The IL-17/IL-23 axis of inflammation in cancer: friend or foe?

IL-17, a proinflammatory cytokine that is regulated by IL-23, is crucial for the development of a novel CD4+ T-cell subset called T-helper 17 (Th17) cells, which promotes tissue inflammation in host defense responses against infection, as well as in chronic autoimmune diseases. IL-17 and IL-23 expression, as well as the presence of Th17 cells, have been documented in several human carcinomas, but their function in tumors remains controversial. This review summarizes the current literature on IL-17, IL-23 and Th17 cells in human tumors and animal models of cancer, discussing their possible roles in cancer development and cancer immunity, and presenting a personal perspective of this research area.