title: P-glycoprotein down-regulates expression of breast cancer resistance protein in a drug-free state.
abstract: This study investigated whether P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) are linked in terms of expression. RT-PCR and Western blot analyses showed that the lung cancer cell line SK-MES-1/WT expressed BCRP. In a drug-free state, BCRP expression was significantly down-regulated in doxorubicin-resistant SK-MES-1/DX1000 cells overexpressing Pgp. Pharmacological inhibitors (PSC833 or verapamil) or siRNA for Pgp inhibited the down-regulation of BCRP, which was confirmed by confocal microscopy. PSC833 induced the phosphorylation of c-Jun NH2-terminal kinase (JNK) and c-Jun, while the JNK inhibitor SP600125 inhibited this effect. Dominant negative c-Jun decreased the expression of BCRP, but increased that of Pgp. These results indicate that Pgp down-regulates BCRP expression in a drug-free state in which JNK/c-Jun is involved.
authors.affiliation: Research Center for Resistant Cells and Department of Pharmacology, Chosun University Medical School, Gwangju, Republic of Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Bark
authors.forename: Hai-Dong
authors.initials: HD
authors.lastname: Xu
authors.forename: Sang-Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Jisoo
authors.initials: J
authors.lastname: Yun
authors.forename: Cheol-Hee
authors.initials: CH
authors.lastname: Choi
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000873:Anthracenes / Q000494:pharmacology; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D045744:Cell Line, Tumor; D003524:Cyclosporins / Q000494:pharmacology; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C116614:ABCG2 protein, human; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000873:Anthracenes; D000903:Antibiotics, Antineoplastic; D003524:Cyclosporins; D009363:Neoplasm Proteins; C432165:pyrazolanthrone; D004317:Doxorubicin; D048031:JNK Mitogen-Activated Protein Kinases; C070272:valspodar