title: Metformin prevents liver tumorigenesis by inhibiting pathways driving hepatic lipogenesis.
abstract: A number of factors have been identified that increase the risk of hepatocellular carcinoma (HCC). Recently it has become appreciated that type II diabetes increases the risk of developing HCC. This represents a patient population that can be identified and targeted for cancer prevention. The biguanide metformin is a first-line therapy for the treatment of type II diabetes in which it exerts its effects primarily on the liver. A role of metformin in HCC is suggested by studies linking metformin intake for control of diabetes with a reduced risk of HCC. Although a number of preclinical studies show the anticancer properties of metformin in a number of tissues, no studies have directly examined the effect of metformin on preventing carcinogenesis in the liver, one of its main sites of action. We show in these studies that metformin protected mice against chemically induced liver tumors. Interestingly, metformin did not increase AMPK activation, often shown to be a metformin target. Rather metformin decreased the expression of several lipogenic enzymes and lipogenesis. In addition, restoring lipogenic gene expression by ectopic expression of the lipogenic transcription factor SREBP1c rescues metformin-mediated growth inhibition. This mechanism of action suggests that metformin may also be useful for patients with other disorders associated with HCC in which increased lipid synthesis is observed. As a whole these studies show that metformin prevents HCC and that metformin should be evaluated as a preventive agent for HCC in readily identifiable at-risk patients.
authors.affiliation: Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore Maryland 21201, USA.
authors.forename: Kavita
authors.initials: K
authors.lastname: Bhalla
authors.forename: Bor Jang
authors.initials: BJ
authors.lastname: Hwang
authors.forename: Ruby E
authors.initials: RE
authors.lastname: Dewi
authors.forename: William
authors.initials: W
authors.lastname: Twaddel
authors.forename: Olga G
authors.initials: OG
authors.lastname: Goloubeva
authors.forename: Kwok-Kin
authors.initials: KK
authors.lastname: Wong
authors.forename: Neeraj K
authors.initials: NK
authors.lastname: Saxena
authors.forename: Shyam
authors.initials: S
authors.lastname: Biswal
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Girnun
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008055:Lipids / Q000737:chemistry; D050155:Lipogenesis; D008099:Liver / Q000378:metabolism*; D008113:Liver Neoplasms / Q000378:metabolism; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009369:Neoplasms / Q000517:prevention & control*; D051381:Rats; D051780:Sterol Regulatory Element Binding Protein 1 / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
chemical_list: D007004:Hypoglycemic Agents; D008055:Lipids; C497388:Srebf1 protein, mouse; D051780:Sterol Regulatory Element Binding Protein 1; D014280:Triglycerides; D008687:Metformin; D055372:AMP-Activated Protein Kinases