Our previous study has reported that mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) regulates the growth and survival of hepatocellular carcinoma (HCC) cells. This study was undertaken to explore the roles of MAP4K4 in the epithelial-mesenchymal transition (EMT) and metastasis in HCC. Effects of overexpression and knockdown of MAP4K4 on the migration, invasion, and EMT of HCC cells were examined. The in vivo role of MAP4K4 in lung metastasis of HCC was determined in nude mice. The relationship between MAP4K4 expression and EMT in human HCC specimens was determined by immunohistochemistry. MAP4K4 overexpression significantly enhanced the migration and invasion of MHCC-97L HCC cells, whereas MAP4K4 silencing hindered the migration and invasion of MHCC-97H HCC cells. MAP4K4-overexpressing cells undergo EMT, which was accompanied by downregulation of E-cadherin and upregulation of vimentin. In contrast, MAP4K4 silencing caused a reversion from a spindle morphology to cobblestone-like morphology and induction of E-cadherin and reduction of vimentin. Pretreatment with chemical inhibitors of JNK and NF-κB abolished MAP4K4-mediated migration, invasion, and regulation of EMT markers in MHCC-97L cells. Ectopic expression of MAP4K4 promoted and knockdown of MAP4K4 inhibited lung metastasis of HCC, which was associated with regulation of JNK and NF-κB signaling and EMT markers. High MAP4K4 immunoreactivity was inversely correlated with E-cadherin and was positively correlated with vimentin, phospho-JNK, and phospho-NF-κB in HCC specimens. Taken together, MAP4K4 promotes the EMT and invasiveness of HCC cells largely via activation of JNK and NF-κB signaling.
Keywords: Epithelial-mesenchymal transition; Hepatocellular carcinoma; Invasion; MAP4K4; Metastasis.