Induction of Antitumor Response by In Vivo Allogeneic Major Histocompatibility Complex Gene Transfer Using Electroporation

BackgroundMost malignancies lack tumor-associated antigens, which are recognized by T-lymphocytes through major histocompatibility complex (MHC) molecules, and seem to evade host immunological defense. In this study, we investigated whether allogeneic MHC gene transfer into the low-antigenic tumor might induce cell-mediated immunity, and provide an immunotherapeutic effect in vivo.Materials and methodsMammary adenocarcinoma cells (MAT B III) originated from an F344 rat (RT1Al) were transfected with a plasmid DNA encoding RT1Aa (pcMRT1A) in vitro. Cytolytic T-cell response was then evaluated using F344 splenocytes. Furthermore, pcMRT1A–liposome complex was injected into the MAT B III tumors grown in F344 rats, followed by a series of eight electrical pulses with a electroporator, every other d for total of four times. The tumor size and survival of animals were evaluated thereafter.ResultsThe expression of RT1Aa on the tumor cells induced cytolytic T-cell response in vitro. Intratumor injection of pcMRT1A-liposome complex followed by in vivo electroporation markedly generated biological response, including increased interferon-γ (IFN-γ) expression and a large number of infiltrated cells in the tumor. Inhibited tumor growth, even complete tumor regression, was observed, resulting in prolonged survival time.ConclusionsDirect transfer of allogeneic MHC gene into the tumor by in vivo electroporation could induce a cell-mediated immune response against the introduced antigens, resulting in local IFN-γ production. This initial response may bring about the subsequent immunological response even to the unmodified tumor cells through cytokines such as IFN-γ, resulting in the marked tumor regression.