Sorafenib inhibits growth and metastasis of hepatocellular carcinoma by blocking STAT3

AIM: To investigate the inhibitory role and the underlying mechanisms of sorafenib on signal transducer and activator of transcription 3 (STAT3) activity in hepatocellular carcinoma (HCC).METHODS: Human and rat HCC cell lines were treated with sorafenib. Proliferation and STAT3 dephosphorylation were assessed. Potential molecular mechanisms of STAT3 pathway inhibition by sorafenib were evaluated. In vivo antitumor action and STAT3 inhibition were investigated in an immunocompetent orthotopic rat HCC model.RESULTS: Sorafenib decreased STAT3 phosphorylationat the tyrosine and serine residues (Y705 and S727), but did not affect Janus kinase 2 (JAK2) and phosphatase shatterproof 2 (SHP2), which is associated with growth inhibition in HCC cells. Dephosphorylation of S727 was associated with attenuated extracellular signal-regulated kinase (ERK) phosphorylation, similar to the effects of a mitogen-activated protein kinase (MEK) inhibitor U0126, suggesting that sorafenib induced S727 dephosphorylation by inhibiting MEK/ERK signaling. Meanwhile, sorafenib could also inhibit Akt phosphorylation, and both the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 and Akt knockdown resulted in Y705 dephosphorylation, indicating that Y705 dephosphorylation by sorafenib was mediated by inhibiting the PI3K/Akt pathway. Finally, in the rat HCC model, sorafenib signifi cantly inhibited STAT3 activity, reducing tumor growth and metastasis.CONCLUSION: Sorafenib inhibits growth and metastasis of HCC in part by blocking the MEK/ERK/STAT3 and PI3K/Akt/STAT3 signaling pathways, but independent of JAK2 and SHP2 activation.

Urolithin a alleviates oxidative stress-induced senescence in nucleus pulposus-derived mesenchymal stem cells through SIRT1/PGC-1α pathway

BACKGROUND In degenerative intervertebral disc(IVD),an unfavorable IVD environment leads to increased senescence of nucleus pulposus(NP)-derived mesenchymal stem cells(NPMSCs)and the inability to complete the differentiation from NPMSCs to NP cells,leading to further aggravation of IVD degeneration(IDD).Urolithin A(UA)has been proven to have obvious effects in delaying cell senescence and resisting oxidative stress.AIM To explore whether UA can alleviate NPMSCs senescence and to elucidate the underlying mechanism.METHODS In vitro,we harvested NPMSCs from rat tails,and divided NPMSCs into four groups:the control group,H2O2 group,H2O2+UA group,and H2O2+UA+SR-18292 group.Senescence-associatedβ-Galactosidase(SA-β-Gal)activity,cell cycle,cell proliferation ability,and the expression of senescence-related and silent information regulator of transcription 1/PPAR gamma coactivator-1α(SIRT1/PGC-1α)pathway-related proteins and mRNA were used to evaluate the protective effects of UA.In vivo,an animal model of IDD was constructed,and Xrays,magnetic resonance imaging,and histological analysis were used to assess whether UA could alleviate IDD in vivo.RESULTS We found that H2O2 can cause NPMSCs senescence changes,such as cell cycle arrest,reduced cell proliferation ability,increased SA-β-Gal activity,and increased expression of senescence-related proteins and mRNA.After UA pretreatment,the abovementioned senescence indicators were significantly alleviated.To further demonstrate the mechanism of UA,we evaluated the mitochondrial membrane potential and the SIRT1/PGC-1αpathway that regulates mitochondrial function.UA protected mitochondrial function and delayed NPMSCs senescence by activating the SIRT1/PGC-1αpathway.In vivo,we found that UA treatment alleviated an animal model of IDD by assessing the disc height index,Pfirrmann grade and the histological score.CONCLUSION In summary,UA could activate the SIRT1/PGC-1αsignaling pathway to protect mitochondrial function and alleviate cell senescence and IDD in vivo and vitro.