Hepatoprotective versus Oncogenic Functions of STAT3 in Liver Tumorigenesis

• Published in: The American journal of pathology Vol. 179; no. 2; pp. 714 - 724
• Main Authors: Wang, Hua, Lafdil, Fouad, Wang, Lei, Park, Ogyi, Yin, Shi, Niu, Junyang, Miller, Andrew M, Sun, Zhaoli, Gao, Bin
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.08.2011; American Society for Investigative Pathology
• Subjects: Animals; Biological and medical sciences; Carbon Tetrachloride - pharmacology; DNA Damage; Fibrosis; Gene Deletion; Gene Expression Regulation, Neoplastic; Hepatocytes - cytology; Inflammation; Investigative techniques, diagnostic techniques (general aspects); Liver - metabolism; Liver Neoplasms - genetics; Liver Neoplasms - metabolism; Male; Medical sciences; Mice; Mice, Knockout; Mice, Transgenic; Pathology; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Real-Time Polymerase Chain Reaction - methods; Regular; STAT3 Transcription Factor - metabolism; Carcinogen; Anatomic pathology; Digestive system; Liver; Transcription factor STAT3; Tumorigenicity; Carcinogenesis; Comparative study
• ISSN: 0002-9440; 1525-2191
• DOI: 10.1016/j.ajpath.2011.05.005

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 (CCl4 )–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 CCl4 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 CCl4 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.