The long-term goal is to develop novel drug therapy for liver cancer, the 2rd leading cause of cancer death worldwide. Phosphatase and tensin homolog (PTEN), a key tumor suppressor and metabolic regulator, is frequently mutated/silenced in human liver cancers. Mice with liver-specific knockout (LKO) of Pten develop progressive steatohepatitis, cirrhosis, and liver carcinoma. The molecular mechanisms and histological feature in Pten-null mice closely resemble the pathogenesis of non-alcoholic steatohepatitis (NASH) and liver cancer in humans. Glucocorticoid receptor (GR) critically regulates liver pathophysiology. Literature shows that GR signaling is largely impaired in human hepatocellular carcinoma (HCC), and our preliminary data showed that hepatic GR-target genes were markedly down-regulated in liver tumors developed in Pten LKO mice. However, the roles of hepatic GR in the pathogenesis and treatment of PTEN-deficiency-induced NASH and liver cancer remain unclear; such knowledge gaps will be bridged by this study. Literature reports and our preliminary data strongly suggest that activation of GR can not only treat liver cancer, but also protect against liver injury and liver fibrosis. However, activation of GR in extrahepatic tissues can cause many side effects that negate the benefits of glucocorticoid (GC) therapy in liver cancer. Bile acid (BA)-drug conjugates have been successfully developed for liver-specific drug targeting via the liver-specific BA transporter Na+- taurocholate cotransporting polypeptide (NTCP). We have successfully synthesized two first-in-class cholic acid (CA) conjugates of dexamethasone (DEX-CA) and verified their NTCP-dependent transport and cellular activity. The objective of this R03 proposal is to develop DEX-CAs as new prodrug candidates for liver cancer, and uncover how liver-specific deficiency and activation of GR regulate hepatic gene expression and the progression from NASH to liver cancer. The central hypothesis is that GR in hepatocytes is essential to protect against NASH and liver cancer. By decreasing the adverse effects of GCs in extrahepatic tissues and exerting cytoprotection, anti-inflammation, anti-fibrotic, and anti-cancer effects in the liver, NTCP-mediated liver-specific GR activators will be a highly novel therapy for NASH-induced liver cancer.
Aim 1 will delineate how gene-dosage-dependent liver-specific deficiency of GR in mice affects the progression from steatosis to liver cancer induced by Pten deficiency.
Aim 2 will delineate how liver-specific activation of GR by DEX-CAs affects NASH and liver cancer in Pten LKO mice. This R03 proposal is highly innovative because of its conceptual advances and up-to-date approaches. This study will develop novel DEX-CA conjugates as new prodrug candidates and the first pharmacological tool for liver-specific activation of GR. It will uncover novel roles of liver-specific gene-dosage-dependent GR deficiency and activation of GR in the pathogenesis and treatment of PTEN-deficiency-induced NASH and liver cancer. This will help develop innovative therapy of NASH and liver cancer via NTCP-mediated delivery of DEX-CA conjugates for liver-specific activation of GR.
Relevance to Public Health: The United States has increasing incidence of liver cancer, a deadly disease that lacks effective drug treatment. The proposed studies are of importance in the under-investigated area of the pathogenesis and drug treatment of liver cancer induced by the deficiency of a key tumor-suppressor. Thus, the findings are expected to enhance our understanding of liver cancer, and will help develop highly novel drug candidates to prevent and treat liver cancer.
