IMMUNOBIOLOGY

It has been reported that ectopically ex-pressed interleukin-17 (IL-17) in tumor cells suppresses tumor progression through enhanced antitumor immunity in immune competent mice or promote tu-mor progression through an increase in inflammatory angiogenesis in immune-deficient mice. The role of endogenous IL-17 in tumor immunity remains unde-fined. Here we showed that tumor growth and lung metastasis were enhanced in IL-17–deficient mice, associated with de-creased interferon- natural killer cells and tumor specific interferon- T cells in the tumor draining lymph nodes and tumors. Together with the published data showing that in vitro transforming growth factor- and IL-6–polarized Th17 cells in-duce tumor regression, our work sup-ports the notion that endogenous IL-17 or/and Th17 cells may play a protective role in tumor immunity. (Blood. 2009;114: 357-359