Metastasis contributes to the poor prognosis of hepatocellular carcinoma （HCC）. However, the mechanism through which a primary HCC cell develops into a metastatic phenotype is not well understood. The purpose of this study was to examine the correlation between metadherin （MTDH）/ astrocyte elevated gene-1 （AEG-1） expression in HCC cell lines of different metastatic potentials and such metastatic phenotypes as orientation chemotaxis and adhesion. MTDH/AEG-1 expression was detected by RT-PCR and western blotting in HCC cell lines （HepG2, Huh7, Sk-HEP-1, MHCC-97H）. Distribution of MTDH/AEG-1 was observed by immunofluorescence staining and confocal laser scanning microscopy. The abilities of orientation chemotaxis and adhesion and the index of interaction between HCC cell lines and microvascular endothelial cell lines （MVECs, including HUVECs and HPMECs） were measured by chemotaxis assay and adhesion assay, respectively. The results showed that MTDH/AEG-1 protein expression was significantly higher in high metastatic potential cancer cell lines （Sk-HEP-1, MHCC-97H ） than in low metastatic potential cell lines （HepG2, Huh7） （P〈0.05）. The MTDH/AEG-1 protein was localized in the perinuclear region of HCC cells. Furthermore, the abilities of orientation chemotaxis and adhesion of HCC cells to HPMECs were increased as compared with those of HCC cells to HUVECs （P〈0.05）. The abilities of orientation chemotaxis and adhesion were much stronger in Sk-HEP-1 and MHCC-97H cells with MTDH/AEG-1 highly expressed than in HepG2 and Huh7 cells with MTDH/AEG-1 lowly expressed （P〈0.05）. These results suggested that the expression of MTDH/AEG-1 gene in HCC cell lines of different metastatic potentials was closely positively related to the abilities of orientation chemotaxis and adhesion of HCC cells. It was deduced that MTDH/AEG-1 might play a pivotal role in the lung-specific metastasis of HCC, which may be medi-ated through orientation chemotaxis and adhesion abilities of HCC cells. MTDH/A
