How many copies of mitochondrial DNA a tumor carries tracks with its mutations — and its response to chemotherapy
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Every cell carries many copies of mitochondrial DNA, and the number — mtDNA copy number — varies widely between tissues and tumors. A study in The FEBS Journal (2026) asked what that number means across cancers, and found it is anything but background noise.
Reporting summarized October 7, 2026 by MedicalXpress describes a multi-cancer analysis led by Riddhiman Dhar at the Indian Institute of Technology Kharagpur: higher mtDNA copy number tracked with greater mutational load, with expression of genes supporting tumor growth and survival, and with a compensatory signature suggesting cells boosting copy number to offset impaired mitochondrial function.
Why would a tumor raise its mitochondrial DNA count?
One reading is compensation: if each mitochondrion works less well, carrying more mitochondrial genomes is a way to hold energy production up. The same analysis linked copy-number variation to differential expression of chemotherapy-response genes — which is why the authors argue mtDNA copy number could help shape future cancer-management strategies, as a biomarker to study rather than a test ready for clinic use.
What is the careful takeaway?
Correlation is the key word. Copy number associates with progression and therapy-response signatures; this study does not show that changing copy number changes a tumor's course, and no validated clinical test follows from it yet. It does reinforce a theme running through this week's coverage: in cancer, mitochondria are not passive bystanders — their genomes, membranes, and respiratory chains are part of the disease machinery.
Where the evidence stands
- Established: mtDNA copy number varies across cancers and can reflect mitochondrial function and cellular compensation.
- Preliminary: A multi-cancer FEBS Journal analysis (2026) associated mtDNA copy number with mutational load, tumor growth and survival gene expression, and chemotherapy-response gene signatures.
- Absent: A validated clinical test or treatment strategy based on mtDNA copy number, and evidence that altering copy number alters cancer outcomes.
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