The study, led by corresponding author Riddhiman Dhar, PhD, of the Indian Institute of Technology Kharagpur, took a multi-cancer approach, examining the relationship between mtDNA copy number and key features of tumor biology across different cancer types. The central question was deceptively simple: does the quantity of mitochondrial DNA in a cancer cell correlate with the behavior and progression of the disease? The answer, according to the research, appears to be yes. The team found a clear correlation between mtDNA copy number and the extent of genetic mutations within cancer cells, a measure known as mutational load, which is itself closely tied to how aggressive and advanced a cancer can be.

To understand why this finding matters, it helps to appreciate the unusual nature of mitochondrial DNA. Unlike the vast majority of our genetic material, which is packaged into chromosomes inside the cell nucleus, mtDNA resides within the mitochondria themselves. Humans typically inherit mtDNA exclusively from their mothers, and each mitochondrion can contain multiple copies of the mitochondrial genome, with a single cell housing hundreds to thousands of copies in total. This copy number is not fixed. It can rise or fall depending on the energy demands of the cell, environmental stresses, and disease states. In cancer, where cells divide rapidly and metabolism is dramatically rewired, the regulation of mtDNA copy number becomes a potentially critical variable.

One of the most striking observations in the new study concerns compensation. When mitochondrial function is impaired, the researchers found that an increase in mtDNA copy number showed a signature of compensation for that impaired function. In other words, cancer cells appear to respond to malfunctioning mitochondria by producing more copies of the mitochondrial genome, perhaps in an attempt to maintain adequate energy production despite underlying defects. This kind of compensatory mechanism has been observed in mitochondrial diseases before, but seeing it clearly reflected in cancer cells adds a new dimension to our understanding of tumor metabolism. It suggests that mtDNA copy number is not merely a passive byproduct of cellular state but an actively regulated feature that cancer cells may exploit to survive under stress.

The implications extend beyond energy production. The study also found that variation in mtDNA copy number was associated with differential expression of genes linked to chemotherapy response. This is a particularly significant result because chemotherapy remains a mainstay of cancer treatment worldwide, and predicting which patients will respond well to a given drug is one of the great challenges of modern oncology. If the amount of mitochondrial DNA in tumor cells influences the expression of genes involved in drug response, then mtDNA copy number could eventually serve as a biomarker, helping clinicians tailor treatment decisions to the specific biology of a patient’s tumor.

Furthermore, the research connected mtDNA copy number to various other aspects of cancer biology. Notably, high mtDNA copy number was linked with the expression of genes that support tumor growth and survival. This finding hints at a possible mechanism by which abundant mitochondrial DNA could actively promote cancer progression: by bolstering the cellular machinery that tumors need to proliferate and evade cell death. Cancer cells are known for their metabolic flexibility, often shifting their energy production away from normal oxidative phosphorylation toward glycolysis even in the presence of oxygen, a phenomenon called the Warburg effect. Yet mitochondria remain indispensable even in highly glycolytic tumors, contributing to biosynthesis, signaling, and cell survival pathways. The new results suggest that the mitochondrial genome’s abundance may be woven into these processes more intimately than scientists had realized.

The correlation between mtDNA copy number and mutational load is especially intriguing from an evolutionary perspective. Tumors evolve over time, accumulating mutations in their nuclear DNA that drive uncontrolled growth, immune evasion, and metastasis. A higher mutational load generally reflects a more evolved, and often more aggressive, malignancy. The finding that mtDNA copy number tracks with this mutational burden raises the possibility that mitochondrial genetic status and nuclear genome instability are interconnected processes in cancer evolution. Whether changes in mtDNA copy number contribute directly to genomic instability, or whether both are shaped by a common underlying stress, remains an open question that the researchers say warrants deeper investigation.

Speaking about the significance of the work, Dhar emphasized its potential to reshape how scientists think about mitochondria in cancer. The results, he noted, reveal a close association of mtDNA copy number with cancer progression and therapy response, and could pave the way for deeper investigations into the role of mitochondria in cancer that will enable new cancer management strategies. Such strategies could range from improved prognostic assessments, in which mtDNA copy number helps gauge how advanced or aggressive a tumor is likely to be, to therapeutic interventions that target mitochondrial function or the pathways that regulate mitochondrial genome maintenance.

It is worth stressing that the study establishes correlations rather than definitive proof of causation. A correlation between mtDNA copy number and cancer severity does not by itself demonstrate that altering mtDNA copy number will change the course of the disease. Future experimental work, including studies in cell and animal models, will be needed to determine whether manipulating mitochondrial DNA abundance can directly influence tumor behavior or treatment sensitivity. Nevertheless, the breadth of the associations uncovered in this multi-cancer analysis makes a compelling case that mtDNA copy number deserves attention as a key determinant of cancer biology, one that has often been overshadowed by the focus on nuclear mutations.

The research, published under the title Multi-cancer analysis reveals mtDNA copy number as a key determinant of mutational load and cancer progression, arrives at a moment when mitochondrial biology is enjoying renewed attention across medicine. Mitochondrial dysfunction has been implicated in neurodegenerative diseases, aging, metabolic disorders, and now increasingly in cancer. As sequencing technologies and computational analyses grow more powerful, researchers are able to probe the mitochondrial genome and its copy number with unprecedented precision across large collections of tumor samples. Studies like this one, which integrate mitochondrial genetics with mutation data and gene expression profiles across multiple cancer types, exemplify a growing trend toward viewing the cancer cell as an integrated system in which nuclear and mitochondrial genomes interact dynamically. If subsequent research confirms and extends these findings, the humble mitochondrial genome, long a footnote in cancer genetics, could move to the center of the stage, offering new biomarkers for prognosis, new predictors of chemotherapy response, and potentially new targets for the management of one of humanity’s most formidable diseases.

Subject of Research: The relationship between mitochondrial DNA copy number and cancer progression and therapy response

Article Title: Does mitochondrial DNA affect cancer progression?

Article References: Does mitochondrial DNA affect cancer progression?. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: mitochondrial DNA, mtDNA copy number, cancer progression, mutational load, tumor metabolism, chemotherapy response, gene expression, mitochondria, The FEBS Journal, cancer biomarkers, tumor growth, compensatory mechanisms