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Downregulation of breast cancer resistance protein in colon adenomas reduces cellular xenobiotic resistance and leads to accumulation of a food‐derived carcinogen
Author(s) -
Dietrich Christoph G.,
Vehr AnnKathrin,
Martin Ina V.,
Gaßler Nikolaus,
Rath Timo,
Roeb Elke,
Schmitt Johannes,
Trautwein Christian,
Geier Andreas
Publication year - 2011
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.25958
Subject(s) - downregulation and upregulation , abcg2 , adenoma , carcinogen , cancer research , colorectal cancer , immunohistochemistry , real time polymerase chain reaction , biology , cancer , medicine , endocrinology , pathology , atp binding cassette transporter , transporter , gene , biochemistry
Several molecular changes in colorectal adenomas provide the basis of the adenoma–carcinoma sequence. We investigated the expression of xenobiotic ATP‐binding cassette (ABC) transporters in humans and in ApcMin mice and conducted functional studies estimating the importance of the expression changes. Twenty‐nine adenomas from 21 patients and eight adenomas from four ApcMin mice were analyzed using Western blotting and quantitative Real‐time polymerase chain reaction (RT‐PCR). Adjacent healthy tissue served as control for each polyp. Breast cancer resistance protein (BCRP) was significantly downregulated in human colorectal adenomas (to 28 ± 35% of adjacent healthy tissue). This was in line with data from ApcMin mice adenomas, where downregulation was significant as well (to 58 ± 34%). In parallel, quantitative RT‐PCR showed BCRP mRNA downregulation in human adenomas (to 17 ± 31%). Basal multidrug resistance‐associated protein 2 expression was low and did not change in adenomas; multidrug resistance transporter 1 expression also did not differ between adenomas and healthy tissue. In a functional study, ApcMin mice received radioactively labelled 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐β] pyridine (PhIP), a food colon carcinogen and substrate of BCRP, by oral gavage with analysis of PhIP accumulation and DNA adduct formation 48 hr later. In this setting, we could demonstrate a higher carcinogen concentration in adenomas of ApcMin mice (181 ± 113% of normal tissue) including immunohistochemical detection of PhIP–DNA adducts. We conclude that significant transcriptional downregulation of BCRP/Bcrp leads to higher carcinogen concentrations in colorectal adenomas of mice and men. This might promote the adenoma–carcinoma sequence by higher genotoxic effects. The results indicate a possible role of transporter deficiencies in susceptibility for colon carcinoma.