In vivo tumor co-transfection with superantigen and CD80 induces systemic immunity without tolerance and prolongs survival in mice with hepatocellular carcinoma.

Background: Since transfection of established tumors with immunostimulatory genes can elicit antitumor immunity, we treat mouse HCC with in vivo transfection of superantigen SEA and/or costimulatory molecule CD80 and evaluated the safety and efficacy.

Methods: Mice with HCC were treated with lipid-complexed plasmid DNA encoding staphylococcal enterotoxin A and/or CD80. Then the mice were evaluated for tumor regression, systemic immunologic responses, survival times and treatment-associated toxicity.

Results: Of all treated mice, the overall response rates (complete or partial remission) for SEA, CD80 and SEA/CD80 treated mice in this study were 65%, 60% and 75% separately, and were significantly higher than that of untreated mice. Most of the treat mice completed the therapy without any significant reaction. CTL activity increased with time of treatment and correlated temporally with an objective tumor response. Also our results indicated that local intratumoral expression of SEA did not lead to detectable deletion or anergy of SEA-reactive spleen T cells. Survival times for hepatoma mice in this study treated by intratumoral injection of SEA, CD80 and SEA/CD80 were prolonged significantly (P < 0.01) compared with the control mice.