AB99. Association of mitochondrial DNA copy number in peripheral blood leukocytes with risk and prognosis of prostate

OBJECTIVE: To investigate the relationship between mitochondrial DNA (mtDNA) copy number in peripheral blood leukocytes (PBLs) and the risk and the prognosis of prostate cancer (PCa). METHODS: In a case-control study of 196 PCa patients and 196 age-paired normal controls, the association between mtDNA copy number in PBLs and PCa risk was evaluated. The relative mtDNA copy number was measured by using real-time PCR. Among the case cohort, 89 patients were subject to follow-up. Two endpoints i.e., progression-free survival (PFS) and overall survival (OS), were selected to evaluate the association between the prognosis of PCa and the mtDNA copy number. RESULTS: PCa patients had significantly higher mtDNA copy numbers than controls (medians 0.91 and 0.82, respectively; P<0.001). High mtDNA copy number was also associated with an increased risk of PCa (highest quartile vs. lowest: odds ratio =2.52, 95% confidence intervals: 1.35-4.70; Ptrend =0.011). Patients with higher AJCC stage and Gleason score tended to have higher mtDNA copy numbers (P=0.002 and P=0.012, respectively). Cox univariate and multivariate survival analysis indicated that mtDNA copy number was an effective predictor of PFS and OS. The Kaplan-Meier survival curves revealed that high mtDNA copy number was associated with poor PFS and OS in patients with PCa (P=0.007 and P<0.001, respectively). CONCLUSIONS: Our findings provide the first evidence that increased mtDNA copy number in PBLs is significantly associated with an increased risk of PCa and, similarly, a poor prognosis in PCa patients. Quantification of mtDNA copy number in PBLs could be helpful to diagnosis and prognosis of PCa.