St. Jude Scientists Uncover Mechanism of Tumor-Induced Immune Suppression, Paving Way for Enhanced Immunotherapies
Scientists at St. Jude Children's Research Hospital have identified a mechanism by which tumors suppress dendritic cells, which are important for activating the immune system against cancer. The research also demonstrated that restoring the mitochondrial energy production of these cells improved immunotherapy outcomes in preclinical mouse models. The findings detail how tumors reprogram mitochondrial metabolism in dendritic cells, reducing their capacity to mount an anticancer immune response, and suggest avenues for enhancing cancer treatments. The study was published in Science.
Tumors reprogram mitochondrial metabolism in dendritic cells, reducing their capacity to mount an anticancer immune response.
Understanding Tumor-Induced Immune Suppression
Dendritic cells function as "gatekeeper" cells within the immune system, responsible for activating cytotoxic immune cells that target and destroy cancer. Researchers discovered that tumors compromise dendritic cell function by reducing their mitochondrial fitness. This reduction prevents the formation of an effective anticancer immune response.
Within the tumor microenvironment, dendritic cells progressively lose their energy-producing mitochondrial activity. This loss contributes to dendritic cell dysfunction and weakens the body's immune defenses against cancer.
Enhancing Immunotherapy Through Mitochondrial Function
To investigate methods for counteracting this suppression, researchers introduced dendritic cells with elevated mitochondrial activity into tumors in preclinical mouse models. This intervention restored immunogenic activity and improved tumor control.
The study compared the therapeutic effects of administering dendritic cells with high mitochondrial activity, immune checkpoint blockade, or a combination of both in tumor-bearing mice.
The most pronounced therapeutic effect was observed in mice treated with the combination therapy.
This synergistic approach slowed or halted tumor growth and extended survival to a greater extent than either treatment alone. A long-term assessment indicated the establishment of durable immune memory, preventing new tumor growth in treated mice several months later.
Mechanistic Insights into Dendritic Cell Reprogramming
Further investigation into the metabolic pathways influenced by the tumor microenvironment led to the identification of a signaling axis involving two proteins: OPA1 and NRF1. These proteins regulate communication between mitochondria and the cell nucleus.
During tumor progression, the expression of OPA1 and NRF1 was significantly downregulated in dendritic cells. This downregulation acts as a metabolic switch, signaling an energy crisis to the cell. In response, dendritic cells suspend nonessential functions, including their immunogenic activity.
Implications for Cancer Treatment
These mechanistic insights provide a foundation for developing new strategies to modify dendritic cell function. The aim is to enhance cancer treatments and potentially improve future generations of immunotherapies by exploring the mitochondrial function of dendritic cells within the tumor microenvironment.