Antitumor response of genetically engineered IL-2 expression to human esophageal carcinoma cells in mature T cell-defective condition

We examined whether antitumor effect could be produced by retrovirally expr essed human interleukin-2 (hIL-2) gene in human esophageal cancer cells (T. Tn) using immunocompromised nude mice. Loss of tumorigenicity of hIL-2-prod ucing T.Tn (T.Tn/hIL-2) cells inoculated subcutaneously was observed in con trast to continuous tumor growth of wildtype cells, although in vitro proli feration of T.Tn/hIL-2 cells remained the same as that of wild-type cells. The antitumor effect was also evidenced by the injection of T.Tn/hIL-2 cell s into established tumors of wild-type cells. The injection significantly r etarded the subsequent growth of wild-type tumors. Histological examination of regressing T.Tn/hIL-2 cells revealed necrotic areas and infiltration of several types of inflammatory cells. Treatment of nude mice with anti-asia loGM(1) antibody did not influence the IL-2-mediated tumor rejection. Vacci nation of nude mice with irradiated T.Tn/hIL-2 cells whose secretion of hIL -2 in amount was comparable to that of unirradiated cells did not develop p rotective immunity. Taken together, the antitumor effect achieved in nude m ice by the inoculation of T.Tn/hIL-2 cells is mediated by non-T non-natural killer cells.