The combination of a chemokine, cytokine and TCR-based T cell stimulus for effective gene therapy of cancer.

Cytotoxic T cells can recognize and kill tumor cells that present peptides derived from tumor-associated antigens (TAA) on their surface when associated with major histocompatibility complex (MHC) class I molecules. However, immune responses to tumor-associated antigens are often suppressed by a tumor-induced state of immune anergy. Previous work has attempted to overcome tumor-induced T cell anergy by the direct injection of vectors carrying genes encoding one of a variety of cytokines. Polyclonal stimulation of T cells, preferably via the TCR complex, results in a cascade of cytokines associated with T cell activation and thus may be better able to overcome T cell anergy. We have previously reported the use of the highly attenuated MVA poxvirus to express on tumor cells, in vitro and in vivo, antibodies specific for the CD3epsilon chain (KT3). When injected into growing tumors, these constructs induce the activation of immune effector cells and result in rejection of the tumor. A variety of recombinant adenovirus (Ad) vectors expressing immunostimulatory and/or immunoattractant molecules have now been produced. With this collection of viruses, we have carried out in vivo analyses of combinations of vectors in tumor therapy experiments. For example, we have tested, in murine tumor models, the combination of MVA-KT3 with Ad expressing recently identified cytokines [for example interleukin-12 (IL-12), IL-18] as well as chemokines (e.g. RANTES, MIP1beta). One combination, MVA-KT3/Ad-IL-12/Ad-MIP1beta causes rejection of 100% of growing RENCA tumors. Much attention has been focused on cancer gene therapy using gene transfer of single agents. These data show that antigenic stimulation via the MHCI/TCR-CD3+cytokine+chemokine combination may provide a new and promising approach to cancer gene therapy which is more likely to bypass tumor immunosuppression mechanisms.

Improvement of adoptive cellular immunotherapy of human cancer using ex-vivo gene transfer.

A variety of adoptive cellular strategies, aimed at boosting the immune system, have been tested in the management of metastatic diseases. Despite the drawbacks associated with ex vivo cell manipulation and upscaling, several such approaches have been assessed in the clinic. The use of lymphokine-activated killer (LAK) cells, auto-lymphocyte therapy (ALT) and tumor-infiltrating lymphocytes (TIL) have been the best studied and further trials are ongoing. Thus far, these approaches have not consistently shown benefit when compared to standard immune-based treatment with biologic response modifiers, notably, high-dose interleukin-2 (IL-2). More recently, it has been shown, in various animal models, that the ex vivo transfer of genes to cells of the immune system can have a dramatic impact on cancer immunotherapy. The application of gene transfer techniques to immunotherapy has animated the field of cell-based cancer therapy research. A wide variety of viral and non-viral gene transfer methods have been investigated in this context. Ex vivo strategies include gene delivery into tumor cells and into cellular components of the immune system, including cytotoxic T cells, NK, macrophages and dendritic cells (DC). Several of these approaches have already been translated into cancer therapy clinical trials. In this review, we focus on the rationale and types of ex vivo gene-based immunotherapy of cancer. Finally, the use of genetically modified DC for tumor vaccination and its prospects are discussed.

Tumor gene therapy by MVA-mediated expression of T-cell-stimulating antibodies.

Immune responses to tumor-associated antigens are often dampened by a tumor-induced state of immune anergy. Previous work has attempted to overcome tumor-induced T-cell anergy by the direct injection of vectors carrying the genes encoding one of a variety of cytokines. We hypothesised that the polyclonal stimulation of T cells, preferably through the TCR complex, would result in a cascade of cytokines associated with T-cell activation and would be best able to overcome T-cell anergy. Here we use the highly attenuated MVA poxvirus to express on tumor cells, in vitro and in vivo, either of three membrane-bound monoclonal antibodies specific for murine TCR complex. Using this system, we have expressed antibodies specific for the CD3 epsilon chain (KT3), TCR alpha/beta complex (H57-597), and V beta 7 chain (TR310). Tumor cells bristling with these antibodies are capable of inducing murine T-cell proliferation and cytokine production. When injected into growing tumors (P815, RenCa, and B16F10), these constructs induce the activation of immune effector cells and result in the rejection of the tumor. Histological and FACS analysis of tumor-infiltrating leukocytes reveal that the injection of recombinant virus-expressing antibodies specific for the TCR complex attracts and activates (CD25(+), CD69(+)) CD4 and CD8 lymphocytes. This approach represents a novel strategy to overcome T-cell anergy in tumors and allow the stimulation of tumor-specific T cells.