PIAS3/SOCS1-STAT3 axis responses to oxidative stress in hepatocellular cancer cells

The participation of STAT3 and its upstream inhibitors, PIAS3 and SOCS1, in the oxidative response of hepatocellular carcinoma (HCC) cells was uncertain. Here, the expression of PIAS3 and SOCS1 in HCC tissues and cell lines was explored, and we sought to determine whether oxidative stress epigenetically regulated PIAS3 and SOCS1 expression and STAT3 activation in HCC cells. The expression of PIAS3 and SOCS1 was markedly decreased in HCC cell lines and tissues compared to normal hepatic cells and tissues. In HCC patients, low PIAS3 and SOCS1 expression were associated with poor survival. Oxidative stress induced by H₂O₂ in HepG2 cells was indicated by low antioxidant levels and high protein carbonyl content. Moreover, oxidative stress in HepG2 cells contributed to reduced proliferation but increased apoptosis, migration, and invasion capacity, which might be counteracted by antioxidants, such as tocopheryl acetate (TA). PIAS3 and SOCS1 expression was markedly decreased, while STAT3 was activated in HepG2 cells in response to H₂O₂ exposure. Co-treatment with antioxidant TA effectively increased the expression of PIAS3 and SOCS1, but it dephosphorylated STAT3 in H₂O₂-treated cells. PIAS1 or SOCS1 overexpression in HepG2 cells after H₂O₂ treatment restored cell viability and anti-oxidative responses and decreased apoptosis, migration, and invasion ability, and dephosphorylated STAT3 levels. Co-administration of the STAT3 activator, colivelin, partially abolished the effect of PIAS3 and SOCS1 overexpression in these processes. Therefore, oxidative stress in HCC cells may improve their migration and reduce proliferation through STAT3 activation through the repression of PIAS3 and SOCS1 expression.