TNF is a potent promoter of carcinogenesis and potentially important target for cancer prevention. TNF is produced as functionally distinct transmembrane and soluble molecules (tmTNF and sTNF, respectively), but their individual roles in carcinogenesis are unexplored. We investigated the participation of tmTNF and sTNF in chemically induced carcinogenesis in mice. We found that injection of XPro1595, a dominant-negative TNF biologic (DN-TNF) and specific antagonist of sTNF, decreased tumor incidence and growth, and prolonged survival of 3-methylcholanthrene (MCA)-injected mice. Similar results were obtained following the exclusion of both TNF forms by either TNF-receptor 2-Fc fusion protein (TNFR2-Fc) treatment or TNF gene deletion. In addition, gene deletion of TNFR1, which is preferentially triggered by sTNF, was temporarily blocked, whereas gene deletion of TNFR2, which is preferentially triggered by tmTNF, enhanced MCA-induced carcinogenesis. Concomitantly with carcinogenesis induction, MCA increased circulating IL1α, accumulation of myeloid-derived suppressor cells (MDSC), STAT3 phosphorylation, and immunosuppression in the spleen. In sharp contrast, DN-TNF treatment dramatically decreased IL1α and increased the essential immunoregulatory cytokines IL1β, IL12p70, and IL17 in the peripheral blood of MCA-injected mice. In addition, MDSC accumulation, STAT3 phosphorylation, and immunosuppression in MCA-injected mice were prevented by DN-TNF treatment, TNFR2-Fc treatment, and/or gene deletion of TNF or TNFR1, but not deletion of TNFR2. These findings reveal that sTNF is both an essential promoter of carcinogenesis and a pivotal regulator of MDSCs, and indicate that sTNF could be a significant target for cancer prevention and therapy. Cancer Immunol Res; 4(5); 441-51. ©2016 AACR.
©2016 American Association for Cancer Research.