title: Paclitaxel-resistance conferred by altered expression of efflux and influx transporters for paclitaxel in the human hepatoma cell line, HepG2.
abstract: Paclitaxel-resistant HepG2 (PR-HepG2) cells were established by long-term exposure of HepG2 cells to paclitaxel and expression and function of efflux (P-glycoprotein, MRP2) and influx (OATP1B3) transporters for paclitaxel were examined to understand the mechanisms underlying the resistance. mRNA expression of P-glycoprotein (P-gp) increased in PR-HepG2 more than in HepG2 cells, while that of MRP2 did not change. Interestingly, mRNA expression of OATP1B3 drastically decreased in PR-HepG2 cells. [(3)H]Paclitaxel uptake was less in PR-HepG2 than in HepG2 cells and the uptake in both cells increased by metabolic inhibition. The uptake of [(3)H]paclitaxel and rhodamine 123 increased by verapamil, a P-gp inhibitor. Probenecid, an MRP inhibitor, did not affect [(3)H]paclitaxel uptake in both cells. Sulfobromophthalein, an OATP1B3 inhibitor, inhibited [(3)H]paclitaxel uptake in HepG2 but not in PR-HepG2 cells. Cytotoxicity studies showed that the resistance of PR-HepG2 cells to paclitaxel was reversed by verapamil. PR-HepG2 cells showed cross-resistance to doxorubicin, a P-gp substrate, but not to cisplatin. These results indicate that enhanced expression and function of P-gp may be a predominant mechanism of paclitaxel resistance in PR-HepG2 cells and the reduced influx via OATP1B3 may also serve to lower intracellular paclitaxel concentration in cooperation with P-gp-mediated efflux.
authors.affiliation: Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan. takanom@hiroshima-u.ac.jp
authors.forename: Mikihisa
authors.initials: M
authors.lastname: Takano
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Otani
authors.forename: Minori
authors.initials: M
authors.lastname: Tanda
authors.forename: Masashi
authors.initials: M
authors.lastname: Kawami
authors.forename: Junya
authors.initials: J
authors.lastname: Nagai
authors.forename: Ryoko
authors.initials: R
authors.lastname: Yumoto
mesh_terms: D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis; D029362:Organic Anion Transporters, Sodium-Independent / Q000502:physiology; D017239:Paclitaxel / Q000378:metabolism / Q000494:pharmacology*; D011339:Probenecid / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D020112:Rhodamine 123 / Q000378:metabolism; D019810:Sodium Azide / Q000494:pharmacology; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; D013448:Sulfobromophthalein / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D004317:Doxorubicin; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D029362:Organic Anion Transporters, Sodium-Independent; D017239:Paclitaxel; D011339:Probenecid; D012333:RNA, Messenger; D020112:Rhodamine 123; D019810:Sodium Azide; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; D013448:Sulfobromophthalein; D014700:Verapamil; C000715087:ABCC2 protein, human; C421209:SLCO1B3 protein, human