Abstract
BackgroundGlioblastoma multiforme is the most malignant cancer of the brain and is notoriously difficult to treat due to the highly proliferative and infiltrative nature of the cells. Herein, we explored the combination treatment of pre-established human glioma xenograft using multiple therapeutic genes whereby the gene expression is regulated by both cell-type and cell cycle-dependent transcriptional regulatory mechanism conferred by recombinant HSV-1 amplicon vectors.ResultsWe demonstrated for the first time that Ki67-positive proliferating primary human glioma cells cultured from biopsy samples were effectively induced into cell death by the dual-specific function of the pG8-FasL amplicon vectors. These vectors were relatively stable and exhibited minimal cytotoxicity in vivo. Intracranial implantation of pre-transduced glioma cells resulted in better survival outcome when compared with viral vectors inoculated one week post-implantation of tumor cells, indicating that therapeutic efficacy is dependent on the viral spread and mode of viral vectors administration. We further showed that pG8-FasL amplicon vectors are functional in the presence of commonly used treatment regimens for human brain cancer. In fact, the combined therapies of pG8-FasL and pG8-FADD in the presence of temozolomide significantly improved the survival of mice bearing intracranial high-grade gliomas.ConclusionTaken together, our results showed that the glioma-specific and cell cycle-dependent HSV-1 amplicon vector is potentially useful as an adjuvant therapy to complement the current gene therapy strategy for gliomas.
Highlights
Glioblastoma multiforme is the most malignant cancer of the brain and is notoriously difficult to treat due to the highly proliferative and infiltrative nature of the cells
The pG8-Fas ligand (FasL) amplicon viral vectors appeared to have lost its activities in HeLa cells, presumably due to the absence of specific cellular factors that are required for the glial fibrillary acidic protein (GFAP)-containing promoter to be functional (Figure 1C, right panel)
We have clearly demonstrated that the pG8-FasL amplicon viral vectors induced apoptosis in Glioblastoma multiforme (GBM)-derived cell lines and in proliferating primary human glioma cells
Summary
Glioblastoma multiforme is the most malignant cancer of the brain and is notoriously difficult to treat due to the highly proliferative and infiltrative nature of the cells. We explored the combination treatment of pre-established human glioma xenograft using multiple therapeutic genes whereby the gene expression is regulated by both cell-type and cell cycle-dependent transcriptional regulatory mechanism conferred by recombinant HSV-1 amplicon vectors. The failure of current therapeutic approaches to treat GBM is attributed to the high proliferative and infiltrative nature of these neoplasms [3]. We have previously constructed a Herpes Simplex Virus type 1 (HSV-1)-based amplicon vector in which the activation of the transgene expression is regulated by a G0/G1-specific transcriptional repressor protein termed cell cycle-dependent factor 1, CDF-1 [4]. As a proof-of-concept, we have chosen the Fas ligand (FasL) and the Fas-associated death domain (FADD/MORT1) as therapeutic genes because it is important that the effects derived from these genes should not mask the cell cycle-dependent function of the amplicon viral vectors
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