A synergistic antitumor effect of interleukin-2 addition with CD80 immunogene therapy for peritoneal metastasis of gastric carcinoma.

The co-stimulatory molecule CD80 is a ligand of CD28, which plays a key role in the induction of cell-mediated immune responses. Many tumors, including gastric cancer, decrease the expression of CD80, which results in the failure of immune recognition. We evaluated the effect of interleukin-2 addition combined with CD80 infection on the peritoneal metastasis in gastric cancer. CD80 infection combined with interleukin-2 addition significantly increased the activated cytotoxicity of mononuclear cells compared to CD80 gene infection and compared to the lacZ control group. In vivo, the survival of animals with intraperitoneal tumor was longest in those given CD80 infection with interleukin-2 addition (median survival, 46 days), followed by those given interleukin-2 (39 days), those given CD80 infection (37 days), and those given lacZ (29 days). These results suggest that interleukin-2 addition might contribute to improving the observed outcome of CD80 immunogene therapy in peritoneal metastasis of gastric carcinoma.