Gefitinib ("Iressa", ZD1839), an epidermal growth factor receptor tyrosine kinase inhibitor, reverses breast cancer resistance protein/ABCG2-mediated drug resistance.
Gefitinib ("Iressa", ZD1839) is an orally active, selective epidermal growth factor receptor tyrosine kinase inhibitor, and the single agent is clinically effective in non-small cell lung cancer. Although gefitinib combined with various cytotoxic agents has been reported to enhance cytotoxicity in vitro and in mouse models, the mechanism remains undetermined. Here, to explore the mechanism with topoisomerase I inhibitors, we focused on the efflux pump of the breast cancer resistance protein (BCRP/ABCG2), and then examined whether gefitinib restored drug sensitivity in multidrug-resistant cancer cells overexpressing BCRP. We used PC-6 human small cell lung cancer cells and multidrug-resistant PC-6/SN2-5H cells selected with SN-38 of the active metabolite of irinotecan, and BCRP-overexpressing MCF-7/MX cells selected with mitoxantrone and BCRP cDNA transfectant MCF-7/clone 8 cells. Drug sensitivity against anticancer drugs was determined by tetrazolium dye assay, and intracellular topotecan accumulation by FACScan. The topotecan transport study was done using the plasma membrane vesicles of PC-6/SN2-5H cells. The resistant PC-6/SN2-5H cells overexpressed BCRP but not epidermal growth factor receptor mRNA. Ten micromoles of gefitinib reversed topotecan, SN-38, and mitoxantrone resistance, and increased the intracellular topotecan accumulation in the resistant cells but not in the parental cells. Furthermore, gefitinib inhibited the topotecan transport into the vesicles, and the K(i) value was 1.01 +/- 0.09 micromol/L in the Dixon plot analysis, indicating direct inhibition of BCRP by gefitinib. However, gefitinib was not transported into the vesicles with the high-performance liquid chromatography method. These results indicate that gefitinib reverses BCRP-mediated drug resistance by direct inhibition other than competitive inhibition as a BCRP substrate. Combination of gefitinib and topoisomerase I inhibitors could be clinically effective in cancers expressing BCRP.
Nakamura
Yoichi
Y
Second Department of Internal Medicine, Nagasaki University School of Medicine, Nagasaki, Japan.
Oka
Mikio
M
Soda
Hiroshi
H
Shiozawa
Ken
K
Yoshikawa
Megumi
M
Itoh
Akiko
A
Ikegami
Yoji
Y
Tsurutani
Junji
J
Nakatomi
Katsumi
K
Kitazaki
Takeshi
T
Doi
Seiji
S
Yoshida
Hisahiro
H
Kohno
Shigeru
S
D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001693:Biological Transport, Active; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D018288:Carcinoma, Small Cell / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D004815:Epidermal Growth Factor / Q000096:biosynthesis; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D000077156:Gefitinib; D006801:Humans; D020128:Inhibitory Concentration 50; D000077146:Irinotecan; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D008942:Mitoxantrone / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology*; D019772:Topotecan / Q000493:pharmacokinetics / Q000494:pharmacology
C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D009363:Neoplasm Proteins; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D004815:Epidermal Growth Factor; D000077146:Irinotecan; D019772:Topotecan; D000255:Adenosine Triphosphate; D008942:Mitoxantrone; D066246:ErbB Receptors; D000077156:Gefitinib; D002166:Camptothecin