Gene transfer to liver cancer cells of B7-1 plus interleukin 12 changes immunoeffector mechanisms and suppresses helper T cell type 1 cytokine production induced by interleukin 12 alone.
To investigate the cooperative effect of B7-1 and IL-12 in the induction of antitumor activity, we have developed retroviral vectors encoding human B7-1, murine IL-12, or both B7-1 and IL-12 coordinately. Murine transformed liver cells (BNL) were engineered to stably express B7-1, IL-12, or both by infection with corresponding retroviruses. No tumor was observed in 20, 75, and 95% of mice receiving, respectively, B7-1-, IL-12-, and B7-1/IL-12-modified tumor cells after 250 days of inoculation. In contrast, injection of parental BNL or BNL/Neo cells resulted in lethal tumor progression in all mice. Protection against rechallenge with parental tumor cells was observed only in mice who had rejected BNL/IL-12, but not in animals that rejected BNL/B7-1 or BNL/B7-1-IL-12. Growth of parental tumor cells was significantly delayed by simultaneous injection in a distant site of irradiated tumor cells engineered to express IL-12 or both B7-1 and IL-12 but not B7-1 alone. BNL/B7-1 and BNL/B7-1-IL-12 showed similar efficacy in these experiments. Antitumor immunity induced by B7, with or without IL-12, was found to depend mainly on CD4+ T cells with a minor contribution of a non-T cell mechanism; whereas the effect of IL-12 was dependent on CD8+ T cells and on non-T cell effectors. Immunization of mice with IL-12-modified BNL cells induced secretion of a Thl pattern of cytokines while immunization with cells expressing both IL-12 and B7-1 resulted in inhibition of IFN-gamma production. Immunization with BNL/B7-1-IL-12 cells in the presence of anti-human B7-1 MAb resulted in restoration of IFN-gamma production to the levels found in animals injected with BNL/IL-12 cells. To summarize, in our model coexpression of B7-1 and IL-12 in tumor cells does not result in improved antitumoral activity as compared with expression of IL-12 alone. This may be related to the fact that B7-1 changes the mechanisms of antitumor immunity and inhibits IFN-gamma production induced by IL-12 in vivo.
Sun
Y
Y
Department of Internal Medicine, School of Medicine, University of Navarra, Pamplona, Spain.
Qian
C
C
Peng
D
D
Prieto
J
J
D000818:Animals; D018122:B7-1 Antigen / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D018014:Gene Transfer Techniques; D006801:Humans; D007167:Immunotherapy; D007371:Interferon-gamma / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000494:pharmacology*; D008114:Liver Neoplasms, Experimental / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D018417:Th1 Cells / Q000378:metabolism*
D018122:B7-1 Antigen; D017931:DNA Primers; D018664:Interleukin-12; D007371:Interferon-gamma