COMBINATION EFFECT OF VACCINATION WITH IL2 AND IL4 CDNA TRANSFECTED CELLS ON THE INDUCTION OF A THERAPEUTIC IMMUNE-RESPONSE AGAINST LEWIS LUNG-CARCINOMA CELLS

In order to develop a more effective method of immunotherapy we have transfected mouse interleukin-2 (IL2) or mouse interleukin-4 (IL4) cDNA into a spontaneous non-immunogenic murine lung cancer, Lewis lung carcinoma (LLC). IL2 cDNA transfection more strongly decreases tumorigenicity of LLC than IL4 cDNA transfection. Recombinant-human-IL2 treatment of mice that were transplanted with untransfected LLC could not prolong their survival. In contrast, vaccination with IL2-cDNA-transfected LLC (LLC-IL2) and LLC-IL2 mixed with IL4-cDNA-transfected LLC (LLC-IL4) could significantly suppress tumor growth of LLC in a tumor-specific manner. The vaccination with LLC-IL2 mixed with the same number of LLC-IL4 cells was more suppressive to the growth of LLC than that with LLC-IL2 cells alone, while LLC-IL4 vaccination alone was ineffective. Nude, severe-combined-immune-deficient (SCID) and beige mice were unable to reject LLC-IL2 cells. However, immunodeficient mice responded to LLC-IL2, but not to LLC, since their survival times after transplantation with LLC-IL2 cells were significantly longer than the survival time of normal or immunodeficient mice transplanted with untransfected LLC cells. We conclude that vaccination with IL2-producing tumors and, with more pronounced effect, in combination with IL4-producing tumors, is able to induce an immune response to this normally non-immunogenic tumor. Tumor rejection appears to be achieved by the combined activity of CTL and NK cells. This strategy has potential for new immunotherapeutic interventions in cancer patients.