The long range objective of this program is the induction of an effective, cellular immune response to tumors in cancer patients. To achieve this goal, the two phases of the immune system, initiation of a response and its amplification, will be modulated by gene transfer to tumor cells and to specific effector T cells. In the first stage, non immunogenic tumors are rendered immunogenic by the transfection of lymphokine cDNA to explanted tumor cells. Complementary DNAs for I12 and I14 will be used initially. Based on our previous results in preclinical experiments (murine Lewis lung carcinoma), reimplantation of lymphokine producing cells is expected to result in a tumor specific, cellular response in patients. This prediction will be tested in clinical trials of patients suffering from Small Cell Lung Carcinoma (SCLC) and from Melanoma. An episomal plasmid vector system pBMG-Neo allowing high level and stable expression of the gene products will be used for gene transfer in all trials. The induced tumor specific immune response will be evaluated by the clinical response of the patient and by a novel in vivo assay measuring the clearance of subcutaneously administered, radiolabeled and transfected tumor cells. In addition, the frequency of tumor specific effector cells will be determined that can be cultured from the peripheral blood of patients. Cultured tumor specific effector cells will be engineered by gene transfer and used for amplification of the initial cellular response. This stage of gene transfer is aimed at enhancing the effectiveness of T-cells upon reimplantation. The lack of a complete response after lymphokine gene transfer to tumor bearing mice may be due to the downregulation (suppression) of the initially activated effector cells, once they encounter large numbers of non-lymphokine producing (natural) tumor cells. It will be tested whether uncoupling of effector T-cells from normal regulatory controls will improve their efficiency in tumor rejection. These studies will first be carried out in our preclinical Lewis lung cell carcinoma murine model. Cultured tumor specific T-cells will be transfected in order to achieve dysregulated expression of genes known to influence T-cell proliferation (I12 receptor, I12 and I14), T-cell survival (bcl2) and effector function (perforin). The cotransfected HSV thymidine kinase will serve as safety device against uncontrolled T-cell growth.
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