Lymphocytes and thyroid cancer: more to it than meets the eye?

Immune responses by innate and adaptive immune cells are crucial for the suppression of carcinogenesis and tumor spread. Effector T cells such as, cytotoxic CD8(+) T (CTL), natural killer (NK), and NK T cells (NKT cells) prevent tumor growth by their ability to induce apoptosis in cancer cells. To circumvent anti-tumor immunity, tumors commonly attract regulatory T cells (Treg), which suppress the function of CTL and NKT cells in a contact- and cytokine-dependent manner. Recent findings in patients with thyroid cancer have suggested that an imbalance between immune suppressive and anti-tumor cells occurs during thyroid carcinogenesis. However, the composition and regulation of immune responses in thyroid cancer are still elusive and a comprehensive immune profile of thyroid cancer is missing. In this issue of Endocrine-Related Cancer, Imam et al. compare immune profiles between patients with papillary thyroid carcinoma and autoimmune thyroiditis. Their data suggest that an imbalance between immunosuppressive Treg cells and effector T cells occurs during papillary thyroid carcinogenesis. Their study identified double-negative T cells as a novel key factor involved in this process. Future research is required to recapitulate these findings, to elucidate the mechanisms by which the immune response is regulated and to evaluate if this process might be used for the therapeutical management of thyroid cancer.