Natural Killer Cell and Extracellular Vesicle-Based Immunotherapy in Thyroid Cancer: Advances, Challenges, and Future Perspectives.

Thyroid cancer, the most frequently occurring endocrine neoplasm, comprises a heterogeneous group of histological subtypes, spanning from the indolent papillary thyroid carcinoma (PTC) to the rapidly progressive and lethal anaplastic thyroid carcinoma (ATC). Although conventional therapies, such as surgery and radioactive iodine (RAI), are effective for differentiated thyroid cancers, treatment resistance and poor prognosis remain major challenges in advanced and undifferentiated forms. In current times, growing attention has been directed toward the potential of Natural Killer (NK) cells as a promising immunotherapeutic avenue. These innate immune cells are capable of direct cytotoxicity against tumor cells, but their efficiency is frequently compromised by the immunosuppressive tumor microenvironment (TME), which inhibits NK cell activation, infiltration, and persistence. This review explores the dynamic interaction between NK cells and the TME in thyroid cancer, detailing key mechanisms of immune evasion, including the impact of suppressive cytokines, altered chemokine landscapes, and inhibitory ligand expression. We further discuss latest advancements in NK cell-based immunotherapies, including strategies for ex vivo expansion, genetic modification, and combinatorial approaches with checkpoint inhibitors or cytokines. Additionally, emerging modalities, such as NK cell-derived extracellular vesicles, are addressed. By combining mechanistic insights with advancing therapeutic techniques, this review provides a comprehensive perspective on NK cell-based interventions and their future potential in improving outcomes for patients with thyroid cancer.