Insertion of the IL-2 gene decreases tumorigenicity of murine fibrosarcoma

Murine interleukin 2 (mIL-2) cDNA was introduced through lipofection into cells of murine F-69-3 fibrosarcoma line established in vitro from tumors induced chemically in athymic mice. Using a modified MTT bioassay in CTLL-2 indicator line the F-69-3/IL-2 transfectants were found to secrete between 650-1750 laboratory units (LU) of IL-2/5 x 10(5) cells/48 h in restricted culture conditions. When inoculated subcutaneously to immunocompetent BALB/c or CD2F1 mice, the transfected cells showed reduced tumorigenic potential as compared with parental F-69-3/wt or control F-69-3/neo cells. The rejection of F-69-3/IL-2 tumors required an intact immune system as they grew progressively in athymic mice. The majority of immunocompetent mice that rejected IL-2 secretors were found to be protected against subsequent challenge with parental cells. These preliminary results suggest that IL-2-transfected murine fibrosarcoma could be used as a model for studying mechanisms underlying the antitumor immune response.