Date on Master's Thesis/Doctoral Dissertation

11-2013

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Pharmacology and Toxicology

Degree Program

Pharmacology and Toxicology, PhD

Committee Chair

McMasters, Kelly

Committee Co-Chair (if applicable)

Zhou, Heshan

Committee Member

Zhou, Heshan

Committee Member

Nerland, Donald

Committee Member

Powell, David

Committee Member

Zacharias, Wolfgang

Abstract

Virus-mediated oncolysis has been considered as a new and promising cancer therapeutic approach. Although adenoviruses (Ads) with deletion of E1b55K preferentially replicate in cancer cells and have been used in numerous cancer treatments, the selective replication mechanism of this kind of virus still remains controversial. The lack of a well-established studies focusing on possible mechanisms enabling tumor selectivity of oncolytic Ads has hindered the further development of virotherapies and limits their clinical applications. Therefore, uncovering the molecular basis behind the tumor-killing phenomena will fill critical gaps in our understanding of the oncolytic adenovirology. Previously our laboratory has demonstrated that Ad E1B55K protein is involved in cyclin E induction that is required for efficient virus replication. However, functional E1B55K expression is not required for oncolytic Ad replication in cancer cells, many of which have deregulated cyclin E overexpression. In this dissertation we advanced the previous findings to further develop the mechanism model of selective oncolytic replication of E1b-deleted Ads, and then applied these insights to design a novel tumor-specific oncolytic Ad vector. We demonstrated that Ad-induced cyclin E subsequently activates CDK2 that targets the transcriptional suppressor pRb to generate a cellular environment for productive viral replication. Based on this understanding, a novel tumor-specific oncolytic vector, Ad-cycE, was developed in which the cyclin E promoter was used to control a critical regulatory viral E1a gene. As cyclin E is greatly induced in cancer cells after Ad transduction, Ad-cycE shows significant oncolytic efficacy in vitro and strongly repressed tumor growth in vivo. Additional work has been completed exploring the impact of using a combination treatment of Ad-cycE and rapamycin which induces autophagy; the results indicated a synergistic antitumor effect that was statistically significant. This work has advanced our knowledge of the cancer selectivity of E1b-deleted Ads, and will lead to further progress in the field of oncolytic virotherapy.

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