No abstract

This recombinant expression vector can be used as a gene therapy vector for HCC. The expression of tumor killing gene will be confined within the site of tumor and the activity of which can be regulated by retinoic acid.

AIM:To construct an eukaryotic superantigen gene expression vector containing the recombinant gene of SEA and CD80 molecule transmembrane region (CD80TM), and to express staphylococcus enterotoxin A (SEA) on the membrane of hepatocellular carcinoma (HCC) cell to form a superantigen gene modified tumor vaccine for HCC. METHODS:SEA and linker-CD80TM gene were amplified through PCR from plasmid containing cDNA of SEA and CD80. Gene fragments were then subcloned into the multiple cloning sites of retroviral vector pLXSN. Recombinant plasmid was transferred into HepG2 cells mediated with lipofectamine, positive clones were selected in culture medium containing G418. RT-PCR and indirect immunofluorescence studies confirmed that SEA was expressed specifically on HCC cell membrane. INFγ-ELISPOT study demonstrated that SEA protein was expressed on the membrane of HCC cells. Cytotoxicity of HepG2-SEA primed CTLs (SEA-T) was analyzed by 51 Cr release assay. T cells cultured with rhIL-2 (IL-2-T) were used as control. RESULTS:Restriction digestion and sequence analyses confirmed the correctness of length, position and orientation of inserted fusion genes. SEA was expressed on the surface of HepG2 cells, HepG2-SEA had strong stimulating effect on production of HepG2 specific CTL (P<0.001). SEA-T had enhanced cytotoxicity to HepG2 cells (P<0.05). CONCLUSION:Tumor cell membrane expressed superantigen can be used to reinforce the immune effect of tumor cell vaccine for HCC, which provides a new method of the enhanced active immunotherapy for HCC.

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.

No abstract