Protein profile in HBx transfected cells: a comparative iTRAQ-coupled 2D LC-MS/MS analysis.

The x protein of HBV (HBx) has been involved in the development of hepatocellular carcinoma (HCC), with a possible link to individual genotypes. Nevertheless, the underlying mechanism remains obscure. In this study, we aim to identify the HBx-induced protein profile in HepG2 cells by LC-MS/MS proteomics analysis. Our results indicated that proteins were differentially expressed in HepG2 cells transfected by HBx of various genotypes. Proteins associated with cytoskeleton were found to be either up-regulated (MACF1, HMGB1, Annexin A2) or down-regulated (Lamin A/C). These may in turn result in the decrease of focal adhesion and increase of cell migration in response to HBx. Levels of other cellular proteins with reported impact on the function of extracellular matrix (ECM) proteins and cell migration, including Ca(2+)-binding proteins (S100A11, S100A6, and S100A4) and proteasome protein (PSMA3), were affected by HBx. The differential protein profile identified in this study was also supported by our functional assay which indicated that cell migration was enhanced by HBx. Our preliminary study provided a new platform to establish a comprehensive cellular protein profile by LC-MS/MS proteomics analysis. Further downstream functional assays, including our reported cell migration assay, should provide new insights in the association between HCC and HBx.