Overexpression of the ATP-binding Cassette Half-Transporter, ABCG2 (MXR/BCRP/ABCP1), in Flavopiridol-resistant Human Breast Cancer Cells

• Published in: Clinical cancer research Vol. 7; no. 1; pp. 145 - 152
• Main Authors: ROBEY, Robert W, MEDINA-PEREZ, Wilma Y, NISHIYAMA, Kenryu, LAHUSEN, Tyler, MIYAKE, Keisuke, LITMAN, Thomas, SENDEROWICZ, Adrian M, ROSS, Douglas D, BATES, Susan E
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.01.2001
• Subjects: Antineoplastic Agents - metabolism; Antineoplastic Agents - pharmacology; ATP Binding Cassette Transporter, Sub-Family B - antagonists & inhibitors; ATP Binding Cassette Transporter, Sub-Family B - metabolism; ATP Binding Cassette Transporter, Sub-Family G, Member 2; ATP-Binding Cassette Transporters - antagonists & inhibitors; ATP-Binding Cassette Transporters - biosynthesis; Biological and medical sciences; Blotting, Northern; Blotting, Western; Breast Neoplasms - drug therapy; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Cell Division - drug effects; DNA Primers - chemistry; Drug Resistance, Neoplasm; Flavonoids - pharmacology; Fluorescent Antibody Technique; Gynecology. Andrology. Obstetrics; Humans; Indoles - pharmacology; Mammary gland diseases; Medical sciences; Mitoxantrone - pharmacology; Mycotoxins - pharmacology; Neoplasm Proteins - antagonists & inhibitors; Neoplasm Proteins - biosynthesis; Piperidines - pharmacology; Polymerase Chain Reaction; Radiopharmaceuticals - metabolism; Tumor Cells, Cultured - drug effects; Tumor Cells, Cultured - metabolism; Tumor Cells, Cultured - pathology; Tumors; Human; Cytolysis; Enzyme; Gene product; Transferases; Glycoprotein; Enzyme inhibitor; Gene overexpression; Cytotoxicity; Malignant tumor; Gene expression; Outward current; In vitro; Resistance; Mammary gland diseases; Protein kinase; Multiple resistance; Established cell line; Mammary gland; Mechanism of action; ATP; ABC transporter; Tumor cell; Carrier protein
• ISSN: 1078-0432; 1557-3265

We sought to characterize the interactions of flavopiridol with members of the ATP-binding cassette (ABC) transporter family. Cells overexpressing multidrug resistance-1 (MDR-1) and multidrug resistance-associated protein (MRP) did not exhibit appreciable flavopiridol resistance, whereas cell lines overexpressing the ABC half-transporter, ABCG2 (MXR/BCRP/ABCP1), were found to be resistant to flavopiridol. Flavopiridol at a concentration of 10 μ m was able to prevent MRP-mediated calcein efflux, whereas Pgp-mediated transport of rhodamine 123 was unaffected at flavopiridol concentrations of up to 100 μ m . To determine putative mechanisms of resistance to flavopiridol, we exposed the human breast cancer cell line MCF-7 to incrementally increasing concentrations of flavopiridol. The resulting resistant subline, MCF-7 FLV1000, is maintained in 1000 n m flavopiridol and was found to be 24-fold resistant to flavopiridol, as well as highly cross-resistant to mitoxantrone (675-fold), topotecan (423-fold), and SN-38 (950-fold), the active metabolite of irinotecan. Because this cross-resistance pattern is consistent with that reported for ABCG2-overexpressing cells, cytotoxicity studies were repeated in the presence of 5μ m of the ABCG2 inhibitor fumitremorgin C (FTC), and sensitivity of MCF-7 FLV1000 cells to flavopiridol, mitoxantrone, SN-38, and topotecan was restored. Mitoxantrone efflux studies were performed, and high levels of FTC-reversible mitoxantrone efflux were found. Northern blot and PCR analysis revealed overexpression of the ABCG2 gene. Western blot confirmed overexpression of ABCG2; neither P-glycoprotein nor MRP overexpression was detected. These results suggest that ABCG2 plays a role in resistance to flavopiridol.