Mitochondrial transfer in the tumor microenvironment: mechanisms, immunometabolic consequences, and therapeutic implications.

Mitochondrial transfer has emerged as a previously underappreciated layer of intercellular communication within the tumor microenvironment. Accumulating evidence demonstrates its contribution to the metabolic and functional plasticity of both tumor and immune cells. Rather than representing a rare stochastic event, mitochondrial exchange occurs across multiple cell types-including cancer cells, stromal cells, and infiltrating immune cells-via distinct structures such as tunneling nanotubes (TNTs), extracellular vesicles (EVs), gap junctions, and transient cell fusion events. In tumor cells, acquisition of exogenous mitochondria is commonly associated with enhanced oxidative phosphorylation (OXPHOS), improved metabolic adaptation, and increased tolerance to therapeutic stress. Conversely, immune cells that undergo mitochondrial depletion or receive dysfunctional mitochondria frequently display impaired bioenergetic capacity and diminished effector function, thereby contributing to immune dysfunction in the TME. Recent advances in intravital imaging, single-cell technologies, and lineage tracing have provided compelling evidence that mitochondrial transfer is a dynamic, context-dependent and often directional process. Beyond metabolic effects, mitochondrial components, particularly mitochondrial DNA (mtDNA), can engage innate immune pathways including TLR9, NLRP3, and cGAS-STING, thus modulating inflammatory signaling and antitumor immunity. Overall, mitochondrial transfer functions as a bidirectional regulator of immunometabolic states in cancer, with potential either to support tumor progression or to modulate immune responses, depending on cellular context. Understanding the molecular determinants governing this process may offer opportunities to selectively target pathological mitochondrial exchange or to exploit it for therapeutic benefit in cancer immunotherapy. This comprehensive review examines the molecular mechanisms, immunological consequences, and therapeutic implications of mitochondrial transfer in cancer.