Endocrine Abstracts

The health burden associated with non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of the metabolic syndrome, continues to escalate. Not only is NAFLD associated with significant liver-specific and cardiovascular morbidity and mortality, but patients are at risk of the development of hepatocellular carcinoma (HCC); a malignancy where the incidence continues to rise and there are very limited therapeutic strategies.

Aldo-keto reductase 1C1 (AKR1C1) has a fundamental role in steroid hormone and drug metabolism. It has a variety of enzyme activities including converting progesterone to 20α-hydroxyprogesterone. AKR1C1 has been strongly associated with progression of cancers including breast and lung, as well as the development of chemotherapeutic drug resistance. AKR1C1 is most highly expressed in the liver, and yet its role to regulate metabolic and proliferative phenotype in human hepatocytes or hepatoma cell lines has not been explored. We have hypothesised that AKR1C1 activity contributes to enhanced hepatocellular proliferation through dysregulation of cell cycle regulators including the cyclin-dependent kinase (CDK) family that are crucial in driving G1/S transition. CDKs are also a target of the tumour suppressor, p53. We propose that AKR1C1 inhibition might represent a novel approach to the treatment of HCC. AKR1C1 was highly expressed in human liver, hepatocytes and hepatoma cell lines (HepG2 and Huh7). Functional activity in hepatoma cell lines was confirmed through the conversion of progesterone to pregnanediol-3-glucuronide, as measured by a commercially available ELISA. Cells were treated with the AKR1C1 inhibitor, 3-Bromo-5-phenylsalicylic acid (5-PBSA) (24 h, 100 µM), which successfully decreased enzyme activity (vehicle: 3.51 ± 1.08 vs 5-PBSA: 0.01 ± 0.01 ng/ml). In HepG2 and Huh7, AKR1C1 inhibition with 5-PBSA down-regulated the mRNA expression of multiple CDKs including CDK1, CDK2, CDK4and CDK6, as measured by real-time PCR. In addition, the cell division cycle 6 gene (CDC6), which encodes a protein crucial for DNA replication, was decreased following AKR1C1 inhibition. We have demonstrated the expression and functional activity of AKR1C1 in human hepatoma cell models. Inhibition with 5-PBSA had a profound impact to alter the expression of crucial cell cycle regulating genes, raising the possibility that AKR1C1 inhibition may represent an emerging strategy to treat HCC.