Inhibition of transforming growth factor-β-mediated immunosuppression in tumor-draining lymph nodes augments antitumor responses by various immunologic cell types

Abstract

Tumor-draining lymph nodes (DLN) are the most important priming sites for generation of antitumor immune responses. They are also the location where an immunosuppressive cytokine, transforming growth factor-β (TGF-β), plays a critical role in suppressing these antitumor immune responses. We focused on TGF-β-mediated immunosuppression in DLNs and examined whether local inhibition of TGF-β augmented antitumor immune responses systemically in tumor-bearing mice models. For inhibition of TGF-β-mediated immunosuppression in DLNs, C57BL/6 mice subcutaneously bearing E.G7 tumors were administered plasmid DNA encoding the extracellular domain of TGF-β type II receptor fused to the human IgG heavy chain (TGFR DNA) i.m. near the established tumor. In DLNs, inhibition of TGF-β suppressed the proliferation of regulatory T cells and increased the number of tumor antigen-specific CD4+ or CD8+ cells producing IFN-γ. Enhancement of antitumor immune responses in DLNs were associated with augmented tumor antigen-specific cytotoxic and natural killer activity in spleen as well as elevated levels of tumor-specific antibody in sera. The growth of the established metastatic as well as primary tumors was effectively suppressed via augmented antitumor immune responses. Inhibition of TGF-β-mediated immunosuppression in DLNs is significantly associated with augmented antitumor responses by various immunocompetent cell types. This animal model pro-vides a novel rationale for molecular cancer therapeutics targeting TGF-β. ©2009 American Association for Cancer Research.