Fatal attraction: tumor recruitment of myeloid-derived suppressor cells is mediated by IL-17-producing CD8⁺ T cells

The interaction between tumor tissue and the host immune system is critical to tumor development. These interactions are regulated through a variety of immune cells and cytokines. IL-17 is a proinflammatory cytokine produced by Th17 and Tc17 cells that affects the development of cancer. However, the role of IL-17 in influencing tumor growth or in enhancing anti-tumor immunity is somewhat controversial. Zhuang et al. (Gastroenterology 2012, 143:951) elucidated that the IL-17 produced by Tc17 cells plays an important role in the pathogenesis of gastric cancer. Based on the findings of Zhuang et al. and other studies in the literature, we propose a model involving complex interactions between Tc17 cells, regulatory T cells, monocytes, tumor cells, myeloid-derived suppressor cells, and cytotoxic T lymphocytes within the tumor microenvironment.