Alcohol-altered CEA processing: Role in liver metastases in colorectal cancer

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DESCRIPTION (provided by applicant): This application is in response to the Funding Opportunity Announcement (FOA), PA-12-234, from NIH and NIAAA entitled "Unconventional Roles of Ethanol Metabolizing Enzymes, Metabolites, and Cofactors in Health and Disease (R21)". The goal of this multiple-PI application is to examine how ethanol exposure can lead to altered processing and degradation of carcinoembryonic antigen (CEA), a glycoprotein secreted by tumor cells, and whose increase in the circulation has been linked to increased potential of colon cancer cells to form liver metastases. Colorectal cancer (CRC) accounts for 11% of all cancers in the United States, and the majority of deaths are attributed to liver metastases. There is a positive correlation between circulating CEA levels and alcohol consumption in liver metastasis in CRC patients, although the mechanism is not clear. What is known is that circulating CEA is removed primarily by the liver, where it binds to the CEA receptor (CEAR) on Kupffer cells (KCs). CEA binding results in activation of the KCs and production of several pro-inflammatory cytokines, including TNF-¿ and IL-6. Ultimately, CEA is desialylated within the KCs, released and subsequently endocytosed by the hepatocyte-specific asialoglycoprotein receptor (ASGPR). Both KCs and hepatocytes are known to be significantly impacted by alcohol, and we hypothesize that those alcohol-related effects to both KCs and hepatocytes will contribute to altered CEA processing, resulting in changes to the liver microenvironment and enhancement in the metastatic potential of CRC cells. We also predict that CEA- mediated production of KC-derived cytokines will affect adhesion molecule expression on the hepatic sinusoidal endothelium, resulting in changes in the liver microenvironment, thus supporting development of liver metastases in the alcoholic. To examine this hypothesis, we have proposed two specific aims; in Aim 1 we will focus on the direct effect of alcohol administration on CEA processing in KCs isolated from control and ethanol-fed rats, and in Aim 2 we will characterize the indirect effect of alcohol administration on CEA processing by examining the role of hepatocellular degradation. The two principal investigators involved in this application have complementary strengths which are essential for the success of the project. Dr. Casey is an expert in alcoholic-induced liver damage, and has extensive experience with the effect of alcohol on liver cells in a rat model. Dr. Thomas is an expert in CEA and CEA receptor biology, who has over 40 years of experience and extensive publications in this field. Together, we will utilize a variety of state-of-the art techniques to evaluate the unique processing of CEA, including co-culture systems of liver parenchymal and non-parenchymal cells, RNA interference approaches and radiolabeled ligand binding assays. We anticipate that the successful completion of this project will provide key information that could lead to therapeutic strategies aimed at reducing or eliminating liver metastases and increase our understanding of how alcoholic liver injury exacerbates the effects of CEA.