title: Tumor-induced regulation of suppressor macrophage nitric oxide and TNF-alpha production. Role of tumor-derived IL-10, TGF-beta, and prostaglandin E2.
abstract: In vitro-activated macrophages (Mphi) co-express cytotoxicity for tumor cells and suppression of lymphocyte proliferation. These Mphi functions increase during tumor growth and are mediated by soluble molecules. Because Mphi-derived nitric oxide (NO) and TNF-alpha mediate both cytotoxicity and suppression, we determined whether fibrosarcoma (Meth-KDE) growth increased Mphi-mediated suppression of T cell proliferation by increasing Mphi NO and TNF-alpha production. Tumor-bearing host peritoneal Mphi produced more NO and TNF-alpha than normal host Mphi when activated with IFN-gamma or LPS, respectively. This tumor-induced increase in Mphi NO and TNF-alpha production mediated suppression of alloantigen-driven T cell proliferation, because treatment with either NG-monomethyl-L-arginine or anti-TNF-alpha Ab blocked tumor-bearing host Mphi-mediated suppression. TNF-alpha did not directly suppress T cells, but it induced Mphi NO production that down-regulated proliferation. When non-tumor-infiltrating peritoneal Mphi were cultured with Meth-KDE cell supernatants, Mphi production of NO and TNF-alpha was strongly down-regulated. The tumor-derived molecules responsible for this inhibition were IL-10, TGF-beta 1, and prostaglandin E2. The experimental evidence leading to this conclusion included: 1) The Meth-KDE cells produced significant levels of these cytokines. 2) Recombinant forms of these cytokines suppressed NO and TNF-alpha production. 3) Ab-mediated absorption of these cytokines from tumor cell supernatants restored NO and TNF-alpha production. 4) Anti-IL-10 and anti-TGF-beta 1 Ab addition to IFN-gamma-stimulated Mphi restored NO production. Culture supernatants of two human carcinoma cell lines and another murine fibrosarcoma suppressed Mphi NO and TNF-alpha production, which was partly mediated by TGF-beta 1 and prostaglandin E2. Collectively, these results suggest that tumor growth promotes distal Mphi suppressor activity by increasing Mphi production of cytotoxic molecules and concomitantly down-regulating the local production of these antitumor molecules.
authors.affiliation: Department of Biology, Microbiology, Virginia Polytechnic Institute and State University, Blacksburg 24061-0406.
authors.forename: D G
authors.initials: DG
authors.lastname: Alleva
authors.forename: C J
authors.initials: CJ
authors.lastname: Burger
authors.forename: K D
authors.initials: KD
authors.lastname: Elgert
mesh_terms: D000818:Animals; D003602:Cytotoxicity, Immunologic; D015232:Dinoprostone / Q000502:physiology*; D007111:Immunity, Cellular; D007166:Immunosuppressive Agents; D016753:Interleukin-10 / Q000502:physiology*; D008213:Lymphocyte Activation; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D009569:Nitric Oxide / Q000378:metabolism*; D012513:Sarcoma, Experimental / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D007166:Immunosuppressive Agents; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D009569:Nitric Oxide; D015232:Dinoprostone