title: Inhibition of the mitogen-activated protein kinase pathway results in the down-regulation of P-glycoprotein.
abstract: The multidrug resistance gene 1 (MDR1) product, P-glycoprotein (P-gp), pumps out a variety of anticancer agents from the cell, including anthracyclines, Vinca alkaloids, and taxanes. The expression of P-gp therefore confers resistance to these anticancer agents. In our present study, we found that FTI-277 (a farnesyltransferase inhibitor), U0126 [an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)], and 17-allylamino-17-demethoxygeldanamycin (an inhibitor of heat shock protein 90) reduced the endogenous expression levels of P-gp in the human colorectal cancer cells, HCT-15 and SW620-14. In contrast, inhibitors of phosphatidylinositol 3-OH kinase, mammalian target of rapamycin, p38 mitogen-activated protein kinase, and c-Jun NH(2)-terminal kinase did not affect P-gp expression in these cells. We further found that U0126 down-regulated exogenous P-gp expression in the MDR1-transduced human breast cancer cells, MCF-7/MDR and MDA-MB-231/MDR. However, the MDR1 mRNA levels in these cells were unaffected by this treatment. PD98059 (a MEK inhibitor), ERK small interfering RNA, and p90 ribosomal S6 kinase (RSK) small interfering RNA also suppressed P-gp expression. Conversely, epidermal growth factor and basic fibroblast growth factor enhanced P-gp expression, but the MDR1 mRNA levels were unchanged in epidermal growth factor-stimulated cells. Pulse-chase analysis revealed that U0126 promoted P-gp degradation but did not affect the biosynthesis of this gene product. The pretreatment of cells with U0126 enhanced the paclitaxel-induced cleavage of poly(ADP-ribose) polymerase and paclitaxel sensitivity. Furthermore, U0126-treated cells showed high levels of rhodamine123 uptake. Hence, our present data show that inhibition of the MEK-ERK-RSK pathway down-regulates P-gp expression levels and diminishes the cellular multidrug resistance.
authors.affiliation: Department of Chemotherapy, Kyoritsu University of Pharmacy, 1-5-30 Shibakoen, Minato-ku, Tokyo 105-8512, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Katayama
authors.forename: Sho
authors.initials: S
authors.lastname: Yoshioka
authors.forename: Satomi
authors.initials: S
authors.lastname: Tsukahara
authors.forename: Junko
authors.initials: J
authors.lastname: Mitsuhashi
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sugimoto
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics*; D002070:Butadienes / Q000494:pharmacology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D009570:Nitriles / Q000494:pharmacology; D017239:Paclitaxel / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D034622:RNA Interference; D020112:Rhodamine 123 / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002070:Butadienes; D009570:Nitriles; D047428:Protein Kinase Inhibitors; C113580:U 0126; D016222:Fibroblast Growth Factor 2; D020112:Rhodamine 123; D004815:Epidermal Growth Factor; D020928:Mitogen-Activated Protein Kinases; D017239:Paclitaxel