title: Hepatoprotective versus oncogenic functions of STAT3 in liver tumorigenesis.
abstract: Aberrantly hyperactivated STAT3 has been found in human liver cancers as an oncogene; however, STAT3 has also been shown to exert hepatoprotective effects during liver injury. The balancing act that STAT3 plays between hepatoprotection and liver tumorigenesis remains poorly defined. In this study, the diethylnitrosamine (DEN)-induced liver tumor model and the chronic carbon tetrachloride (CCl(4))-induced liver fibrosis model were both used to investigate the role of STAT3 in liver tumorigenesis. Hepatocyte-specific STAT3 knockout mice were resistant to liver tumorigenesis induced by a single DEN injection, whose tumorigenesis was associated with minimal chronic liver inflammation, injury, and fibrosis. In contrast, long-term CCl(4) treatment resulted in severe hepatic oxidative damage, inflammation, and fibrosis but rarely induced liver tumor formation in wild-type mice. Despite the oncogenic function of STAT3 in DEN-induced liver tumor, hepatocyte-specific STAT3 knockout mice were more susceptible to liver tumorigenesis after 16 weeks of CCl(4) injection, which was associated with higher levels of liver injury, inflammation, fibrosis, and oxidative DNA damage compared with wild-type mice. These findings suggest that the hepatoprotective feature of STAT3 prevents hepatic damage and fibrosis under the condition of persistent inflammatory stress, consequently suppressing injury-driven liver tumor initiation. Once liver tumor cells have developed, STAT3 likely acts as an oncogenic factor to promote tumor growth.
authors.affiliation: Laboratory of Liver Diseases, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.forename: Fouad
authors.initials: F
authors.lastname: Lafdil
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Ogyi
authors.initials: O
authors.lastname: Park
authors.forename: Shi
authors.initials: S
authors.lastname: Yin
authors.forename: Junyang
authors.initials: J
authors.lastname: Niu
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Miller
authors.forename: Zhaoli
authors.initials: Z
authors.lastname: Sun
authors.forename: Bin
authors.initials: B
authors.lastname: Gao
mesh_terms: D000818:Animals; D002251:Carbon Tetrachloride / Q000494:pharmacology; D004249:DNA Damage; D005355:Fibrosis; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic; D022781:Hepatocytes / Q000166:cytology; D007249:Inflammation; D008099:Liver / Q000378:metabolism*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D050796:STAT3 Transcription Factor / Q000378:metabolism*
chemical_list: D050796:STAT3 Transcription Factor; D002251:Carbon Tetrachloride