Interleukin 23 (IL-23) is an inflammatory cytokine which plays a vital role in autoimmune diseases as well as in tumorigenesis. However, the role of IL-23 in tumor procession is still controversial and the underlying mechanism remains unclear. Here we established a stable cell line overexpressing IL-23 to prove that IL-23 promoted tumor growth and pulmonary metastasis through induction of tumor-related inflammation and absence of immune surveillance. IL-23 promotes tumor-associate inflammatory response such as infiltration of M2 macrophages, neutrophils and their elevated secretions of immunosuppressive cytolcines transforming growth factor-beta (TGF-beta), IL-10 and vascular endothelial growth factor (VEGF) into tumor tissues, meanwhile the increase of the matrix metalloprotease MMP9. In addition, IL-23 increases the expression of the endothelial marker CD31 and proliferative marker Ki67 in tumors. Moreover, IL23 induces immunosuppression though reducing the infiltration of CD4(+) and CD8(+)T cells into tumor tissues. In conclusion, IL-23 is a considerable molecular in tumor progression, which simultaneously facilitates processes of pro-tumor inflammation, such as angiogenesis, immunosuppressive cytolcines as well as infiltrations of M2 macrophages and neutrophils, and suppresses antitumor immune responses through reduction of CD4(+) T cells and CD8(+) T cells. (C) 2016 Elsevier Inc. All rights reserved.