p28(GANK) Overexpression Accelerates Hepatocellular Carcinoma Invasiveness and Metastasis via Phosphoinositol 3-Kinase/AKT/Hypoxia-Inducible Factor-1 alpha Pathways

The overall survival of patients with hepatocellular carcinoma (HCC) remains poor, and the molecular mechanisms underlying HCC progression and aggressiveness are unclear. Here, we report that increased expression of p28(GANK) (Gankyrin, PSMD10, or p28) in human HCC predicts poor survival and disease recurrence after surgery. Patients with HCC who have large tumors, with vascular invasion and intrahepatic or distant metastasis, expressed high levels of p28(GANK). Invasive tumors overexpressing p28(GANK) were featured by active epithelial-mesenchymal transition (EMT), and exhibited increased angiogenesis associated with vascular endothelial growth factor overexpression, whereas silencing p28(GANK) expression attenuated EMT and motility/invasion of tumor cells. The p28(GANK) activates phosphoinositide 3-kinase (PI3K)-V-akt Murine Thymoma Viral Oncogene Homolog (AKT)-hypoxia-inducible factor 1 alpha (HIF-1 alpha) signaling to promote TWIST1, vascular endothelial growth factor, and metalloproteinase 2 expression. Suppression of the PI3K-AKT-HIF-1a pathway interfered with p28(GANK)-mediated EMT and invasion. Consistently, we detected a significant correlation between p28(GANK) expression and p-AKT levels in a cohort of HCC biopsies, and the combination of these two parameters is a more powerful predictor of poor prognosis. Conclusion: These results present novel mechanistic insight into a critical role of p28(GANK) in HCC progression and metastasis. (HEPATOLOGY 2011;53:181-192)