In a new study published in Science titled, “Mitochondrial metabolism and signaling direct dendritic cell function in antitumor immunity,” researchers from St. Jude Children’s Research Hospital have uncovered a new metabolic mechanism for how tumors disable immune “gatekeeper” cells that initiate response in the presence of cancer. The results offer a new path to improve immunotherapy.

Dendritic cells alert and activate tumor-killing immune cells as a critical part of anticancer immune response. The authors found that tumors reduce dendritic cell function by minimizing mitochondrial fitness to prevent anticancer immune response. Correspondingly, boosting mitochondrial function in dendritic cells enhances antitumor immune activity and strengthens the efficacy of existing immunotherapies.  

Within the nutrient-sparse tumor microenvironment, dendritic cells progressively lose mitochondrial activity, which drives cell dysfunction and weakens immune defenses against cancer. When dendritic cells with high mitochondrial activity were introduced into tumors in preclinical mouse models, results showed that immunogenic activity was restored while improving tumor control.  

“We found that tumors reprogram mitochondrial metabolism in dendritic cells, reducing their ability to activate the immune system against cancer,” said Hongbo Chi, PhD, St. Jude Department of Immunology chair and corresponding author of the study. “By enhancing mitochondrial function, we could restore dendritic cell activity and rescue antitumor immunity.”  

Immunotherapies for cancer, such as immune checkpoint blockade, have greatly improved care for many malignancies, but have not been successful in all cancers. To determine whether these findings could improve immunotherapy effectiveness in tumor-bearing mice, the authors evaluated the administered dendritic cells with high mitochondrial activity in combination with immune checkpoint blockade. 

“We saw the most pronounced therapeutic effect in mice treated with the combination of dendritic cells that had high mitochondrial activity and immune checkpoint blockade,” said co-first author Zhiyuan You, PhD, researcher at St. Jude Department of Immunology. “Those combinations synergistically slowed or stopped tumor growth and extended survival far more than either treatment alone.”  

To test long-term effects, the researchers exposed combination therapy treated mice to a new tumor after a few months. New tumor growth stopped for these mice, indicating durable, long-term immune memory. 

To better understand the relationship between mitochondrial function and dendritic cells, the researchers examined metabolic pathways affected by the tumor microenvironment. They identified a signaling axis composed of two proteins, OPA1 and NRF1, that regulate communication between mitochondria and the nucleus. Expression was greatly downregulated in dendritic cells during tumor progression and acted as a metabolic switch to shut down dendritic cell immunogenic activity.  

“We’re seeing a direct regulation of dendritic cells by the tumor microenvironment,” said co-first author Jiyeon Kim, PhD, researcher at St. Jude Department of Immunology. “We have characterized how that results in mitochondrial reprogramming of dendritic cells to benefit cancer, giving us new opportunities to reverse the process.”  

The study’s mechanistic insights enable new directions to rewire dendritic cell function and enhance cancer treatments.  

“These findings reinforce the central role of dendritic cells in cancer immunity,” Chi said. “By exploring their mitochondrial function in the tumor microenvironment, we have provided a proof-of-principle of how we may be able to improve the next generation of immunotherapies.” 

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