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Dissertation
Investigation of mechanisms of hepatitis B virus (HBV) carcinogenesis in HBV transfected HEPG2 cells
Doctor of Philosophy (Ph.D.), Medical College of Pennsylvania and Hahnemann University
Feb 1999
DOI:
https://doi.org/10.17918/00008688
Abstract
Hepatitis B virus (HBV) is a major etiological factor associated with hepatocellular carcinoma (HCC) but its exact role in the transformation process remains unclear. Among several possible mechanisms it has been proposed that HBV functions directly or indirectly in HCC by promoting instability and chromosomal aberrations in hepatocytes. Recent reports suggest that the HBV DNA spanning the open reading frame that encodes the HBX protein interacts with several DNA repair factors and compromises the cell's ability to repair damaged DNA. The work summarized in this thesis was designed to explore the overall question whether or not the introduction and replication of HBV affects the genetic integrity of the host genome as measured by the identification of genetic alterations and HBV status in the host cell. First, we used three hepatoblastoma cell lines of the same genetic origin: the parental HepG2 cells, free from HBV virus, and its two HBV transfected variants-HepG2T14.1, with integrated non-replicating virus, and HepG2215, with integrated and actively replicating virus. We monitored genetic alterations in these cells in conjunction with HBV profile in vitro and in vivo to address the effect of HBV and its replication status on the integrity of the host genome. Our work demonstrate additional genetic changes at the chromosome and molecular levels in both HBV transfected cell lines that are not found in the original HepG2 cell line. Both HBV transfected variants developed tumors in nude mice within three weeks in contrast to parental HepG2 cells that did not form tumors in nude mice at that time period. A new HBV integration site was identified in HepG2215 cells replicating HBV while HepG2T14.1 cells maintained one stable HBV integration site. Further genetic alterations as well as clonal selection of particular changes were detected in both HBV transfected tumor derived cell lines. These data provide evidence that genomic integrity was affected in both HBV transfected variants and suggest that HBV and viral replication in the host cell is associated with enhanced genetic instability. We next investigated HepG2 transfectants with stable expression of the HBX gene to determine if expression of HBX gene is associated with genetic alterations in the host genome. We document HepG2 cells expressing the HBX gene have enhanced chromosome damage consisting of an increased number of chromosome rearrangements and micronuclei formation compared to their vector controls. This data provides cytogenetic evidence that genomic integrity was affected in cells expressing the HBX gene and implicate HBX in the process that leads to genetic alterations. Together, these results support the hypothesis that HBV, in particular HBY, may indirectly play a role in cellular transformation by interfering with normal cellular processes responsible for maintaining genomic stability, promoting the accumulation of genetic alterations and increasing the probability of neoplasia.
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Details
- Title
- Investigation of mechanisms of hepatitis B virus (HBV) carcinogenesis in HBV transfected HEPG2 cells
- Creators
- Kristin Wallace Livezey
- Contributors
- D. Simon (Advisor) - Drexel University, Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Awarding Institution
- Medical College of Pennsylvania and Hahnemann University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Medical College of Pennsylvania and Hahnemann University; Philadelphia, Pennsylvania
- Number of pages
- x, 120 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Other Identifier
- 991021888827404721