RESISTANCE TO VESICULAR STOMATITIS VIRUS IS INTRINSIC TO PC3 PROSTATE CANCER CELLS AND CAUSES INHIBITION OF EARLY STEPS OF THE VIRUS REPLICATION CYCLE

The goal of the experiments presented in this thesis was to determine the mechanism(s) of resistance of prostate cancer cells to the oncolytic activity of vesicular stomatitis virus (VSV). In Chapter 1 I analyzed the timing of the different steps of the virus replication cycle in PC3 prostate cancer cells (VSV-resistant cells) to LNCaP prostate cancer cells (VSV-sensitive cells). My experiments revealed that several early steps of the viral replication cycle are delayed in PC3 cells, including virus penetration and primary transcription. One major difference between these two cell types is that PC3 cells constitutively overexpress antiviral mRNAs and proteins. Combined with the delays at several steps of the viral life cycle, these observations led to the two hypotheses tested in Chapter 2, which address whether PC3 cell resistance is intrinsic to these cells or whether it is induced as a result of an antiviral response. The first hypothesis tested in Chapter 2 was that PC3 cells rapidly produce an antiviral response, and this induced response makes them resistant to VSV. This hypothesis was tested using an M protein mutant virus that is defective in its ability to suppress host antiviral responses, and by silencing the expression of STAT1, a major transcription factor responsible for antiviral gene expression in response to interferons. The alternative hypothesis was that PC3 cells have intrinsic resistance to VSV, due to their constitutive expression of antiviral genes or other gene products that confer resistance to virus replication. The results from Chapter 2 revealed that although VSV infection does induce an antiviral response in PC3 cells that provides some protection from virus infection, the induced response is not necessary for the resistance of these cells and cannot account for the observed delays in the viral replication cycle. Finally, in Chapter 3 I address the question of whether overexpression of the antiapoptotic protein Bcl-xL plays a role in resistance of prostate cancer cells to VSV. By overexpressing Bcl-xL in VSV-sensitive LNCaP cells and silencing Bcl-xL expression in VSV-resistant PC3 cells, I was able to demonstrate that the level of Bcl-xL expression is important for resistance to VSV. Reducing Bcl-xL in PC3 cells greatly increased their sensitivity to VSV-induced apoptosis. However, this resistance to apoptosis could not account for the overall resistance of PC3 cells to VSV, and instead was a distinct aspect of PC3 cell intrinsic resistance.

Grantor dc:publisher

Wake Forest University

Year dc:date.issued

2009

Author dc:creator

• Cody, Brooke Lea

• Medicine

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10339/14654

OAI identifier oai:identifier

oai:wakespace.lib.wfu.edu:10339/14654