Suppression of tumor formation and induction of natural killer cell activity in BALB/c nude mice by human B7-1 (CD80) gene transfer subcutaneously injected with human hepatocellular carcinoma cells (Huh-7)

BACKGROUND/AIMS: Immunogene therapy is extensively studied for a therapeutic modality of various cancers. This study was conducted to investigate the efficacy of immunogene therapy using the T-cell costimulatory molecule and human B7-1 (CD80, hB7-1) in an in vivo human hepatocellular carcinoma (HCC) model. METHODS: The stable HCC cell line expressing hB7-1 gene was established using retroviral vector (Huh-7/hB7-1). Of fourteen BALB/c nude mice, 7 were subcutaneously injected with 2 X 10(6) Huh-7/hB7-1 cells, while the other 7 were injected with 2 X 10(6) Huh-7/mock cells as a control group. After the injection, the mice were observed weekly for three months for subcutaneous tumor formation. Assay for natural killer (NK) cell cytotoxicity and serum IFN-gamma was performed at 1 and 2 weeks after inoculation. RESULTS: In BALB/c nude mice inoculated with Huh-7/hB7-1 cells, no tumor growth was observed. BALB/c nude mice inoculated with Huh-7/hB7-1 cells showed significantly increased NK cell activities of splenocytes compared with those with Huh-7/mock cells. Serum IFN-gamma was not measurable at 1 week, but significantly increased at 2 weeks after inoculation to the level of 470 pg/ml in BALB/c nude mice with Huh-7/mock cells and 521 pg/ml in BALB/c nude mice with Huh-7/hB7-1. CONCLUSIONS: Our results demonstrate the in vivo anti-tumor immunity and NK cell activation by transfer of hB7-1 gene into human HCC in xenogeneic BALB/c nude mice model. This approach may provide a tool for the development of immunogene therapies against human malignant tumors.