title: Mitochondrial DNA copy number is associated with breast cancer risk.
abstract: Mitochondrial DNA (mtDNA) copy number in peripheral blood is associated with increased risk of several cancers. However, data from prospective studies on mtDNA copy number and breast cancer risk are lacking. We evaluated the association between mtDNA copy number in peripheral blood and breast cancer risk in a nested case-control study of 183 breast cancer cases with pre-diagnostic blood samples and 529 individually matched controls among participants of the Singapore Chinese Health Study. The mtDNA copy number was measured using real time PCR. Conditional logistic regression analyses showed that there was an overall positive association between mtDNA copy number and breast cancer risk (P(trend) = 0.01). The elevated risk for higher mtDNA copy numbers was primarily seen for women with <3 years between blood draw and cancer diagnosis; ORs (95% CIs) for 2(nd), 3(rd), 4(th), and 5(th) quintile of mtDNA copy number were 1.52 (0.61, 3.82), 2.52 (1.03, 6.12), 3.12 (1.31, 7.43), and 3.06 (1.25, 7.47), respectively, compared with the 1(st) quintile (P(trend) = 0.004). There was no association between mtDNA copy number and breast cancer risk among women who donated a blood sample ≥3 years before breast cancer diagnosis (P(trend) = 0.41). This study supports a prospective association between increased mtDNA copy number and breast cancer risk that is dependent on the time interval between blood collection and breast cancer diagnosis. Future studies are warranted to confirm these findings and to elucidate the biological role of mtDNA copy number in breast cancer risk.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota, United States of America. thya0003@umn.edu
authors.forename: Bharat
authors.initials: B
authors.lastname: Thyagarajan
authors.forename: Renwei
authors.initials: R
authors.lastname: Wang
authors.forename: Heather
authors.initials: H
authors.lastname: Nelson
authors.forename: Helene
authors.initials: H
authors.lastname: Barcelo
authors.forename: Woon-Puay
authors.initials: WP
authors.lastname: Koh
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Yuan
mesh_terms: D000704:Analysis of Variance; D044466:Asian People / Q000235:genetics*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D016022:Case-Control Studies; D056915:DNA Copy Number Variations / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D056726:Genetic Association Studies; D006801:Humans; D016015:Logistic Models; D016017:Odds Ratio; D060888:Real-Time Polymerase Chain Reaction; D012307:Risk Factors; D012846:Singapore / Q000453:epidemiology
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial