Co-transfer of human wild-type p53 and granulocyte-macrophage colony-stimulating factor genes via recombinant adenovirus induces apoptosis and enhances immunogenicity in laryngeal cancer cells

Recombinant adenoviral vector expressing human wild-type p53, GM-CSF, and B7-1 genes suppresses the growth of glioma in vivo

Malignant gliomas are the most common of primary brain tumors and have been proven incurable with conventional treatments. Evidence have shown that a recombinant adenoviral vector expressing human wild-type p53, granulocyte-macrophage colony-stimulating factor (GM-CSF), and B7-1 genes (BB-102) may have antitumor effects in vitro. In this study, we investigated the effects of BB-102-based vaccine on glioma in vivo. An animal model using nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice with human immune system was established. The mice were vaccinated with inactivated U251 glioma cells transduced with BB-102 or adenoviral vector expressing green fluorescence protein (Ad-GFP) as a control and followed by the challenge of live U251 glioma cells. Tumor growth and antitumor responses were measured. Data showed that mice vaccinated with BB-102 had significantly reduced local tumor growth compared to mice with Ad-GFP vaccination or the control group. Histopathological analysis displayed low tumor cell density and significant infiltration of human peripheral blood lymphocytes (HuPBLs) in the tumor tissues of mice transduced with BB-102. Immunohistochemical analysis showed that mutant p53 was not expressed in tumor tissues of mice with BB-102 vaccination, and the expression level of Ki67 was significantly lower in the tumor tissues of the BB-102 group than those in the Ad-GFP group or the control group. Further study demonstrated that mice with BB-102 vaccination had significantly increased total T cell numbers, total T cell proportion, CD4+ T cell proportion, and CD8+ T cell proportion in spleens, as well as higher value of IgG, IgA, and IgE in sera. These data suggest that the recombinant adenoviral vector expressing human wild-type p53, GM-CSF, and B7-1 genes could suppress glioma in NOD/SCID mice model and might be considered as a novel strategy for glioma therapy.

Adenovirus mediated transfer of p53, GM-CSF and B7-1 suppresses growth and enhances immunogenicity of glioma cells

OBJECTIVES

Malignant gliomas are good targets for gene therapy because they have been proven incurable with conventional treatments. However, malignant gliomas are genetically and physiologically highly heterogeneous, and current gene therapy interventions have been designed to target only a few variations of this kind of disease. Hence, we developed a combined gene therapy approach using a recombinant adenovirus carrying human wild-type p53 (WT-p53), granulocyte-macrophage colony-stimulating factor (GM-CSF) and B7-1 genes (designated BB-102) to combat the disease.

METHODS

Human malignant glioma cells U251 and U87 were transduced with BB-102. Expression of WT-p53, GM-CSF and B7-1 genes were determined by Western blot, enzyme linked immunosorbent assay and flow cytometric analysis, respectively. Growth rates were determined by serial cell counts. Apoptosis was detected by flow cytometric analysis. Proliferation of autologous peripheral blood lymphocytes (PBLs) and cytotoxicity against primary glioma cells were assessed by cell proliferation and cytotoxicity assay kits, respectively.

RESULTS

By the transduction of BB-102, high expression levels of the three exogenesis genes were detected in glioma cells. Cell growth was inhibited and apoptosis was induced. Significant proliferation of autologous PBLs and specific cytotoxicity against primary glioma cells were also induced by the infection of BB-102 in vitro, with the effect being more evident than that of Ad-p53.

CONCLUSION

These results suggest that glioma cell vaccination co-transferred with p53, GM-CSF and B7-1 genes may be a feasible and effective immunotherapeutic approach in glioma treatments.

