TitleMutational analysis of Ctnnb1 and Apc in tumors from rats given 1,2-dimethylhydrazine or 2-amino-3-methylimidazo[4,5-f]quinoline: mutational 'hotspots' and the relative expression of beta-catenin and c-jun.
Publication TypeJournal Article
Year of Publication2003
AuthorsBlum CA, Tanaka T, Zhong X, Li Q, Dashwood W-M, Pereira C, Xu M, Dashwood RH
JournalMol Carcinog
Volume36
Issue4
Pagination195-203
Date Published2003 Apr
ISSN0899-1987
Keywords1,2-Dimethylhydrazine, Animals, Base Sequence, beta Catenin, Carcinogens, Codon, Colonic Neoplasms, Consensus Sequence, Cytoskeletal Proteins, DNA Mutational Analysis, Genes, APC, Genes, jun, Intestinal Neoplasms, Liver Neoplasms, Male, Polymorphism, Single Nucleotide, Quinolines, Rats, Rats, Inbred F344, Skin Neoplasms, Trans-Activators
Abstract

There is growing interest in beta-catenin and its role in various human cancers. We recently reported that 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)- and 1,2-dimethylhydrazine (DMH)-induced colon tumors in the rat contain mutations in Ctnnb1, the gene for beta-catenin, but the mutation spectrum was influenced by postinitiation exposure to chlorophyllin (CHL) and indole-3-carbinol (I3C) [Blum et al., Carcinogenesis 2001;22:315-320]. The present paper describes a follow-up study in which all of the target organs for IQ- and DMH-induced tumorigenesis were screened; Ctnnb1 mutations were found in 44 of 119 DMH-induced colon tumors, six of 13 IQ-induced colon tumors, 28 of 81 DMH-induced small intestine tumors, none of five IQ-induced small intestine tumors, four of 106 IQ-induced liver tumors, none of 14 DMH-induced Zymbal's gland tumors, none of 24 IQ-induced Zymbal's gland tumors, and none of 29 IQ-induced skin tumors. In tumors from rats given carcinogen alone, or carcinogen plus CHL or I3C, Ctnnb1 mutations frequently substituted amino acids adjacent to Ser33, a critical Ser/Thr residue in the glycogen synthase kinase-3beta regulatory domain of beta-catenin. However, substitution of critical Ser/Thr residues themselves was detected in only three of 24 (12.5%) of the tumors from rats given carcinogen alone, compared with 23 of 58 (40%) of the tumors from rats given carcinogen and treated postinitiation with I3C or CHL (P < 0.02). More than 50 of the colon tumors with wild-type beta-catenin were examined further for their Apc status; the overall frequency of Apc mutations was <10%, and these genetic changes occurred exclusively in the 'Mutation Cluster Region' of Apc. A subset of colon tumors also was examined for expression of beta-catenin and c-jun; these proteins were overexpressed in all tumors containing Ctnnb1 mutations, but the expression was highest in tumors with Ctnnb1 mutations affecting Thr41 and Ser45 residues in the glycogen synthase kinase-3beta region of beta-catenin. Thus, Ctnnb1 mutations occurred more frequently than Apc mutations in colon and small intestine tumors of the rat, and certain mutations upregulated beta-catenin/T-cell factor target genes more effectively than others, perhaps influencing the response to phytochemicals administered postinitiation.

DOI10.1002/mc.10112
Alternate JournalMol. Carcinog.
PubMed ID12669311
PubMed Central IDPMC2279233
Grant ListR01 CA080176-03 / CA / NCI NIH HHS / United States
P30 ES00210 / ES / NIEHS NIH HHS / United States
R01 CA080176 / CA / NCI NIH HHS / United States
CA80176 / CA / NCI NIH HHS / United States
R29 CA065525 / CA / NCI NIH HHS / United States
R01 CA065525 / CA / NCI NIH HHS / United States
R01 CA065525-08 / CA / NCI NIH HHS / United States
R01 CA080176-02 / CA / NCI NIH HHS / United States
R01 CA065525-09 / CA / NCI NIH HHS / United States
T32ES07060 / ES / NIEHS NIH HHS / United States
R01 CA080176-05 / CA / NCI NIH HHS / United States
CA65525 / CA / NCI NIH HHS / United States
R01 CA065525-07 / CA / NCI NIH HHS / United States
R01 CA080176-04 / CA / NCI NIH HHS / United States
R01 CA065525-06A1 / CA / NCI NIH HHS / United States
T32 ES007060 / ES / NIEHS NIH HHS / United States
P30 ES000210 / ES / NIEHS NIH HHS / United States