Characterization of genetically altered, interleukin 2-independent naturalkiller cell lines suitable for adoptive cellular immunotherapy

NK-92 is a highly cytotoxic natural killer (NK) tumor cell line that posses ses properties that make it an excellent candidate for adoptive cellular im munotherapy. However, the cytotoxicity of NK cells is dependent on cytokine s such as interleukin 2 (IL-2). Although NK-92 cells maintain cytotoxicity for a time after withdrawal of IL-2, clinical use will probably require pro longed treatment with fully activated cells to eliminate disease effectivel y. The ability to support cytotoxic cells with exogenously administered IL- 2 is limited by associated toxicity. Therefore, we describe the transfectio n of the IL-2-dependent NK-92 cell line with human IL-2 (hIL-2) cDNA by par ticle-mediated gene transfer to create two IL-2-independent variants, NK-92 MI and NK-92 CI, and describe their characterization and comparison with pa rental cells. Both variants were shown to contain, express, and synthesize the hIL-2 cDNA. IL-2 synthesis was higher in NK-92MI cells compared with NK -92CI cells, with no expression in parental cells. Functionally, the cytoto xicity of all three cell lines was similar and coincubation with IL-2-indep endent variants did not affect hematopoietic progenitor cells. NK-92MI and NK-92 CI cells were more radiosensitive than NK-92 cells, with proliferatio n inhibited at lower radiation doses and increased morality and decreased c ytotoxicity compared with parental cells. Data presented here show that we have created by particle-mediated gene transfer two IL-2-independent varian ts of NK-92 that are identical to parental cells in virtually all respects, including high cytotoxic activity. The nonviral transfection of these cell s makes them suitable for clinical applications. These IL-2-independent cel ls should allow prolonged treatment with fully active natural killer cells without the need for exogenous IL-2 support.