Targeting gamma interferon to tumor cells by a genetically engineered fusion protein secreted from myeloma cells

Abstract

The construction, synthesis and expression of a genetically engineered bifunctional antibody/cytokine fusion protein is described. To target IFN-τ to tumor cells, recombinant antibody techniques were used to construct a RM4/IFN-τ fusion protein containing the chimeric anti-tumor F(ab′)₂ (RM4) and the IFN-τ moiety. The recombinant cDNA of IFN-τ was linked to 3 prime end of the chimeric heavy-chain gene fragment (M4) containing the V_H, the C_HI and the hinge region to form the fused heavy-chain gene fragment M4-IFN-τ. Transfection of the M4-IFN-τ gene fragment into a myeloma derived cell line V_KC_K which produced the chimeric light-chain of the same antibody, allowed the transfectant secreting the bifunctional fusion protein RM4/IFN-τ. The RM4 /IFN-τ was purified by the affinity chromatography. Our data showed that the RM4/IFN-τ retained the TAG72 antigen-binding reactivity as well as the IFN-τ activity as measured in ELISA, FACS analysis of cell-surface TAG72 expression, immunohistochemical study, and up-regulation of cell-surface expression of CEA, HLA class I and class II antigens. Therefore, the bifunctional fusion protein RM4/IFN-τ may prove to be useful in targeting biological effects of the IFN-τ to tumor cells and in this way to stimulate the immune destruction of tumor cells.