Regression of established murine adenocarcinoma by in vivo allogeneic MHC gene transfer using electroporation and modification of donor MHC antigens by antisense gene transfer to prevent rejection of transplanted organs

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1. In our first study, we investigated immunogenicity of low-antigenic rat adenocarcinoma cells after transfection with an allogeneic class I major histocompatibility complex (MHC) gene in vitro, and studied whether direct allogeneic MHC gene transfer into the established tumor using in vivo electroporation might stimulate the host immune response, and also provide an immunotherapeutic effect. Mammary adenocarcinoma cells (MAT B III) originated from F344 rat (RT1AィイD11ィエD1) were transfected with a plasmid DNA encoding RT1AィイD1aィエD1 (pcMRT1A) in vitro. The expression of RT1AィイD1aィエD1 antigen on the tumor cells resulted in stimulating cytolytic T-cell response against specific gene products. Furthermore, we investigated the antitumor effects of direct allogeneic MHC class I gene transfer into the tumor grown in the syngeneic host using in vivo electroporation. Intratumoral injection of the pcMRT1A-Lipofectin complex followed by eight electrical pulses (99μsec, 400V/cm) through two electr … More odes located on each side of the tumor induced a marked regression in tumor growth and prolonged survival periods of the host. These results indicate that transferring allogeneic class I MHC gene directly into tumor using in vivo electroporation could induce a cell-mediated immune response and provide an immunotherapeutic effect for the established tumor.2. In our second study, we examined whether insertion of an antisense vector into the allograft could down-regulate the expression of the target antigens and to prevent the rejection of transplanted organs. In vitro study, down-regulation of donor MHC class I antigen expression on the donor cells was observed after transfection of plasmid vector containing antisense of donor target antigen in vitro and also immunological response to these cells. However, in vivo, efficient transfection of antisense DNA to the donor graft organ was very difficult at present. Now we are developing new technology to provide for efficient in vivo transfection. Less