Overexpression of epidermal growth factor (EGF) in the liver induces transformation to hepatocellular carcinoma (HCC) in animal models. A single nucleotide polymorphism (A to G transition at position 61) has been identified in the EGF gene. We have demonstrated increased mRNA stability of the G allele both in hepatoma cell lines and primary human hepatocytes which may serve as a mechanism by which individuals with the G/G genotype have increased serum and liver tissue levels. Our analysis of the distribution of allelic frequencies in cirrhosis populations from both Massachusetts and France revealed that the G/G genotype was significantly associated with risk of HCC relative to the A/A genotype. Currently, the source of excess EGF is unknown. The majority of HCCs develop in the setting of cirrhosis. Therefore, the goal of Specific Aim 1 is to investigate the effects of cirrhosis on EGF expression in serum and the various liver cell populations as monitoring of EGF levels could be used to identify cirrhosis patients at high-risk for HCC. HCC is increasing in incidence both in the United States and worldwide. Given the lack of successful treatment options for HCC, chemoprevention in high-risk patients has been proposed as an alternative strategy. Exceedingly little is known about the molecular pathways leading to hepatocellular transformation. Therefore, the goal of Specific Aim 2 is to examine the signaling pathways initiated during EGF-induced transformation as a means to identify potential therapeutic targets. Small molecule EGF receptor (EGFR) tyrosine kinase inhibitors have proven effective as chemopreventive agents in a rat model of HCC. The goal of Specific Aim 3 is to identify resistance mechanisms in the residual tumors in order to design more effective chemoprevention strategies. The broad long-term objective of this proposal is to develop chemopreventive therapies that can be used to lower EGF levels and/or inhibit EGF-induced hepatocellular transformation. The data obtained from these experiments have broad implications as overexpression of the EGFR is a common event in neoplastic transformation, and we hypothesize that targeting of the EGF pathway may be a novel strategy for chemoprevention.
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