Mitochondrial transfer-driven immune evasion in the tumor microenvironment.

The tumor microenvironment (TME) is a complex landscape where metabolic interactions significantly dictate antitumor immunity. Immune evasion in cancer is typically discussed in terms of inhibitory receptors and ligands, suppressive cytokines, defective antigen presentation, and metabolic competition. However, recent evidence reveals that intercellular mitochondrial transfer adds a new mechanism of immune evasion in the TME. The mitochondrial fitness of T cells is central to sustained effector function, memory formation, and responsiveness to immune-checkpoint blockade. Tumor cells can act as pathogenic mitochondrial donors, transferring functional or dysfunctional mitochondria to neighboring T cells via tunneling nanotubes and extracellular vesicles. This process involves a mitophagy imbalance that leads to the homoplasmic replacement of endogenous mitochondria, thereby driving T-cell senescence, impairing memory formation and long-term antitumor function, and ultimately weakening cancer immunosurveillance. Overall, mitochondrial transfer should be considered a new part of the tumor immune evasion framework. It also provides new therapeutic opportunities for improving cancer immunotherapy.