Objectives: To investigate whether tumor-infiltrating lymphocytes (TILs) transfected with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and interleukin-2 (IL-2) genes are capable of improving the potency and efficacy of propagation and cytotoxicity against renal cell carcinoma (RCC) cells in vitro.
Methods: A mammal expression vector system was constructed. TILs were transfected by liposome-mediated gene transfection. The degree of cytokine mRNA expression was evaluated with Northern blot. Protein expression was determined with Western blot and enzyme-linked immunosorbent assay. Cytotoxicity of TILs against autologous RCC cells and the human RCC cell line (786-0) were examined by chromium release assay. Flow cytometric analyses were performed to determine the apoptosis of tumor cells.
Results: A high level of expression of the human TRAIL and IL-2 stable transfected TILs was observed. The mean IL-2 production was 22.6 +/- 5.2, 507.7 +/- 52.4, and 549.0 +/- 74.0 ng/10(6) cells/24 hours in the TIL/parental, TIL/IL-2, and TIL/TRAIL+IL-2 genes, respectively. The mean cytotoxicity (effector/target ratio 20:1) of TIL/parental, TIL/IL-2, TIL/TRAIL, and TIL/TRAIL+IL-2 against autologous RCC cells in the percentage of cytolysis was 21.2% +/- 4.8%, 32.1% +/- 5.5%, 63.5% +/- 6.6%, and 78.1% +/- 9.63%, respectively. These four groups showed cytotoxic activity against allogeneic 786-0 RCC cells; the corresponding values were 9.8% +/- 3.5%, 12.3% +/- 3.4%, 24.1% +/- 4.9%, and 30.4% +/- 6.2%. The number of apoptotic cells was significantly greater for autologous RCC cells than for 786-0 cells after TIL/TRAIL and TIL/TRAIL+IL-2 treatment.
Conclusions: TIL/TRAIL+IL-2 and TIL/IL-2 were expanded by autocrine IL-2. TIL/TRAIL+IL-2 and TIL/TRAIL showed significant cytotoxicity that was induced by TRAIL. TILs, including parental TILs and transfected TILs, demonstrated a potent cytotoxicity against RCC cells with remarkable selectivity. Autologous RCC cells seemed more sensitive than allogeneic RCC cells.