Introduction: Enhancer of zeste homolog 2 (EZH2) is implicated in hepatocellular carcinoma (HCC), but whether transforming growth factor-β (TGF-β)-metastasis associated 1 (MTA1)-SMAD7-SMAD3-SRY-Box Transcription Factor 4 (SOX4)-EZH2 signaling axis, in which EZH2 participates, is also involved in HCC remained unknown.
Methods: Data on EZH2 expression in liver hepatocellular carcinoma (LIHC) and its relation with prognosis of HCC patients were predicted and analyzed using online databases. Following transfection with or without TGF-β 1, HCC cell viability, migration and invasion were determined with MTT, Scratch and Transwell assays. Relative expressions of epithelial-to-mesenchymal transition (EMT)-related factors (N-Cadherin, Vimentin, and E-Cadherin) and TGF-β-MTA1-SMAD7-SMAD3-SOX4-EZH2 signaling axis factors (TGF-β, MTA1, SMAD7, phosphorylated-SMAD3, SOX4 and EZH2) were calculated via reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot.
Results: EZH2 was upregulated in HCC, which was related to poor prognosis. Silencing EZH2 suppressed EZH2 expression and HCC cell viability, migration, and invasion, and increased E-Cadherin expression yet decreased N-Cadherin and Vimentin expression, whereas EZH2 overexpression did conversely. Also, silencing EZH2 reversed the effects of TGF-β 1 on promoting viability, migration, and invasion, as well as N-Cadherin and Vimentin expressions, yet suppressing E-Cadherin expression in HCC cells. In addition, TGF-β 1 promoted TGF-β, MTA1, SOX4 and EZH2 expressions and p-SMAD3/SMAD3 ratio yet suppressed SMAD7, whereas silencing EZH2 solely reversed the effects of TGF-β 1 on EZH2 expression in HCC cells.
Conclusion: The present study provides a theoretical basis for TGF-β-MTA1-SMAD7-SMAD3-SOX4-EZH2 signaling cascade in viability, migration, invasion, and EMT of HCC cells. Inhibiting these signals may represent a therapeutic pathway for the treatment of metastatic HCC.
Keywords: hepatocellular carcinoma, enhancer of zeste homolog 2, transforming growth factor-β, metastasis, metastasis associated 1-SMAD7-SMAD3-SRY-box transcription factor 4 axis, MTA1-SMAD7-SMAD3-SOX4 axis