title: Moderate increase in Mdr1a/1b expression causes in vivo resistance to doxorubicin in a mouse model for hereditary breast cancer.
abstract: We have found previously that acquired doxorubicin resistance in a genetically engineered mouse model for BRCA1-related breast cancer was associated with increased expression of the mouse multidrug resistance (Mdr1) genes, which encode the drug efflux transporter ATP-binding cassette B1/P-glycoprotein (P-gp). Here, we show that even moderate increases of Mdr1 expression (as low as 5-fold) are sufficient to cause doxorubicin resistance. These moderately elevated tumor P-gp levels are below those found in some normal tissues, such as the gut. The resistant phenotype could be completely reversed by the third-generation P-gp inhibitor tariquidar, which provides a useful strategy to circumvent this type of acquired doxorubicin resistance. The presence of MDR1A in drug-resistant tumors with a moderate increase in Mdr1a transcripts could be shown with a newly generated chicken antibody against a mouse P-gp peptide. Our data show the usefulness of realistic preclinical models to characterize levels of Mdr1 gene expression that are sufficient to cause resistance.
authors: Division of Molecular Biology and Centre for Biomedical Genetics, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Marina
authors: M
authors: Pajic
authors: Jayasree K
authors: JK
authors: Iyer
authors: Ariena
authors: A
authors: Kersbergen
authors: Eline
authors: E
authors: van der Burg
authors: Anders O H
authors: AO
authors: Nygren
authors: Jos
authors: J
authors: Jonkers
authors: Piet
authors: P
authors: Borst
authors: Sven
authors: S
authors: Rottenberg
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000494:pharmacology / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D019398:Genes, BRCA1; D016158:Genes, p53; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D011804:Quinolines / Q000494:pharmacology; D047368:Tumor Burden; D015854:Up-Regulation / Q000502:physiology; D000097202:ATP-Binding Cassette Sub-Family B Member 4
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000903:Antibiotics, Antineoplastic; D004317:Doxorubicin; D011804:Quinolines; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C095122:multidrug resistance protein 3; C402343:tariquidar