Becatecarin (rebeccamycin analog, NSC 655649) is a transport substrate and induces expression of the ATP-binding cassette transporter, ABCG2, in lung carcinoma cells.
OBJECTIVE
ABCG2 overexpression has been linked to resistance to topoisomerase inhibitors, leading us to examine the potential interaction between ABCG2 and becatecarin.


METHODS
Interaction with ABCG2 was determined by ATPase assay, competition of [(125)I]iodoarylazidoprazosin (IAAP) photolabeling and flow cytometry. Cellular resistance was measured in 4-day cytotoxicity assays. ABCG2 expression was measured by fluorescent-substrate transport assays and immunoblot.


RESULTS
Becatecarin competed [(125)I]-IAAP labeling of ABCG2, stimulated ATPase activity and, at concentrations greater than 10 microM, inhibited ABCG2-mediated transport. Becatecarin-selected A549 Bec150 lung carcinoma cells were 3.1-, 15-, 8-, and 6.8-fold resistant to becatecarin, mitoxantrone, SN-38 and topotecan, respectively. A549 Bec150 cells transported the ABCG2 substrates pheophorbide a, mitoxantrone and BODIPY-prazosin and displayed increased staining with the anti-ABCG2 antibody 5D3 compared to parental cells. Increased ABCG2 expression was confirmed by immunoblot.


CONCLUSIONS
Our results suggest that becatecarin is transported by ABCG2 and can induce ABCG2 expression in cancer cells.
Robey
Robert W
RW
Medical Oncology Branch, Center for Cancer Research, National Institutes of Health, Bethesda, MD 20892, USA. robeyr@mail.nih.gov
Obrzut
Tomasz
T
Shukla
Suneet
S
Polgar
Orsolya
O
Macalou
Sira
S
Bahr
Julian C
JC
Di Pietro
Attilio
A
Ambudkar
Suresh V
SV
Bates
Susan E
SE
D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000187:drug effects* / Q000235:genetics; D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism; D000970:Antineoplastic Agents / Q000493:pharmacokinetics / Q000494:pharmacology; D001386:Azides / Q000378:metabolism; D001692:Biological Transport; D002227:Carbazoles / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D005453:Fluorescence; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005960:Glucosides / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D006801:Humans; D015151:Immunoblotting; D007457:Iodine Radioisotopes; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D009363:Neoplasm Proteins / Q000187:drug effects* / Q000235:genetics; D011224:Prazosin / Q000031:analogs & derivatives / Q000378:metabolism
C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D001386:Azides; D002227:Carbazoles; D005960:Glucosides; D007457:Iodine Radioisotopes; D009363:Neoplasm Proteins; C041552:azidoprazosin; C093269:becatecarin; D000251:Adenosine Triphosphatases; D011224:Prazosin