Date of Award

January 2013

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

W. Mark Saltzman

Subject Area(s)

Cellular biology, Biomedical engineering, Molecular biology

Abstract

Glioblastoma multiforme (GBM), the most common primary brain malignancy, carries a grim prognosis; survival statistics have scarcely improved in decades. Even with the development of temozolomide, the current front-line chemotherapeutic agent for GBM, improvement in long-term survival has been minimal, with recurrence virtually assured. One explanation for the persistence of this disease is the presence of a stem-like cell population within GBM (glioblastoma stem cells, or GSCs). These cells are capable of self-renewal, tumor initiation, and are resistant to chemotherapy. We hypothesized that derangement in the expression of genes critical for the maintenance of GSCs could eliminate these cells outright, or induce sufficient cell differentiation to sensitize them to existing chemotherapeutic agents. To this end we performed a genome-wide small interfering RNA (siRNA) screen in search of genes that, when reduced in expression, cause GSC cell death or induce differentiation as measured by changes in nestin expression or cell morphology. Our screening yielded a number of candidate siRNAs: their efficacy in reducing cell viability was demonstrated across a number of genetically distinct GSC cell lines. We further identified two siRNAs, targeting ubiquitin C (UBC) and disheveled 2 (DVL2), respectively, that significantly sensitize GSCs to the effects of temozolomide (p<0.05). A similar but not significant effect was also observed in combination treatment with siRNA and either paclitaxel or doxorubicin. We conclude from these observations that siRNA-mediated gene knockdown presents a promising avenue in the development of novel treatments for GBM by taking into account the unique biologic attributes of the therapeutically problematic GSC population.

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