Defense Date

2019

Document Type

Thesis

Degree Name

Master of Science

First Advisor

Devanand Sarkar

Second Advisor

Xiang-Yang Wang

Third Advisor

Kristoffer Valerie

Abstract

Liver cancer is the fourth leading cause of cancer-associated deaths globally, and among primary liver cancers, hepatocellular carcinoma (HCC) encompasses 75-85% of all cases. HCC is a highly lethal disease due to limited treatment options – only a small subset of patients qualify for surgical resection or transplantation; the remaining patients often display resistance to radiation therapy or chemotherapy. Overexpression of the oncogene astrocyte elevated gene-1 (AEG-1) is associated with poorer survival and increased tumor recurrence in HCC, and numerous studies show its role in initiation of hepatocarcinogenesis. A prior study also demonstrated AEG-1 expression inhibits senescence by diminishing the ATM/Chk1/Chk2/p53/p21 DNA damage response (DDR) pathway. The aim of this study is to understand if AEG-1 expression promotes radioresistance in HCC. A CRISPR/Cas9 plasmid system was used to delete AEG-1 in the QGY-7703, HuH7 and DihXY cell lines, which model HCC. The cell lines were then treated with ionizing radiation (IR). We find that knockout of AEG-1 in these cell lines induces sensitivity to IR at 2.5 Gy. In response to radiation, AEG-1 wildtype cells more profoundly upregulate ATR, Chk1, and Chk2 signaling; and also more rapidly induce γH2AX, ATM, and BRCA1 signaling, which sense dsDNA breaks to initiate homologous recombination repair. We conclude that AEG-1 expression protects HCC cells from IR through two mechanisms: 1) rapidly initiating the DNA damage response; and 2) increasing replication fork stabilization. These findings indicate AEG-1 can be a therapeutic target in combination with radiation treatment to improve outcomes for HCC patients who demonstrate radioresistance.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-9-2019

Available for download on Friday, May 08, 2020

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