title: Localized expression of GITR-L in the tumor microenvironment promotes CD8+ T cell dependent anti-tumor immunity.
abstract: The systemic administration of an agonist antibody against glucocorticoid-induced tumor necrosis factor receptor related (GITR) protein has been shown to be effective in overcoming immune tolerance and promoting tumor rejection in a variety of murine tumor models. However, little is known regarding the functional consequence of ligation of GITR with its natural ligand (GITR-L) in the context of regulatory T cell (Treg) suppression in vivo. To determine the mechanism of GITR-L action in vivo, we generated a panel of tumor cell clones that express varying levels of GITR-L. The ectopic expression of GITR-L on the tumor cell surface was sufficient to enhance anti-tumor immunity and delay tumor growth in syngeneic BALB/c mice. Within the range examined, the extent of anti-tumor activity in vivo did not correlate with the level of GITR-L expression, as all clones tested exhibited a similar delay in tumor growth. The localized expression of GITR-L on tumor cells led to a significant increase in CD8+ T cell infiltration compared to the levels seen in control tumors. The increased proportion of CD8+ T cells was only observed locally at the tumor site and was not seen in the tumor draining lymph node. Depletion studies showed that CD8+ T cells, but not CD4+ T cells, were required for GITR-L mediated protection against tumor growth. These studies demonstrate that signaling between GITR-L and GITR in the tumor microenvironment promotes the infiltration of CD8+ T cells, which are essential for controlling tumor growth.
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, BSRB 247, 615 Charles E. Young Dr. South, Los Angeles, CA 90095-1570, USA. johncho@ucla.edu
authors.forename: John S
authors.initials: JS
authors.lastname: Cho
authors.forename: Jeffrey V
authors.initials: JV
authors.lastname: Hsu
authors.forename: Sherie L
authors.initials: SL
authors.lastname: Morrison
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000276:immunology*; D005260:Female; D005822:Genetic Vectors; D053450:Glucocorticoid-Induced TNFR-Related Protein; D007108:Immune Tolerance; D051379:Mice; D008807:Mice, Inbred BALB C; D017475:Receptors, Nerve Growth Factor / Q000276:immunology / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000276:immunology / Q000378:metabolism*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism; D014162:Transfection; D048069:Tumor Necrosis Factors / Q000276:immunology / Q000378:metabolism*
chemical_list: D053450:Glucocorticoid-Induced TNFR-Related Protein; D017475:Receptors, Nerve Growth Factor; D018124:Receptors, Tumor Necrosis Factor; C106544:Tnfrsf18 protein, mouse; C478966:Tnfsf18 protein, mouse; D048069:Tumor Necrosis Factors