New Inherited Factor in Melanoma Immunotherapy Resistance Discovered: Mitochondrial DNA

Although immunotherapy is a promising option for many patients with metastatic melanoma, not everyone responds in the same way. Predicting response is crucial for choosing the most appropriate treatment plan. A recent study found that maternally inherited genetic differences, namely mitochondrial DNA, may play a critical role in predicting immunotherapy resistance. This striking finding could open a new chapter in personalized cancer treatment.

In cancer treatment, particularly for aggressive diseases such as metastatic melanoma, immune checkpoint inhibitors (ICIs) have brought revolutionary advances. However, while approximately half of these treatments are effective, the other half encounter resistance. Understanding and predicting this resistance is vital to avoid unnecessary treatments and offer more suitable alternatives. A research team led by Kelsey Monson and Robert Ferguson at New York University (NYU) Langone Health identified an important genetic difference that sheds light on this question in a study published in Nature Medicine .

The Mystery of Mitochondrial Haplogroups and Their Effects on Immune Cells

The research focuses on maternally inherited mitochondrial haplogroups . Unlike nuclear DNA, mitochondrial DNA is inherited only from the mother. Mitochondria were already known to play an important role in immune-cell development. This study provides new evidence that deepens our understanding of how mitochondrial genetics affects the immune system.

Groundbreaking Study: Mitochondrial Haplogroup T and Immunotherapy Resistance

The researchers genetically analyzed 1225 patients with metastatic melanoma who had participated in the CheckMate-067 study . Their hypothesis was that inherited differences in mitochondrial DNA could influence the immune response.

Patients carrying mitochondrial haplogroup T were 3.46 times less likelyto respond to immune checkpoint inhibitors than patients in other groups. This haplogroup was found in approximately 12% of patients with melanoma.

NYU Langone Health epidemiologist Dr. Kelsey Monson said: “Our study shows for the first time that mitochondrial haplogroup T may be an inherited biomarker for identifying the risk of nonresponse in patients with metastatic melanoma.”

Although both drug regimens were effective in more than 50% of all patients, the rate among haplogroup T carriers was only 18% . This finding was validated in 675 patients of similar age and sex.

In addition, among haplogroup T carriers who did not respond, CD8+ T cells were found to be insufficiently mature. This reduces the immune system's ability to recognize and destroy cancer.

This was associated with high resistance to reactive oxygen species (ROS) in haplogroup T mitochondria. ROS normally serve as signals that activate T cells.

Because of this resistance, however, immune cells cannot be “fired up” to begin fighting cancer. In other words, mitochondrial haplogroup T may act as a “protective shield” that suppresses immune cells, an unfavorable effect in the fight against cancer.

How Was Mitochondrial Haplogroup T Tested?

DNA was isolated from peripheral blood samples collected before treatment. It was analyzed using whole-genome sequencing (WGS) or ultra-low-coverage sequencing (0.5× WGS) . Variants were identified with GATK software, and Haplogrep 3 was then used to classify haplogroups according to Phylotree v17.1. This allowed mitochondrial characteristics to be identified noninvasively with high accuracy.

Future Implications and the Importance of Personalized Treatment

These findings offer an opportunity to develop a test that identifies likely nonresponders before immunotherapy begins, allowing alternative approaches to be considered earlier.

The study deepens our understanding of the relationship between mitochondrial genetics and immune-response biology. The findings suggest that mitochondrial variants may also matter in cancers other than melanoma. This is a promising step toward personalizing treatment response across broader patient populations.

Conclusions and Next Steps: Toward Personalized Cancer Treatment

This research provides a new framework for understanding immunotherapy resistance in metastatic melanoma. Identifying haplogroup T carriers early could reduce unnecessary treatment burden and guide patients toward more effective options.

The researchers say these findings will open avenues for further investigation to clarify the roles of mitochondrial genetics, ROS metabolism, and antitumor T-cell activity in future cancer treatments. Prospective clinical studies are also planned to determine whether these results apply to other cancer types and haplogroups.