Modification of HPV 16 E7 genes: correlation between the level of protein expression and CTL response after immunization of C57BL/6 mice

Immunization with a codon-optimized HPV 16 E7 gene was shown to yield higher levels of E7-specific cytotoxic T cells [Liu WJ, Gao F, Zhao KN, Zhao W, Fernando GJ, Thomas R, et al. Codon modified human papillomavirus type 16 E7 DNA vaccine enhances cytotoxic T-lymphocyte induction and anti-tumour activity. Virology 2002;301:43]. Here, we sought to verify the hypothesis that there is a direct correlation between the level of protein expression and immunogenicity in mice. We generated HPV 16 E7 expression plasmids where the genes were inserted either as authentic sequence (wt) or after optimizing the codons for use in mammalian cells (opt). For enhancement of translation of the E7 gene a 5' Kozak sequence (K) was added. Transfection experiments revealed the strength of expression in the order of E7opt+K, E7opt-K, E7wt+K and E7wt-K. After immunization of C57/B6 mice we observed an equally strong CD8+T-cell response with the E7opt plasmids (+ or -K), followed by the E7wt+K and E7wt-K DNAs. The same difference in efficiency was obtained in tumor protection experiments. Regression of pre-existing tumors and CTL activity was observed only with the E7opt+K plasmid. From these data, we conclude that the level of protein expression correlates with the efficiency of CTL response and hence testing by transfection of cells in culture may allow a pre-selection of expression plasmids prior to DNA immunization.

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Synergetic anticancer effect of combined quercetin and recombinant adenoviral vector expressing human wild-type p53, GM-CSF and B7-1 genes on hepatocellular carcinoma cells in vitro

AIM: This study investigated the anti-cancer effect of combined quercetin and a recombinant adenovirus vector expressing the human p53, GM-CSF and B7-1 genes (designated BB-102) on human hepatocellular carcinoma (HCC) cell lines in vitro.

METHODS: The sensitivity of HCC cells to anticancer agents was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The viability of cells infected with BB-102 was determined by trypan blue exclusion. The expression levels of human wild-type p53, GM-CSF and B7-1 genes were determined by Western blot, enzyme-linked immunosorbent assay (ELISA) and flow cytometric analysis, respectively. The apoptosis of BB-102-infected or quercetin-treated HCC cells was detected by terminal deoxynucleotidyl transferase (TdT) assay or DNA ladder electrophoresis.

RESULTS: Quercetin was found to suppress proliferation of human HCC cell lines BEL-7402, HuH-7 and HLE, with peak suppression at 50 μmol/L quercetin. BB-102 infection was also found to significantly suppress proliferation of HCC cell lines. The apoptosis of BB-102-infected HCC cells was greater in HLE and HuH-7 cells than in BEL-7402 cells. Quercetin did not affect the expression of the three exogenous genes in BB-102-infected HCC cells (P > 0.05), but it was found to further decrease proliferation and promote apoptosis of BB-102-infected HCC cells.

CONCLUSION: BB-102 and quercetin synergetically suppress HCC cell proliferation and induce HCC cell apoptosis, suggesting a possible use as a combined anti-cancer agent.

Growth suppression and immunogenicity enhancement of Hep-2 or primary laryngeal cancer cells by adenovirus-mediated co-transfer of human wild-type p53, granulocyte-macrophage colony-stimulating factor and B7-1 genes

Co-transfer of immunomodulatory and antiproliferative genes may be the basis for new strategies to potentiate tumor regression. In this study, we evaluated the in vitro effect of the introduction of human wild-type p53, granulocyte-macrophage colony-stimulating factor (GM-CSF), and B7-1 genes via recombinant adenovirus on the growth and immunogenicity of Hep-2 or primary laryngeal cancer cells. By the introduction of wild-type p53 gene, the growth of Hep-2 cells was inhibited via enhanced apoptosis. By the introduction of GM-CSF and B7-1 genes, the immunogenicity of cancer cells was enhanced. Significant proliferation of tumor infiltrating lymphocytes (TILs) and tumor-specific cytotoxicity of cytotoxic T lymphocytes (CTLs) were induced in vitro. Furthermore, the combinative effect of GM-CSF and B7-1 was even more evident than that of any one of them singly. These results suggest that the co-transfer of human wild-type p53, GM-CSF and B7-1 genes into tumor cells via recombinant adenovirus may be further developed into a potential combination gene therapy strategy for cancer.