title: Loss of metallothionein predisposes mice to diethylnitrosamine-induced hepatocarcinogenesis by activating NF-kappaB target genes.
abstract: Metallothioneins (MT) are potent scavengers of free radicals that are silenced in primary hepatocellular carcinomas (HCC) of human and rodent origin. To examine whether loss of MT promotes hepatocarcinogenesis, male Mt-1 and Mt-2 double knockout (MTKO) and wild-type (WT) mice were exposed to diethylnitrosamine (DEN) and induction of HCC was monitored at 23 and 33 weeks. The size and number of liver tumors, the ratio between liver and body weight, and liver damage were markedly elevated in the MTKO mice at both time points compared with the WT mice. At 23 weeks, MTKO mice developed HCC whereas WT mice developed only preneoplastic nodules suggesting that loss of MT accelerates hepatocarcinogenesis. MTKO tumors also exhibited higher superoxide anion levels. Although NF-κB activity increased in the liver nuclear extracts of both genotypes after DEN exposure, the complex formed in MTKO mice was predominantly p50/65 heterodimer (transcriptional activator) as opposed to p50 homodimer (transcriptional repressor) in WT mice. Phosphorylation of p65 at Ser276 causing its activation was also significantly augmented in DEN-exposed MTKO livers. NF-κB targets that include early growth response genes and proinflammatory cytokines were significantly upregulated in MTKO mice. Concurrently, there was a remarkable increase (∼100-fold) in Pai-1 expression; significant increase in c-Jun, c-Fos, c-Myc, Ets2, and ATF3 expressions; and growth factor signaling that probably contributed to the increased tumor growth in MTKO mice. Taken together, these results demonstrate that MTs protect mice from hepatocarcinogen-induced liver damage and carcinogenesis, underscoring their potential therapeutic application against hepatocellular cancer.
authors.affiliation: Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio, USA. sarmila.majumder@osumc.edu
authors.forename: Sarmila
authors.initials: S
authors.lastname: Majumder
authors.forename: Satavisha
authors.initials: S
authors.lastname: Roy
authors.forename: Thomas
authors.initials: T
authors.lastname: Kaffenberger
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.forename: Stefan
authors.initials: S
authors.lastname: Costinean
authors.forename: Wendy
authors.initials: W
authors.lastname: Frankel
authors.forename: Anna
authors.initials: A
authors.lastname: Bratasz
authors.forename: Periannan
authors.initials: P
authors.lastname: Kuppusamy
authors.forename: Tsonwin
authors.initials: T
authors.lastname: Hai
authors.forename: Kalpana
authors.initials: K
authors.lastname: Ghoshal
authors.forename: Samson T
authors.initials: ST
authors.lastname: Jacob
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism*; D004052:Diethylnitrosamine; D015972:Gene Expression Regulation, Neoplastic; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008668:Metallothionein / Q000172:deficiency* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011519:Proto-Oncogenes; D058258:Serpin E2 / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D013481:Superoxides / Q000378:metabolism
chemical_list: D016328:NF-kappa B; D010982:Platelet-Derived Growth Factor; D058258:Serpin E2; C511869:Serpine2 protein, mouse; D013481:Superoxides; D004052:Diethylnitrosamine; D008668:Metallothionein; D020928:Mitogen-Activated Protein Kinases