Abstract 2467: Role of adrenomedullin in woodchuck hepatocarcinogenesis
Authors: Ochoa Laura , Coca Valle , Toshkov Ilia A. , Liu Katherine H. , Menne Stephan , Martínez Alfredo 
Published: February 2011

The aim of this study is to investigate the role of adrenomedullin (AM) during the development of hepatocellular carcinoma (HCC). AM is a growth factor for tumor cells and induces angiogenesis. Woodchucks chronically infected with the woodchuck hepatitis virus (WHV) represent the best animal model for studying hepadnavirus-induced HCC. We sought to determine whether AM signaling is functionally active in woodchuck HCC and how it correlates with tumor development and disease progression. Furthemore, increased expression and activity of matrix metalloproteinases (MMPs) in HCC patients is associated with advanced tumor stage, metastasis and poor survival. MMPs are further known to regulate AM cleavage. Therefore, we also sought to determine the role of MMPs in HCC development using the preclinical woodchuck model.

For identifying a partial sequence of woodchuck AM (wAM), primers specific for human AM were utilized in PCR amplification. The resulting PCR products were sequenced and analyzed. The cellular localization of wAM was determined by immunohistochemical staining. AM and AKT expression levels were also compared by western blot between liver tissues from WHV-uninfected woodchucks, non-tumorous and tumorous liver tissues from chronic carrier woodchucks at different stages of HCC. Gelatin zymographic analysis was performed on woodchuck serum and liver samples in order to quantify the activity of MMPs following densitometry.

The wAM consensus sequence revealed a 98% homology to human AM at the amino acid level. Compared to non-tumorous liver tissue, wAM protein expression was increased in adjacent tumorous tissues from the same chronic carrier woodchuck with HCC. wAM expression was detected mainly in hepatocytes and kupffer cells located within areas of portal hepatitis. In addition, the staining intensity for wAM was higher in tumorous hepatocytes than in non-tumorous or WHV-unifected hepatocytes. pAKT was also upregulated in tumoral liver tissues. Activity of MMP-9 was significantly increased in tumorous liver tissues as determined by zymography.

Hepatic wAM gene expression in chronic carrier woodchucks is markedly upregulated during progression from normal to cancerous liver, and increases in wAM expression correlate with the degree of tumor malignancy in these animals. This increased wAM expression seems to be mediated through the activation of the PI3K (phosphoinositide 3-kinase)/Akt pathway. Furthermore, increased MMP-9 activity could be a factor in HCC invasiveness. Our results suggest that wAM-mediated neovascularization plays an important role in the hepatocarcinogenesis of WHV-infected woodchucks. Future studies will investigate if the blockage of the wAM signaling pathway in chronic carrier woodchucks alters hepadnavirus-induced liver carcinogenesis as a preclinical test for treatment of HCC in humans.

This study was funded by a grant from the Spanish Ministry of Science and Innovation: SAF2009-13240-C02-01

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2467.