Abstract 4486: Mitochondrial DNA copy number is associated with colorectal cancer risk

Abstract

Abstract Background: Mitochondrial DNA (mtDNA) copy number variation is common in colorectal tumors and one case control study showed mtDNA copy number to be associated with increased colorectal cancer risk. Data on mtDNA copy number and colorectal cancer risk in prospective cohorts is lacking. Objectives: We evaluated the association between mtDNA copy number in peripheral blood and colorectal cancer risk among participants of the Singapore Chinese Health Study. Methods: We conducted a nested case-cohort study of 422 colorectal cancer cases (168 incident cases with pre-diagnostic blood and 254 prevalent cases with post-diagnostic blood) and 880 controls who were free of colorectal cancer at blood draw. The relative mtDNA copy number was measured using real time PCR. Analysis of covariance and logistic regression methods were employed to examine the association between mtDNA copy number and colorectal cancer risk. Results: mtDNA copy number was significantly higher among colorectal cancer cases than controls (geometric mean: 0.62 vs. 0.50, p<0.0001). There was a U shaped relationship between the mtDNA copy number and colorectal cancer risk. Individuals in the low and high mtDNA copy numbers were at increased risk of colorectal cancer; odds ratios (95% confidence interval) for developing colorectal cancer for the lowest and highest quartile of mtDNA copy numbers were 1.83 (1.16-2.90) and 3.54 (2.25-5.55), respectively, compared to those in the second quartile of mtDNA after adjustment for potential confounders (p for curvilinear trend <0.001). The lowest mtDNA copy number quartile was associated with colorectal cancer only in the pre-diagnostic blood samples (OR=3.22, 95% CI:1.51-6.85) but not in the post-diagnostic blood samples (OR=1.36, 95% CI:0.80-2.32), implying that cancer status impacts the mtDNA copy number-colorectal cancer risk association. Conclusions: This is the first study to show a prospective association between mtDNA copy number and colorectal cancer risk. Further studies are needed to confirm this association and understand the biological significance of these observations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4486. doi:1538-7445.AM2012-4486