Anti-tumor immunity generated by tumor cells engineered to express B7-1 via retroviral or adenoviral gene transfer

We engineered B7-1 retroviral and adenoviral gene transfer systems and studied them in four immunogenic tumor models. M-MSV tumor cells, but not K-Balb, 38.2 and 205 tumor cells, when expressing B7-1 by retroviral transduction were rejected and conferred protection against a tumor challenge. Transient expression of B7-1 after transduction with adenoviruses was less efficient. We observed enhanced cytotoxic T-lymphocyte activity accompanied by increased secretion of IL-6, IFNγ and GM-CSF. GM-CSF secretion correlated with tumor rejection. Enhanced IFNγ but unchanged IL-4 secretion suggested a T-helper 1-mediated anti-tumor immune response.