Hepatocellular carcinoma, the major manifestation of liver cancer is a major health concern. Currently, this disease is the 3rd leading cause of cancer deaths worldwide with over 500,000 deaths each year. The high incidence of hepatocellular carcinoma development is attributed to environmental insult or viral infections that can induce chronic liver damage and tumor development. One of the key genetic lesions found in liver cancer is inactivation of the retinoblastoma tumor suppressor (RB) pathway. This pathway is disrupted in most liver tumors;however, the role of RB loss in tumor etiology and progression remains largely undefined. Classically, RB is believed to inhibit cell cycle progression and serves as a critical deterrent to hyperplastic proliferation. To determine the mechanism(s) by which RB prevents tumor formation in the liver, we developed a mouse model of liver specific RB deletion. While RB loss causes transient alterations in cell cycle control, no hyperplasia was observed. Rather, RB-deficient hepatocytes undergo aberrant rounds of DNA replication leading to alterations in DNA ploidy suggesting a role for RB in the maintenance of genome integrity. The effects of RB loss are exacerbated by challenge with hepatocarcinogens, wherein the RB loss synergized with carcinogenic exposure to promote genome instability. These effects on genome stability are associated with a striking predisposition of RB-deficient livers to tumorigenesis. Combined, these data reveal novel mechanisms of RB function, and suggest that RB action in this tissue is distinct from its ability to prevent unchecked cellular proliferation. Rather, our data support the hypothesis that RB loss cooperates with hepatic carcinogens to induce genomic instability and promote liver tumorigenesis. We challenge this hypothesis and the role of RB in liver cancer by: determining the mechanisms through which RB loss compromises cell cycle control to alter genome stability in the liver (Aim 1);delineating the impact of RB loss on genome stability and hepatocarcinogenesis under specific pathologic conditions (Aim 2);and defining the action of temporal gene/environment and gene/gene interactions on liver tumorigenesis (Aim 3).
Liver cancer is the 3rd leading cause of cancer deaths worldwide with in excess of 500,000 cases. A key event occurring in most liver cancers is loss of the retinoblastoma tumor suppressor pathway. In this proposal we will dissect how disruption of this pathway contributes to liver cancer that will support long-term efforts to intervene more-effectively in preventing and treating this disease.
|Hutcheson, Jack; Bourgo, Ryan J; Balaji, Uthra et al. (2014) Retinoblastoma protein potentiates the innate immune response in hepatocytes: significance for hepatocellular carcinoma. Hepatology 60:1231-40|
|Reed, Christopher; Hutcheson, Jack; Mayhew, Christopher N et al. (2014) RB tumor suppressive function in response to xenobiotic hepatocarcinogens. Am J Pathol 184:1853-9|
|DelBove, Jessica; Rosson, Gary; Strobeck, Matthew et al. (2011) Identification of a core member of the SWI/SNF complex, BAF155/SMARCC1, as a human tumor suppressor gene. Epigenetics 6:1444-53|
|McClendon, A Kathleen; Dean, Jeffry L; Ertel, Adam et al. (2011) RB and p53 cooperate to prevent liver tumorigenesis in response to tissue damage. Gastroenterology 141:1439-50|
|Bourgo, Ryan J; Thangavel, Chellappagounder; Ertel, Adam et al. (2011) RB restricts DNA damage-initiated tumorigenesis through an LXCXE-dependent mechanism of transcriptional control. Mol Cell 43:663-72|
|Rivadeneira, Dayana B; Mayhew, Christopher N; Thangavel, Chellappagounder et al. (2010) Proliferative suppression by CDK4/6 inhibition: complex function of the retinoblastoma pathway in liver tissue and hepatoma cells. Gastroenterology 138:1920-30|
|Reed, C A; Mayhew, C N; McClendon, A K et al. (2009) RB has a critical role in mediating the in vivo checkpoint response, mitigating secondary DNA damage and suppressing liver tumorigenesis initiated by aflatoxin B1. Oncogene 28:4434-43|