Viral Expression and Molecular Profiling in Liver Tissue versus Microdissected Hepatocytes in Hepatitis B Virus - Associated Hepatocellular Carcinoma

The molecular mechanisms whereby hepatitis B virus (HBV) induces hepatocellular carcinoma (HCC) remain elusive. We used genomic and molecular techniques to investigate host-virus interactions by mapping the entire liver of patients with HCC. We compared the gene signature of whole liver tissue (WLT) versus laser capture-microdissected (LCM) hepatocytes with intrahepatic expression of HBV. Gene expression profiling was performed on up to 17 WLT specimens obtained at various distances from the tumor center in individual livers of 11 patients with HCC and on selected LCM samples. HBV biomarkers were determined by real-time PCR and confocal immunofluorescence. Analysis of 5 areas of the liver showed a sharp change in gene expression between the immediate perilesional area and tumor periphery that correlated with a significant decrease in the intrahepatic expression of HBsAg. The tumor was characterized by a large preponderance of down-regulated genes, mostly involved in the metabolism of lipid and fatty acid, glucose, amino acids and drugs, with down-regulation of pathways involved in the activation of PXR/RXR and PPARa/RXRa nuclear receptors, comprising PGC1 and FOXO1, two key regulators of the hepatic metabolic functions and HBV transcription. These findings were confirmed by gene expression of microdissected hepatocytes. However, LCM of malignant hepatocytes also revealed up-regulation of unique genes associated with cancer and signaling pathways, including two novel HCC-associated cancer testis antigen (CTA) genes, NUF2 and TTK. HCC-associated with HBV is characterized by a metabolism switch-off and by a significant reduction in HBsAg. LCM proved to be a critical tool to validate gene signatures associated with HCC and to identify genes that may play a role in hepatocarcinogenesis opening new perspectives for the discovery of novel diagnostic markers and therapeutic targets. Samples were obtained at various distances from the tumor center in individual livers of 11 patients with HBV-associated HCC. Whole liver tissue samples were compared to LCM samples of malignant and non-malignant hepatocytes obtained from the same livers.