INCREASE OF CYTOTOXIC SENSITIVITY OF PRIMARY HUMAN-MELANOMA CELLS TRANSFECTED WITH THE INTERLEUKIN-7 GENE TO AUTOLOGOUS AND ALLOGENEIC IMMUNOLOGICAL EFFECTOR-CELLS

Patients with metastatic melanoma have a very poor prognosis. In many cases, the tumor recurs after surgical excision. Therefore, it might b e beneficial for cancer patients to induce an immune attack against th e tumor by inserting a cytokine gene into the tumor cells. Here, 14 pr imary cell cultures could be established from 45 patients with maligna nt melanoma. Primary cell cultures were transfected via electroporatio n with the gene encoding for human interleukin-7 (IL-7). Transfection resulted in the production of biologically active IL-7 with an average of 850 pg/mL per 10(6) cells per 24 hours. Irradiation with 10,000 cG y, which inhibited tumor cell growth in vitro, increased the amount of released IL-7 to an average amount of 1050 pg/mL per 10(6) cells per 24 hours. No significant differences in the phenotype were observed in the IL-7-transfected cells compared with nontransfected cells. The ex pression of HLA class I and II, ICAM-1, and of a melanoma-associated a ntigen remained unaltered. Transfection with IL-7 had no significant e ffect on the proliferation of melanoma cells as measured in a MTT -(4, 5-dimethylthiazol-2-yl)-2,5-diphenltetrazolium bromide] assay. There w as no significant change in the cytokine profile after transfection or irradiation of the cells, but one cell culture expressed a high amoun t of IL-6 (about 2 ng/mL). IL-6 was expressed in nontransfected cells and was not altered by transfection. interestingly, transfected cells from primary melanoma cultures possessed a higher sensitivity to immun ologic effector cells compared with nontransfected cells. This was tru e for allogeneic as well as autologous melanoma cells. Our results sho w the feasibility of a gene transfer into primary human melanoma cells , different from retroviral transduction. IL-7-transfected cells might be of value in vaccination protocols for melanoma patients.