Irradiated NC Adenocarcinoma Cells Transduced with Both B7.1 and Interleukin-2 Induce CD4⁺-Mediated Rejection of Established Tumors

Abstract

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.

Fusagene vectors: a novel strategy for the expression of multiple genes from a single cistron

“…A large number of studies have shown that the expression of different combinations of therapeutic genes induces a much more efficient antitumour response than expression of single genes in tumour cells. [1][2][3][4][5][6][7][8][9][10][11] However, the relative inefficiency of gene transfer procedures precludes the use of multiple vectors for the transfer and expression of different gene products. In principle, expression of several genes in a single vector can be achieved by inclusion in the vector of multiple expression cassettes each with its own independent promoter.…”

Local versus systemic interleukin-2: Tumor formation by wild-type and B7-1-positive murine melanoma cells

“…A number of tumor models have shown that the combination of B7-1 with IL-2 is more effective than either one alone in preventing outgrowth of inoculated tumor cells. 7,8 The reasons for this are still unclear, which is perhaps not surprising given the plethora of possible effects of IL-2, including natural killer cell proliferation, 18 prevention and reversal of T-cell anergy, 19,20 and mimicry of delayed-type hypersensitivity.…”

“…8,12 Cells were cultured in Dulbecco's modified Eagle's medium containing 10% heat-inactivated fetal calf sera, 2 mM L-glutamine, 200 U/mL penicillin, and 200 g/mL streptomycin (all from Sigma).…”

“…6 Although B7-1 or IL-2 alone in some animal models each have little effect, the dual transduction of tumor cells to produce both B7-1 and IL-2 can be highly effective in preventing tumor formation. 7,8 Using the K1735 tumor model, we have investigated whether the coexpression of B7-1 and IL-2 is more efficient in preventing tumor formation than either one alone. In addition, if IL-2 can be administered systemically in combination with tumor cells expressing B7-1, then the IL-2 dosage required may be reduced and the side effects may be minimized.…”

“…In other models, IL-2 secretion must be combined with other immunomodulators to be fully effective. 8,22 Systemic administration of IL-2 may more rigorously require additional cytokine/costimulation, having little or no effect by itself 24,25 and being more effective in combination with tumor cells secreting other cytokines. 9 Our results indicate that i.p.…”