Mitochondrial DNA copy number and cancer risks: A comprehensive Mendelian randomization analysis

Area of Science:

• Genetics
• Oncology
• Epidemiology

Background:

• Mitochondrial DNA (mtDNA) is implicated in cancer development, but its copy number (mtDNA-CN) association with cancer risk remains debated.
• Understanding the causal relationship between mtDNA-CN and various cancers is crucial for risk assessment and potential therapeutic strategies.

Approach:

• Utilized Mendelian randomization (MR) analysis with three independent instrumental variable sets from UK Biobank and CHARGE consortium.
• Employed MR-Egger, weighted median, IVW, and weighted mode methods to assess causal associations with 20 cancer types.
• Validated findings using leave-one-out sensitivity analysis and conducted a meta-analysis for pooled results from outcome data in the FinnGen cohort.

Key Points:

• Genetically predicted mtDNA-CN showed no significant association with overall cancer risk (OR = 1.02, 95% CI: 0.95-1.10).
• Subgroup analyses revealed no causal link between mtDNA-CN and breast, lung, prostate, colorectal, and many other cancers.
• A potential association was observed for lip, oral cavity, and testis cancers, but requires cautious interpretation due to small sample sizes.

Conclusions:

• Mitochondrial DNA copy number (mtDNA-CN) does not appear to be a causal factor for the majority of cancer types.
• The study concludes that mtDNA-CN is unlikely to serve as a robust biomarker for predicting overall cancer risk.
• Further research may be needed for specific cancers like lip, oral cavity, and testis, with larger patient cohorts.