen for the Cure, Basser Center for BRCA Victorian Familial Cancer Trials Group (VFCTG): Victorian Cancer Agency, Cancer Australia, National Breast Cancer Foundation 5U01 CA113916 R01 CA140323 ISCIIIRETIC RD06/0020/1051 PI09/02483 PI10/01422 PI10/00748 PI13/00285 PI13/00189 2009SGR290 PI13/00189 2009SGR283 CA125183 R01 CA142996 1U01CA16103