title: Synergistic activation of macrophages via CD40 and TLR9 results in T cell independent antitumor effects.
abstract: We have previously shown that macrophages (Mphi) can be activated by CD40 ligation to become cytotoxic against tumor cells in vitro. Here we show that treatment of mice with agonistic anti-CD40 mAb (anti-CD40) induced up-regulation of intracellular TLR9 in Mphi and primed them to respond to CpG-containing oligodeoxynucleotides (CpG), resulting in synergistic activation. The synergy between anti-CD40 and CpG was evidenced by increased production of IFN-gamma, IL-12, TNF-alpha, and NO by Mphi, as well as by augmented apoptogenic effects of Mphi against tumor cells in vitro. The activation of cytotoxic Mphi after anti-CD40 plus CpG treatment was dependent on IFN-gamma but not TNF-alpha or NO, and did not require T cells and NK cells. Anti-CD40 and CpG also synergized in vivo in retardation of tumor growth in both immunocompetent and immunodeficient mice. Inactivation of Mphi in SCID/beige mice by silica treatment abrogated the antitumor effect. Taken together, our results show that Mphi can be activated via CD40/TLR9 ligation to kill tumor cells in vitro and inhibit tumor growth in vivo even in immunocompromised tumor-bearing hosts, indicating that this Mphi-based immunotherapeutic strategy may be appropriate for clinical testing.
authors.affiliation: Department of Human Oncology and Comprehensive Cancer Center, University of Wisconsin, Madison, WI 53792, USA. buhtoiarov@humonc.wisc.edu
authors.forename: Ilia N
authors.initials: IN
authors.lastname: Buhtoiarov
authors.forename: Hillary D
authors.initials: HD
authors.lastname: Lum
authors.forename: Gideon
authors.initials: G
authors.lastname: Berke
authors.forename: Paul M
authors.initials: PM
authors.lastname: Sondel
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Rakhmilevich
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology; D019013:CD40 Antigens / Q000276:immunology / Q000378:metabolism*; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D008213:Lymphocyte Activation / Q000276:immunology; D008262:Macrophage Activation / Q000276:immunology*; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D009374:Neoplasms, Experimental / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D051217:Toll-Like Receptor 9 / Q000276:immunology / Q000378:metabolism*
chemical_list: D019013:CD40 Antigens; D016207:Cytokines; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9