Optimization of intracerebral tumour protection by active-specific immunization against murine melanoma B16/G3.12.
Development of brain metastases despite extracerebral response to systemic immunotherapy is a common problem in melanoma patients. We have previously described a murine melanoma vaccine of interferon-gamma (IFNgamma)-treated, irradiated syngeneic B16/G3.12 and allogeneic (Cloudman) melanoma cells, plus the adjuvant DETOX, that is protective against subcutaneous (93%) or intracerebral (69%) syngeneic challenge. This study aimed to optimize this vaccine. Groups of nine or 10 mice were immunized five times in 5 weeks with: (i) complete vaccine +/- IFNgamma (VAC+, VAC-); (ii) syngeneic 2 x 106 G3.12 cells plus DETOX (Syn+D), (iii) 2 x 106 allogeneic Cloudman cells plus DETOX (Allo+D); (iv) VAC+ without DETOX (no DETOX); (v) DETOX alone (DETOX); or (vi) phosphate buffered saline (PBS). Mice were challenged subcutaneously with 104 viable G3.12 (or Cloudman cells) and after 35 days intracerebrally with 104 G3.12 cells. Expression of H-2 antigens (measured using fluorescence-activated cell sorting), splenocyte cytotoxicity (measured using 51Cr release) and median overall survival (OAS) were analysed using the log-rank test. VAC+, VAC- and G3.12 mice were equally protected from subcutaneous (s.c.) and intracerebral (i.c.) melanoma challenge (OAS 65 days for s.c., 30 days for i.c.). Protection was less (P < 0.05) in DETOX mice (48 days for s.c.), PBS mice (47 days for s.c., 21 days for i.c.) or no DETOX mice (51 days for s.c.). Allo+D mice showed s.c. (59 days) but not i.c. protection (20 days). IFNgamma incubation did not increase the effect in either the challenge cells or the vaccine cells (P > 0.05). Specific cytotoxicity was seen with G3.12 targets in VAC+ (27%) but not PBS (2%; P < 0.05) mice with equal NK (YAC-1) lysis (10% versus 7%; P< 0.05). Optimal protection against s.c./i.c. experimental murine melanoma was yielded by irradiated syngeneic cells plus DETOX. DETOX alone was not active. Upregulation of H-2 antigens with IFNgamma under these conditions does not augment protection.
Staib
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Department of Medicine and the Kenneth Norris Jr Comprehensive Cancer Center, University of Southern California School of Medicine, Los Angeles, California 90033, USA. ludger.staib@medizin.uni-ulm.de
Harel
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Mitchell
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D000818:Animals; D001344:Autopsy; D001932:Brain Neoplasms / Q000276:immunology / Q000517:prevention & control* / Q000556:secondary*; D019496:Cancer Vaccines / Q000276:immunology* / Q000627:therapeutic use*; D003598:Cytoskeletal Proteins / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D004195:Disease Models, Animal; D015536:Down-Regulation; D004338:Drug Combinations; D005260:Female; D006183:H-2 Antigens / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology; D008050:Lipid A / Q000031:analogs & derivatives* / Q000276:immunology; D008546:Melanoma, Experimental / Q000276:immunology* / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D012878:Skin Neoplasms / Q000276:immunology / Q000473:pathology; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D015996:Survival Rate; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D019496:Cancer Vaccines; D003598:Cytoskeletal Proteins; D004338:Drug Combinations; D006183:H-2 Antigens; D008050:Lipid A; C112124:detox adjuvant; D007371:Interferon-gamma