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Previous studies have shown that expression of the immune co-stimulator B7.1 reduces the tumorigenicity of some, but not all, malignant cell lines. However, B7.1-expressing tumor cells are not very effective in inducing the rejection of established tumors. This may in part be due to induction of anergy in the potentially reactive T cells. Previous studies have shown that IL-2 can reverse the anergic state both in vitro and in vivo. Therefore, we have examined the effect of retrovirus-mediated delivery and expression of murine B7.1 and interleukin-2 on tumor formation and rejection of established MHC class I+/II- NC adenocarcinomas. Neither the expression of B7.1 nor IL-2 alone had a significant effect on NC tumorigenicity. In contrast, combined expression of B7.1 and IL-2 substantially decreased the tumorigenicity of these cells in the immunecompetent syngeneic hosts. T-cell depletion studies show this to be dependent primarily on the activation of CD4+ cells. Furthermore, distant subcutaneous injection of irradiated NC/IL-2/B7.1 can induce, much more effectively than NC/B7.1 or NC/IL-2, the rejection of small NC tumors, and prevent the recurrence of large surgically resected tumors. Together, these results suggest that tumor cells genetically modified to express B7.1 and IL-2 can induce the immune-mediated rejection of established class II- tumors by a mechanism involving CD4+ cells.

Original publication




Journal article


Hum gene ther

Publication Date





477 - 488


Adenocarcinoma, Animals, Antigens, Neoplasm, B7-1 Antigen, CD4-Positive T-Lymphocytes, CD8-Positive T-Lymphocytes, Enzyme-Linked Immunosorbent Assay, Female, Flow Cytometry, Genetic Therapy, Genetic Vectors, Humans, Infant, Interleukin-2, Mammary Neoplasms, Experimental, Mice, Mice, Inbred Strains, Mice, SCID, Neoplasm Recurrence, Local, Transfection, Tumor Cells, Cultured