Construction of a regulable gene therapy vector targeting for hepatocellular carcinoma

AIM: To construct a gene modified hepatocellular carcinoma (HCC) specific EGFP expression vector regulated by abbreviated cis-acting element of AFP gene.METHODS: The minimal essential DNA segments of AFP gene enhancer and promoter were synthesized through PCR from Genome DNA of HepG2 cells. Gene fragments were then cloned into the multiple cloning site of non-promoter EGFP vector pEGFP-t. Recombinant plasmid was transferred into positive or negative AFP cell lines by means of lipofectamine. The expression of EGFP was tested by fluorescence microscope and flow cytometry. The effect of all-trans retinoic acid (ATRA) on the expression of EGFP was tested in different concentrations.RESULTS: By the methods of restriction digestion and sequence analyses we confirmed that the length, position and orientation of inserted genes of cis-acting element of AFP were all correct. The transcription of EGFP was under the control of AFP cis-acting element. The expressing EGFP can only been detected in AFP producing hepatoma cells.The expression rate of EGFP in G418 screened cell line was 34.9±4.1%. 48 h after adding 1×10-7M retinoic acid, EGFP expression rate was 14.7±3.5%. The activity of AFP gene promoter was significantly suppressed by addition of 1×10-7M retinoic acid (P＜0.05, P=0.003, t=6.488).CONCLUSION: 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.

Superantigen-SEA gene modified tumor vaccine for hepatocellular carcinoma:An in vitro study

AIM: To construct an eukaryotic superantigen gene expression vector containing the recombinant gene of SEA and CD80 molecule transmembrane region (CD80TM), and to expresss taphylococcus 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. INFT-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^51Cr 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 superarfdgen 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.