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RESEARCH PRODUCT

Gene Therapy of Human Melanoma — from Animal Experiments to the Clinical Trial

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Low immunogenecity of tumour cells is one of the reason that specific immune response is insufficient to destroy malignant cells. In an attempt to augment weakly immunogenic B78H1 mouse melanoma cell line, these cells were transfected with genomic DNA from a line of human melanoma cells expressing a 96kD melanoma associated antigen (MAA) that is intercellular adhesion molecule 1 (ICAM 1). The transfected cells expressed fivefold higher quantities of the melanoma associated antigen from which the DNA was obtained. Human ICAM 1 expressed by mouse melanoma cells appeared to be highly immunogenic leading to the rejection of the modified mouse melanoma cells. The transfected cells appeared to be more immunogenic than nontransfected ones leading to their rejection. Unfortunately, in this experimental system generated specific and nonspecific immune response against heterologous antigen, which is human ICAM 1 was not sufficient enough to prevent growth of parental tumour cells. In the preclinical studies B78H1 murine melanoma cells were stable transfected with cDNAs coding for human IL6, murine sIL6R (soluble IL6 receptor) and human leukaemia inhibitory factor (LIF). The parental and transfected melanoma cells were i.v. or s.c. injected into C57BL/6xC3H and SCID CB17 mice. Whereas B78H1 cells formed tumours and lung metastasis in injected animals, transfected cells showed greatly reduced tumour and metastasis formation. Transfection of IL6, sIL6R or LIF had similar protective effects. The combination of IL6 and sIL6R was most effective.Subsequent s.c. challenge of transfected melanoma cells into animals initially injected i.v. with B78H1 control cells resulted in a reduction of lung metastasis and increased survival time. The results obtained from animal experience indicated that sIL6R gene transferred into melanoma cells inhibits their growth, and their ability to metastasise. In the clinical trial HLA-A1 and/or HLA-A2-positive patients with melanoma were immunized with an admixture of autologous tumour cells and allogeneic melanoma cells genetically engineered to secrete IL6 and sIL6R in order to elicit or enhance specific and non-specific anti-melanoma immune responses to autologous tumour cells. The obtained preliminary result indicate on increase of involvement of CD8+ and CD4+ T cells infiltrating melanoma lesions. Immunophenotyping of peripheral blood lymphocytes with panel of specific monoclonal antibodies showed increase of lymphocytes expressing activation markers, i.e. HLA-DR and CD25 (interleukin 2 receptor). In the cytotoxicity assay using K562 cells as well as some melanoma cell lines, it was shown that “anti-cancer vaccine” may result in enhancement of NK and cytotoxic T lymphocyte responses after subsequent immunization of melanoma patients. The provisional conclusion is that “anti-cancer vaccine” may enhance unspecific and specific anti-tumour immune response in some of the treated malignant melanoma patients.