title: Loss of hepatocyte growth factor/c-Met signaling pathway accelerates early stages of N-nitrosodiethylamine induced hepatocarcinogenesis.
abstract: Hepatocyte growth factor (HGF) has been reported to have both positive and negative effects on carcinogenesis. Here, we show that the loss of c-Met signaling in hepatocytes enhanced rather than suppressed the early stages of chemical hepatocarcinogenesis. c-Met conditional knockout mice (c-metfl/fl, AlbCre+/-; MetLivKO) treated with N-nitrosodiethylamine developed significantly more and bigger tumors and with a shorter latency compared with control (w/w, AlbCre+/-; Cre-Ctrl) mice. Accelerated tumor development was associated with increased rate of cell proliferation and prolonged activation of epidermal growth factor receptor (EGFR) signaling. MetLivKO livers treated with N-nitrosodiethylamine also displayed elevated lipid peroxidation, decreased ratio of reduced glutathione to oxidized glutathione, and up-regulation of superoxide dismutase 1 and heat shock protein 70, all consistent with increased oxidative stress. Likewise, gene expression profiling done at 3 and 5 months after N-nitrosodiethylamine treatment revealed up-regulation of genes associated with cell proliferation and stress responses in c-Met mutant livers. The negative effects of c-Met deficiency were reversed by chronic p.o. administration of antioxidant N-acetyl-L-cysteine. N-acetyl-L-cysteine blocked the EGFR activation and reduced the N-nitrosodiethylamine-initiated hepatocarcinogenesis to the levels of Cre-Ctrl mice. These results argue that intact HGF/c-Met signaling is essential for maintaining normal redox homeostasis in the liver and has tumor suppressor effect(s) during the early stages of N-nitrosodiethylamine-induced hepatocarcinogenesis.
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892-4262, USA.
authors.forename: Taro
authors.initials: T
authors.lastname: Takami
authors.forename: Pal
authors.initials: P
authors.lastname: Kaposi-Novak
authors.forename: Koichi
authors.initials: K
authors.lastname: Uchida
authors.forename: Luis E
authors.initials: LE
authors.lastname: Gomez-Quiroz
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Conner
authors.forename: Valentina M
authors.initials: VM
authors.lastname: Factor
authors.forename: Snorri S
authors.initials: SS
authors.lastname: Thorgeirsson
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D003043:Cocarcinogenesis; D004052:Diethylnitrosamine; D015972:Gene Expression Regulation, Neoplastic; D017228:Hepatocyte Growth Factor / Q000172:deficiency* / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D018384:Oxidative Stress; D019859:Proto-Oncogene Proteins c-met / Q000172:deficiency* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000975:Antioxidants; D004052:Diethylnitrosamine; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D000111:Acetylcysteine