title: IL-12 rapidly alters the functional profile of tumor-associated and tumor-infiltrating macrophages in vitro and in vivo.
abstract: Tumor-associated macrophages (TAMs) play a major role in promoting tumor growth and metastasis and in suppressing the antitumor immune response. Despite the immunosuppressive environment created by the tumor and enforced by tumor-associated macrophages, treatment of tumor-bearing mice with IL-12 induces tumor regression associated with appearance of activated NK cells and activated tumor-specific CTLs. We therefore tested the hypothesis that IL-12 treatment could alter the function of these tumor-associated suppressor macrophages. Analysis of tumor-infiltrating macrophages and distal TAMs revealed that IL-12, both in vivo and in vitro, induced a rapid (<90 min) reduction of tumor supportive macrophage activities (IL-10, MCP-1, migration inhibitory factor, and TGFbeta production) and a concomitant increase in proinflammatory and proimmunogenic activities (TNF-alpha, IL-15, and IL-18 production). Similar shifts in functional phenotype were induced by IL-12 in tumor-infiltrating macrophages isolated from the primary tumor mass and in TAMs isolated from lung containing metastases, spleen, and peritoneal cavity. Therefore, although TAMs display a strongly polarized immunosuppressive functional profile, they retain the ability to change their functional profile to proinflammatory activities given the appropriate stimulus. The ability of IL-12 to initiate this functional conversion may contribute to early amplification of the subsequent destructive antitumor immune response.
authors.affiliation: Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, KY 40292, USA.
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Watkins
authors.forename: Nejat K
authors.initials: NK
authors.lastname: Egilmez
authors.forename: Jill
authors.initials: J
authors.lastname: Suttles
authors.forename: Robert D
authors.initials: RD
authors.lastname: Stout
mesh_terms: D000818:Animals; D018827:Carcinoma, Lewis Lung / Q000276:immunology*; D002465:Cell Movement / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis; D007249:Inflammation / Q000276:immunology; D018664:Interleukin-12 / Q000494:pharmacology* / Q000627:therapeutic use; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009369:Neoplasms / Q000276:immunology
chemical_list: D016207:Cytokines; D018664:Interleukin-12