Tumoral expression of IL-33 promotes Anti-tumor Immune Responses (TUM2P.912)

One major approach of cancer immune therapy is to convert the tumor immunosuppressive microenvironment to one that favors antitumor immune responses. We have recently demonstrated that Interleukin 33 (IL-33) promotes effector functions of CD8 T cells, suggesting a potential function in antitumor immunity. Here we showed that overexpression of IL-33 in two tumor cell lines, 4T1 and B16, potently inhibited tumor growth in vivo. CD45+, CD8+ T cells, NK cells, IFN-γ+ CD8+ T cells and IFN-γ+ NK cells were greatly increased in the IL-33-expressing tumors when compared with those in the control tumors. We further demonstrated that the antitumor effect of IL-33 was dependent on NK cells and CD8 T cells. In contrast, MDSC were greatly decreased in the IL-33-expressing tumors when compared to those in the control tumors. Our results indicate that the intratumoral delivery of IL-33 can be a new strategy of tumor immunotherapy by promoting an immunogenic microenvironment.