Hepatic stellate cell (HSC) activation plays an important role in the pathogenesis of liver fibrosis, and epithelial-mesenchymal transition (EMT) is suggested to potentially promote HSC activation. Superoxide dismutase 3 (SOD3) is an extracellular antioxidant defense against oxidative damage. Here, we found downregulation of SOD3 in a mouse model of liver fibrosis induced by carbon tetrachloride (CCl 4). SOD3 deficiency induced spontaneous liver injury and fibrosis with increased collagen deposition, and further aggravated CCl 4-induced liver injury in mice. Depletion of SOD3 enhanced HSC activation marked by increased α-smooth muscle actin and subsequent collagen synthesis primarily collagen type I in vivo, and promoted transforming growth factor-β1 (TGF-β1)-induced HSC activation in vitro. SOD3 deficiency accelerated EMT process in the liver and TGF-β1-induced EMT of AML12 hepatocytes, as evidenced by loss of E-cadherin and gain of N-cadherin and vimentin. Notably, SOD3 expression and its profibrogenic effect were positively associated with sirtuin 1 (SIRT1) expression. SOD3 deficiency inhibited adenosine monophosphate-activated protein kinase (AMPK) signaling to downregulate SIRT1 expression and thus involving in liver fibrosis. Enforced expression of SIRT1 inhibited SOD3 deficiency-induced HSC activation and EMT, whereas depletion of SIRT1 counteracted the inhibitory effect of SOD3 in vitro. These findings demonstrate that SOD3 deficiency contributes to liver fibrogenesis by promoting HSC activation and EMT process, and suggest a possibility that SOD3 may function through modulating SIRT1 via the AMPK pathway in liver fibrosis.

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BACKGROUND Hepatocellular carcinoma (HCC) exhibits high invasiveness and mortality rates, and the molecular mechanisms of HCC have gained increasing research interest. The abnormal DNA damage response has long been recognized as one of the important factors for tumor occurrence and development. Recent studies have shown the potential of the protein RING finger and WD repeat domain 3 (RFWD3) that positively regulates p53 stability in response to DNA damage as a therapeutic target in cancers. AIM To investigate the relationship between HCC and RFWD3 in vitro and in vivo and explored the underlying molecular signalling transduction pathways. METHODS RFWD3 gene expression was analyzed in HCC tissues and adjacent normal tissues. Lentivirus was used to stably knockdown RFWD3 expression in HCC cell lines. After verifying the silencing efficiency, Celigo/cell cycle/apoptosis and MTT assays were used to evaluate cell proliferation and apoptosis. Subsequently, cell migration and invasion were assessed by wound healing and transwell assays. In addition, transduced cells were implanted subcutaneously and injected into the tail vein of nude mice to observe tumor growth and metastasis. Next, we used lentiviral-mediated rescue of RFWD3 shRNA to verify the phenotype. Finally, the microarray, ingenuity pathway analysis, and western blot analysis were used to analyze the regulatory network underlying HCC. RESULTS Compared with adjacent tissues, RFWD3 expression levels were significantly higher in clinical HCC tissues and correlated with tumor size and TNM stage ( P < 0.05), which indicated a poor prognosis state. RFWD3 silencing in BEL-7404 and HCC-LM3 cells increased apoptosis, decreased growth, and inhibited the migration in shRNAi cells compared with those in shCtrl cells ( P < 0.05). Furthermore, the in vitro results were supported by the findings of the in vivo experiments with the reduction of tumor cell invasion and migration. Moreover, the rescue of RFWD3 shRNAi resulted in the resumption of invasion and metastasis in HCC cell lines. Finally, gene expression profiling and subsequent experimental verification revealed that RFWD3 might influence the proliferation and metastasis of HCC via the Wnt/β-catenin signalling pathway. CONCLUSION We provide evidence for the expression and function of RFWD3 in HCC. RFWD3 affects the prognosis, proliferation, invasion, and metastasis of HCC by regulating the Wnt/β-catenin signalling pathway.

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