title: In vitro and in vivo identification of ABCB1 as an efflux transporter of bosutinib.
abstract: BACKGROUND
  Bosutinib is a recently approved ABL inhibitor. In spite of the well-documented effectiveness of BCR-ABL inhibitors in treating chronic myeloid leukemia, development of resistance is a continuous clinical challenge. Transporters that facilitate drug uptake and efflux have been proposed as one potential source of resistance to tyrosine kinase inhibitor treatment. Our aim was to determine which carriers are responsible for bosutinib transport.
  
  
  METHODS
  K562S cells overexpressing the drug transporters ABCB1, ABCG2, and SLC22A1 were generated, characterized and used in proliferation assay and intracellular uptake and retention assay (IUR). In vivo experiments were performed in nude mice injected with K562S, K562DOX cells (overexpressing ABCB1), and K562DOX silenced for ABCB1 (K562DOX/sh P-GP).
  
  
  RESULTS
  The IUR assay using C-14 bosutinib showed that only ABCB1 was responsible for active bosutinib transport. K562DOX cells showed the lowest intracellular level of bosutinib, while K562DOX cells treated with the ABCB1 inhibitor verapamil showed intracellular bosutinib levels comparable with parental K562S. Proliferation assays demonstrated that K562DOX are resistant to bosutinib treatment while verapamil is able to restore the sensitivity to the drug. Nude mice injected with K562DOX and treated with bosutinib showed very limited response and quickly relapsed after stopping treatment while K562S as well as K562DOX/sh P-GP remained tumor-free.
  
  
  CONCLUSIONS
  Our data suggest that the analysis of ABCB1 expression levels might help determine treatment options for patients exhibiting resistance to bosutinib.
authors.affiliation: Department of Health sciences, University of Milano-Bicocca, S.Gerardo Hospital, Monza, Italy. sara.redaelli@unimib.it.
authors.forename: Sara
authors.initials: S
authors.lastname: Redaelli
authors.affiliation: Department of Health sciences, University of Milano-Bicocca, S.Gerardo Hospital, Monza, Italy. perini.pietro@gmail.com.
authors.forename: Pietro
authors.initials: P
authors.lastname: Perini
authors.affiliation: Department of Health sciences, University of Milano-Bicocca, S.Gerardo Hospital, Monza, Italy. monica.ceccon@unimib.it.
authors.forename: Monica
authors.initials: M
authors.lastname: Ceccon
authors.affiliation: Department of Health sciences, University of Milano-Bicocca, S.Gerardo Hospital, Monza, Italy. rocco.piazza@unimib.it.
authors.forename: Rocco
authors.initials: R
authors.lastname: Piazza
authors.affiliation: Department of Surgery and Translational Medicine, University of Milano-Bicocca, Monza, Italy. roberta.rigolio@unimib.it.
authors.forename: Roberta
authors.initials: R
authors.lastname: Rigolio
authors.affiliation: Department of Health sciences, University of Milano-Bicocca, S.Gerardo Hospital, Monza, Italy. mario.mauri@unimib.it.
authors.forename: Mario
authors.initials: M
authors.lastname: Mauri
authors.affiliation: Department of Oncology, Pfizer Research, Pearl River, New City, NY, USA. fboschelli@icloud.com.
authors.forename: Frank
authors.initials: F
authors.lastname: Boschelli
authors.affiliation: Institute of Translational Medicine, Molecular and Clinical Cancer Medicine, University of Liverpool, Liverpool, UK. A.Giannoudis@liverpool.ac.uk.
authors.forename: Athina
authors.initials: A
authors.lastname: Giannoudis
authors.affiliation: Department of Health sciences, University of Milano-Bicocca, S.Gerardo Hospital, Monza, Italy. carlo.gambacorti@unimib.it.
authors.forename: Carlo
authors.initials: C
authors.lastname: Gambacorti-Passerini
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000187:drug effects; D000814:Aniline Compounds / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy*; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D009570:Nitriles / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D011804:Quinolines / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D014162:Transfection
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D000814:Aniline Compounds; D009570:Nitriles; D011804:Quinolines; C471992:bosutinib