THE IN-VITRO EFFECTS OF INTERLEUKIN-12 UPON TUMOR-INFILTRATING LYMPHOCYTES DERIVED FROM RENAL-CELL CARCINOMA

Clinical trials utilising interleukin (IL)-2 with tumor-infiltrating l ymphocytes (TIL) have demonstrated efficacy in the treatment of metast atic renal cell carcinoma (RCC). Several cytokine's, as well as growth factors have demonstrated modulatory effects upon the biological prop erties of TIL from RCC, suggesting a potentially important role for cy tokines other than IL-2 in the development of active and tumor-specifi c TIL. IL-12 was recently characterized as a natural-killer-cell-stimu latory factor or cytotoxic-T-cell-maturation factor. These properties of IL-12 prompted us to investigate the impact of this cytokine upon t he activation of TIL from human RCC. In an attempt to enhance the in v itro growth and activity of renal TIL, we have grown eight renal TIL c ultures in varying concentrations of IL-2 (8, 40, 80, 400 U/ml) and IL -12 (200 U/ml). In addition, IL-12 (200 U/ml) was added to TIL culture s pre-activated with IL-2 (400 U/ml). Growth, cell expansion, and the ability of TIL to release certain cytokines upon tumor stimulation wer e determined. Proliferation assays, phenotypic analysis, and cytotoxic ity assays were performed at an early and a late culture stage. IL-12, alone and when added to suboptimal concentrations of IL-2, failed to induce TIL growth. While the addition of IL-12 to optimal doses of IL- 2 suppressed TIL culture expansion, sequential culture exposure first to IL-2 and then to IL-2 + IL-12 increased the number of cells express ing CD3(+)/CD56(+) and these cultures demonstrated enhanced in vitro l ysis of autologous tumor. IL-12 clearly demonstrated a sequence-depend ent impact of the biological behaviour of TIL from RCC. The optimal us e of IL-12 in the in vitro expansion of renal TIL may result in cells with an enhanced specific anti-tumor effect.