GSBS Dissertations and Theses

Approval Date

7-22-2016

Document Type

Doctoral Dissertation

Academic Program

Interdisciplinary Graduate Program

Department

Neurology

First Thesis Advisor

Miguel Sena-Esteves, Ph.D.

Keywords

Glioblastoma multiforme (GBM), gene therapy, AAV, adeno-associated virus, gene delivery, Interferon-beta

Subjects

Dissertations, UMMS; Glioblastoma; Genetic Therapy; Gene Transfer Techniques; Genetic Vectors; Interferon-beta; Dependovirus

Abstract

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor. The current standard-of-care treatment including surgery, radiation and temozolomide (TMZ) chemotherapy does not prolong the survival satisfactorily. Here we have tested the feasibility, efficacy and safety of a potential gene therapy approach using AAV as gene delivery vehicle for treatment of GBM.

Interferon-beta (IFNβ) is a cytokine molecule also having pleiotropic anticancerous properties. Previously it has been shown by our group that AAV mediated local (intracranial) gene delivery of human IFNβ (hIFNβ) could be an effective treatment for non-invasive human glioblastoma (U87) in orthotopic xenograft mouse model.But as one of the major challenges to treat GBM effectively in clinics is its highly invasive property, in the current study we first sought to test the efficacy of our therapeutic model in a highly invasive human GBM (GBM8) xenograft mouse model.

One major limitation of using the xenograft mouse model is that these mice are immune-compromised. Moreover, as IFNβ does not interact with cross-species receptors, the influence of immune systems on GBM remains largely untested. Therefore to test the therapeutic approach in an immune-competent mouse model, we next treated a syngeneic mouse GBM model (GL261) in an immune-competent mouse (C57B6) with the gene encoding the species-matched IFNβ (mIFNβ). We also tested if combination of this IFNβ gene therapy with the current standard chemotherapeutic drug (TMZ) is more effective than any one of the therapeutic modes alone. Finally, we tested the long term safety of the AAV-mIFNβ local gene therapy in healthy C57B6 mice.

Next, we hypothesized that global genetic engineering of brain cells expressing secretory therapeutic protein like hIFNβ could be more beneficial for treatment of invasive, migratory and distal multifocal GBM. We tested this hypothesis using systemic delivery of AAV9 vectors encoding hIFNβ gene for treatment of GBM8 tumor in nude mice.

Using in vivo bioluminescence imaging of tumor associated firefly luciferase activity, long term survival assay and histological analysis of the brains we have shown that local treatment of AAV-hIFNβ for highly invasive human GBM8 is therapeutically beneficial at an early growth phase of tumor. However, systemic delivery route treatment is far superior for treating multifocal distal GBM8 tumors. Nonetheless, for both delivery routes, treatment efficacy is significantly reduced when treated at a later growth phase of the tumor.

In syngeneic GL261 tumor model study, we show that local AAV-mIFNβ gene therapy alone or in combination with TMZ treatment can provide significant survival benefit over control or only TMZ treatment, respectively. However, the animals eventually succumb to the tumor. Safety study in the healthy animals shows significant body weight loss in some treatment groups, whereas one group shows long term survival without any weight loss or any noticeable changes in the external appearances. However, histological analysis indicates marked demyelinating neurotoxic effects upon long term exposures to mIFNβ over-expressions in brain. Overall, we conclude from this study that AAV-IFNβ gene therapy has great therapeutic potential for GBM treatment in future, but the therapeutic window is small and long term continuous expression could have severe deleterious effects on health.

DOI

10.13028/M2B59C

Rights and Permissions

Copyright is held by the author, with all rights reserved.

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