This renewal application is based on a conceptual and technological breakthrough made during the current project period - identification and isolation of pre-neoplastic cells that serve as precursors for hepatocellular carcinoma (HCC) in mice. HCC is one of the most aggressive and difficult to treat cancers, with a current 5 year survival rate of 8%, yet HCC develops over the course of 20-40 years in the context of chronic liver inflammation (hepatitis) and damage. HCC development is preceded by appearance of foci of altered hepatocytes (FAH), which have been suspected (but never proven) to represent pre-neoplastic lesions. We succeeded in isolating HCC progenitor cells (HPC) from two different mouse HCC models and obtained evidence suggesting that HPC reside within FAH in mice treated with a chemical carcinogen that targets hepatocytes. Curiously, HPC appear to be related, based on their gene expression profile, to oval cells, a bipotential progenitor cell involved in repair of certain liver injuries in mice and men. However, it is not clear whether HPC arise from oval cells or from differentiated hepatocytes which are the target for the carcinogen. Understanding the mechanisms that control formation of HPC and their progression to full blown HCC will enable the development of preventive and therapeutic strategies for HCC eradication at an early stage, before this malignancy becomes refractory to all known therapies. In addition to cell intrinsic factors, progression of HPC to HCC is subject to micro environmental control. Correspondingly, we will investigate the mechanisms responsible for initiation and maintenance of activated STAT3, a critical oncogenic transcription factor, in HPC. These studies will explain how STAT3 activation is maintained within HPC and HCCs, but not in the adjacent normal liver, even though the normal tissue is exposed to STAT3-activating cytokines. We will investigate the contribution of these mechanisms to HPC to HCC progression by their genetic manipulation within isolated HPC. We will also study the role of the cell surface protein and stem cell marker CD44 in HPC formation and HPC to HCC progression, as our preliminary results indicate that HPC express CD44 and that CD44 is essential for FAH formation and HCC development. We will study the mechanisms responsible for CD44 upregulation in HPC and for production of the alternatively spliced CD44v6 isoform that interacts with c-Met and potentiates its signaling activity. Another marker expressed by HPC is the transcription factor Sox9, which is also expressed in oval cells. We will investigate the mechanisms responsible for Sox9 expression in HPC, focusing on the role of the Notch pathway and will exploit Sox9 in lineage tracing experiments that will determine the origin of HPC.

Public Health Relevance

We will investigate the mechanisms responsible for generation and maintenance of liver cancer progenitor cells and their progression into malignant tumors. These studies will lead to development of therapeutic and preventive strategies that target liver cancer progenitors instead of malignant tumors that are refractory to conventional therapy.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA118165-06
Application #
8297428
Study Section
Molecular Oncogenesis Study Section (MONC)
Program Officer
Watson, Joanna M
Project Start
2005-12-01
Project End
2017-03-31
Budget Start
2012-04-01
Budget End
2013-03-31
Support Year
6
Fiscal Year
2012
Total Cost
$446,341
Indirect Cost
$158,147
Name
University of California San Diego
Department
Pharmacology
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Dhar, Debanjan; Antonucci, Laura; Nakagawa, Hayato et al. (2018) Liver Cancer Initiation Requires p53 Inhibition by CD44-Enhanced Growth Factor Signaling. Cancer Cell 33:1061-1077.e6
Febbraio, Mark A; Reibe, Saskia; Shalapour, Shabnam et al. (2018) Preclinical Models for Studying NASH-Driven HCC: How Useful Are They? Cell Metab :
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Sanchez-Lopez, E; Flashner-Abramson, E; Shalapour, S et al. (2016) Targeting colorectal cancer via its microenvironment by inhibiting IGF-1 receptor-insulin receptor substrate and STAT3 signaling. Oncogene 35:2634-44
Moscat, Jorge; Karin, Michael; Diaz-Meco, Maria T (2016) p62 in Cancer: Signaling Adaptor Beyond Autophagy. Cell 167:606-609

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