title: GM-CSF and B7-1 (CD80) co-stimulatory signals co-operate in the induction of effective anti-tumor immunity in syngeneic mice.
abstract: B7-1 (CD80) co-stimulatory molecule gene-transduced Lewis lung carcinoma (LLC) cells (LLC/B7 cells) resulted in remarkable loss of tumorigenicity in syngeneic C57BL/6 mice (87.5% rejection) compared to B7-negative, wild-type LLC (LLC/wt) cells (0% rejection). However, mice that had rejected LLC/B7 cells developed almost no systemic immunity protective against challenge with wild-type tumor cells after 4 weeks (11.8% rejection). Enhancement of MHC class I (H-2Kb) expression of LLC/B7 cells with in vitro interferon-gamma treatment did not result in enhancement of protective immunity. In vivo depletion assay revealed that abrogation of tumorigenicity in LLC/B7 depended on CD8+ T cells but not on CD4+ T cells. However, vaccination of C57BL/6 mice with irradiated LLC cells transduced with GM-CSF (LLC/GM) led to the induction of potent, specific immunity against challenge with the LLC/wt cells after 2 weeks (80.8% rejection). Next, we established a double transfectant of LLC cells expressing both B7-1 and GM-CSF (LLC/GM + B7). The tumorigenicity of these clonal cells was also remarkably suppressed (90% rejection) to the same degree as LLC/B7, whereas that of LLC/GM was not suppressed (0% rejection). Interestingly, mice that had rejected LLC/GM+B7 cells developed enhanced protective immunity against challenge with LLC/wt cells after 4 weeks (55.6% rejection) compared to the results of LLC/B7 cells (11.8%). To evaluate whether co-expression of GM-CSF and B7-1 enabled the tumor cells to activate cytotoxic T cells more efficiently than B7-1 alone, we performed an in vitro killing assay. We found that immunization with LLC/GM+B7 cells resulted in a 3-fold stronger cytotoxic response than that with LLC/B7. Our data indicate that co-transfection of the B7-1 co-stimulatory molecule and GM-CSF genes may be more effective for the induction of stronger protective immunity in this experimental system.
authors.affiliation: Department of Hematology/Oncology, Institute of Medical Science, University of Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sumimoto
authors.forename: K
authors.initials: K
authors.lastname: Tani
authors.forename: Y
authors.initials: Y
authors.lastname: Nakazaki
authors.forename: T
authors.initials: T
authors.lastname: Tanabe
authors.forename: H
authors.initials: H
authors.lastname: Hibino
authors.forename: H
authors.initials: H
authors.lastname: Hamada
authors.forename: M
authors.initials: M
authors.lastname: Azuma
authors.forename: S
authors.initials: S
authors.lastname: Asano
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism*; D018122:B7-1 Antigen / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D019496:Cancer Vaccines / Q000276:immunology / Q000528:radiation effects; D018827:Carcinoma, Lewis Lung / Q000276:immunology* / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D006084:Graft Rejection / Q000276:immunology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation / Q000276:immunology; D014162:Transfection
chemical_list: D000951:Antigens, Neoplasm; D018122:B7-1 Antigen; D019496:Cancer Vaccines; D018076:DNA, Complementary; D015395:Histocompatibility Antigens Class I; D016178:Granulocyte-Macrophage Colony-Stimulating Factor