Abstract
Mammalian sterile-20-like kinase 4 (MST4) has been implicated in cell proliferation and differentiation. In a previous study, we found MST4 to be an important candidate gene for metastatic hepatocellular carcinoma (HCC); however, the molecular mechanism of the promoting role of MST4 in HCC metastasis is poorly understood. In this study, we show that high expression of MST4 was detected in highly invasive HCC cells and in human HCC specimens with vascular invasion. A high level of MST4, associated with large tumor size, microvascular invasion, presence of intrahepatic metastasis, and advanced TNM classification of malignant tumors stage, was an independent prognostic factor for overall survival (P=0.004) and time to recurrence (P=0.001) after hepatectomy. Knockdown of MST4 expression in HCC cells inhibited cell proliferation, colony formation, and invasion, whereas upregulation of MST4 significantly promoted these processes by promoting epithelial-mesenchymal transition (EMT), dependent on the activation of extracellular signal-regulated protein kinase (ERK) signaling pathways. Furthermore, the combination of MST4 and phosphorylated ERK was proven to have more power to predict the outcomes of HCC patients. This study presents clinical evidence for predicting the value of MST4 in HCC overall survival and recurrence and describes the key role of MST4 in facilitating the EMT process via regulating the activation of ERK, indicating its potential role as a target for postoperative adjuvant therapy for HCC.