Fusogenic membrane glycoproteins as a gene therapy for cancer

Bateman, Andrew R (2003). Fusogenic membrane glycoproteins as a gene therapy for cancer. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f56f

Abstract

Gene therapy strategies hold great promise for the treatment of cancer. This work tests the hypothesis that viral fusogenic membrane glycoproteins (FMG) have potential as cytotoxic gene therapy agents. The truncated, hyperfusogenic form of a C-type retrovirus envelope gene: the Gibbon ape leukaemia virus envelope (GALV), and the F and H genes of the paramyxovirus Measles, were the predominate FMG investigated. Initial studies demonstrated the cytotoxicicty of expressing FMG in tumour cells in vitro. Extensive cell death occured following cell-cell fusion and syncitia formation. Comparison with suicide genes indicated superior cell killing with FMG due to a greater bystander effect. FMG killing induced a stress response with induction and upregulation of heat shock proteins. Detailed analysis of cell death following FMG expression and syncitia formation suggested a non-apoptotic, necrotic mechanism. This was independent of the cell cycle. Viral vectors expressing FMG were developed. There was inefficient production of retroviral vectors based on the Moloney murine leukaemia virus expressing GALV. Improved titre was seen from a lentiviral vector expressing GALV. This vector, when injected intratumourally, was able to eradicate small tumours in nude mice. Adenoviral vectors expressing F and H were produced. Intratumoural injection of these vectors resulted in syncitia formation in vivo. Direct intratumoural injection of an H expressing adenoviral vector into human xenograft tumours expressing Measles F resulted in tumour eradication in 30% of mice. Production of an adenoviral vector expressing GALV required a strategy involving Cre recombinase and a transcriptional silencer to overcome the direct cytotoxicity to producer cells.

Co-expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) with FMG by a number of mechanisms was developed. Their particular in vitro properties were analysed in detail.

In summary this thesis represents the initial studies of a group of genes with their novel application as gene therapy agents for the treatment of cancer. Incorporation of FMG in the development of cytotoxic and immunomodulatory gene therapy strategies hold significant promise and merit further development.