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Mucin‐depleted foci have β‐catenin gene mutations, altered expression of its protein, and are dose‐ and time‐dependent in the colon of 1,2‐dimethylhydrazine‐treated rats
Author(s) -
Femia Angelo Pietro,
Bendinelli Benedetta,
Giannini Augusto,
Salvadori Maddalena,
Pinzani Pamela,
Dolara Piero,
Caderni Giovanna
Publication year - 2005
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.20981
Subject(s) - 1,2 dimethylhydrazine , aberrant crypt foci , carcinogenesis , immunohistochemistry , mucin , catenin , crypt , pathology , carcinogen , mucin 2 , gene mutation , mutation , microbiology and biotechnology , azoxymethane , biology , gene expression , gene , chemistry , cancer research , colorectal cancer , medicine , endocrinology , biochemistry , cancer , wnt signaling pathway , genetics , colonic disease
Mucin‐depleted foci (MDF) are purported preneoplastic lesions that can be easily visualized in the unsectioned colon of carcinogen‐treated rats stained with high‐iron diamine alcian blue (HID‐AB). In F344 rats treated twice with 150 mg/kg of 1,2‐dimethylhydrazine (DMH) and sacrificed after 5, 9, 13 and 28 weeks, MDF increased over time from 5 to 13 weeks, whereas they decreased at 28 weeks, when tumors appear. MDF multiplicity (crypts/MDF) linearly increased with time. Increasing doses of DMH (100, 150 and 200 mg/kg × 2 times) caused a dose‐related increase in MDF. Mutations in Ctnnb1 gene codifying for β‐catenin were identified with PCR amplification and direct sequencing in 6/15 tumors (40%), 7/28 MDF (25%) and 2/27 (7%) aberrant crypt foci (ACF) identified in HID‐AB‐stained colon. All mutations in tumors and MDF caused amino acid substitution, while one mutation in ACF was silent. β‐catenin detected at membrane level by immunohistochemistry was markedly reduced in MDF and tumors and, to a lesser extent, in ACF identified with HID‐AB. By contrast, nuclear localization of β‐catenin was significantly increased in MDF and tumors, while no variation was observed in ACF. β‐catenin cytoplasmic expression was also significantly increased in MDF and tumors but to a lesser extent in ACF. In conclusion, MDF are induced dose‐dependently by DMH, increase in size with time, have mutations in the β‐catenin gene and marked alterations in β‐catenin cellular localization. Since all these phenomena are considered specific steps for colon tumorigenesis, these results further support the hypothesis that MDF are cancer precursors and can be proposed as endpoints in short‐term carcinogenesis experiments. © 2005 Wiley‐Liss, Inc.