title: Reduced ATM kinase activity and an attenuated p53 response to DNA damage in carcinogen-induced preneoplastic hepatic lesions in the rat.
abstract: In previous studies we have demonstrated that the p53 response to DNA damage in preneoplastic liver lesions, referred to as enzyme-altered foci (EAF), is attenuated. In the present investigation comparative quantitative RT-PCR revealed no major difference in the p53 mRNA levels in EAF and non-EAF tissue. When CoCl(2) was employed to induce hypoxia-inducible factor (HIF-1alpha), both non-EAF and EAF hepatocytes readily accumulated p53, whereas EAF hepatocytes did not accumulate p53 upon treatment with diethylnitrosamine (DEN). The p53 response was also induced in EAF hepatocytes by the inhibitor of nuclear export, leptomycin B. An inhibitor of DNA-dependent protein kinase (DNA-PK) and ataxia telangiectasia mutated (ATM), wortmannin, blocked the DEN-induced p53 response in non-EAF hepatocytes. Assay of kinase activity in immunoprecipitated material from EAF and non-EAF tissue revealed attenuated ATM activity in EAF. Immunohistological and western blot analysis of the level of ATM protein was in agreement with the activity measurements and no phosphorylation of Ser15 in p53 was detected in EAF tissue 24 h after a challenging dose of DEN. Taken together with previously published data, these data indicate selective attenuation of the DNA damage pathway in EAF hepatocytes. Down-regulation of DNA damage-induced and ATM-mediated phosphorylation of p53 may confer a growth advantage on EAF hepatocytes.
authors.affiliation: Occupational Toxicology Group, Institute of Environmental Medicine, Karolinska Institutet, S-171 77 Stockholm, Sweden.
authors.forename: I
authors.initials: I
authors.lastname: Silins
authors.forename: N
authors.initials: N
authors.lastname: Finnberg
authors.forename: A
authors.initials: A
authors.lastname: Ståhl
authors.forename: J
authors.initials: J
authors.lastname: Högberg
authors.forename: U
authors.initials: U
authors.lastname: Stenius
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D002110:Caffeine / Q000494:pharmacology; D002273:Carcinogens / Q000494:pharmacology*; D018797:Cell Cycle Proteins; D003035:Cobalt / Q000494:pharmacology; D004249:DNA Damage / Q000187:drug effects* / Q000235:genetics; D004268:DNA-Binding Proteins; D004052:Diethylnitrosamine / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005260:Female; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011230:Precancerous Conditions / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D002273:Carcinogens; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005231:Fatty Acids, Unsaturated; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D003035:Cobalt; D002110:Caffeine; D004052:Diethylnitrosamine; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; C018021:cobaltous chloride; D000077191:Wortmannin; C038753:leptomycin B