IL-2 gene-transduced human HLA-A2 melanoma cells can generate a specific antitumor cytotoxic T-lymphocyte response.

This study was designed to assess whether transfer of the interleukin-2 (IL-2) gene into human tumor cells could generate cytotoxic T lymphocytes (CTL) directed specifically against the autologous tumor. Two HLA class I+ melanoma cell lines, one (TOM) A2+ and the other (CLB-M) A2-, obtained from living patients were transduced with the IL-2 gene. The patients' peripheral blood lymphocytes (PBL) were incubated with irradiated IL-2 gene-transduced autologous tumor cells for up to four weeks. After seven days, PBL from both patients showed non-specific cytotoxic activity against the K562 cell line. When the co-culture incubation time was prolonged to 28 days, PBL from patient TOM (A2+) developed a lytic activity directed specifically against the autologous tumor cells. In contrast, after 28 days of incubation, PBL from CLB-M (A2-) displayed only non-specific cytotoxic activity. Inhibition experiments demonstrated that the specific lytic function observed with TOM cells transduced with the IL-2 gene could be reversed following incubation with monoclonal antibodies directed against HLA class I and CD8. The evidence that K562 cells were incapable of blocking the PBL killing capacity in a cold-target inhibition assay further confirmed that engineered TOM cells induced the generation of specific CTL. This study indicates that retroviral vector mediated transfer of the IL-2 gene into human melanoma cell lines can lead to the amplification of the autologous cytotoxic compartment and to the generation of specific antitumor CTL, and that the A2 allele may play an important role in the process of tumor recognition.