title: New inhibitors of ABCG2 identified by high-throughput screening.
abstract: In order to identify novel inhibitors of the ATP-binding cassette transporter, ABCG2, a high-throughput assay measuring the accumulation of the ABCG2 substrate pheophorbide a in ABCG2-overexpressing NCI-H460 MX20 cells was used to screen libraries of compounds. Out of a library of 7,325 natural products and synthetic compounds from the National Cancer Institute/Developmental Therapeutics Program collection, 18 were found to inhibit ABCG2 at 10 micromol/L. After eliminating flavonoids and compounds of limited availability from the 18 original compounds, 10 of the 11 remaining compounds reversed mitoxantrone resistance in NCI-H460/MX20 cells and prevented ABCG2-mediated BODIPY-prazosin transport in ABCG2-transfected HEK293 cells, confirming an interaction with ABCG2. Based on the activity profiles and the availability of materials, five inhibitors were examined for their ability to compete with [(125)I]iodoarylazidoprazosin labeling of ABCG2, increase binding of the anti-ABCG2 antibody 5D3, and prevent P-glycoprotein or multidrug resistance protein 1-mediated transport. At a concentration of 20 micromol/L, all of the compounds reduced iodoarylazidoprazosin labeling by 50% to 80% compared with controls. All five compounds also increased 5D3 labeling of ABCG2, indicating that these compounds are inhibitors but not substrates of ABCG2. None of the compounds affected P-glycoprotein-mediated rhodamine 123 transport, whereas three affected multidrug resistance protein-1-mediated calcein transport at 25 mumol/L, suggesting that the compounds are relatively specific for ABCG2. These five novel inhibitors of ABCG2 activity may provide a basis for further investigation of ABCG2 function and its relevance in multidrug resistance.
authors: Basic Research Program, Science Applications International Corporation-Frederick, Inc., Building 560, Room 32-63A, NCI-Frederick, Frederick, MD 21702, USA. henrichc@ncifcrf.gov
authors: Curtis J
authors: CJ
authors: Henrich
authors: Robert W
authors: RW
authors: Robey
authors: Heidi R
authors: HR
authors: Bokesch
authors: Susan E
authors: SE
authors: Bates
authors: Suneet
authors: S
authors: Shukla
authors: Suresh V
authors: SV
authors: Ambudkar
authors: Michael
authors: M
authors: Dean
authors: James B
authors: JB
authors: McMahon
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors*; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000502:physiology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors*; D019920:Photoaffinity Labels
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D019920:Photoaffinity Labels; C116614:ABCG2 protein, human; C421109:multidrug resistance-associated protein 1