title: Coordinated induction of MRP/GS-X pump and gamma-glutamylcysteine synthetase by heavy metals in human leukemia cells.
abstract: We recently reported that GS-X pump activity, as assessed by ATP-dependent transport of the glutathione-platinum complex and leukotriene C4, and intracellular glutathione (GSH) levels were remarkably enhanced in cis-diamminedichloroplatinum(II) (cisplatin)-resistant human leukemia HL-60 cells (Ishikawa, T., Wright, C. D., and Ishizuka, H. (1994) J. Biol. Chem. 269, 29085-29093). Now, using Northern hybridization and RNase protection assay, we provide evidence that the multidrug resistance-associated protein (MRP) gene, which encodes a human GS-X pump, is expressed at higher levels in cisplatin-resistant (HL-60/R-CP) cells than in sensitive cells, whereas amplification of the MRP gene is not detected by Southern hybridization. Culturing HL-60/R-CP cells in cisplatin-free medium resulted in reduced MRP mRNA levels, but these levels could be induced to rise within 30 h by cisplatin and heavy metals such as arsenite, cadmium, and zinc. The increased levels of MRP mRNA were closely related with enhanced activities of ATP-dependent transport of leukotriene C4 (LTC4) in plasma membrane vesicles. The glutathione-platinum (GS-Pt) complex, but not cisplatin, inhibited ATP-dependent LTC4 transport, suggesting that the MRP/GS-X pump transports both LTC4 and the GS-Pt complex. Expression of gamma-glutamylcysteine synthetase in the cisplatin-resistant cells was also co-induced within 24 h in response to cisplatin exposure, resulting in a significant increase in cellular GSH level. The resistant cells exposed to cisplatin were cross-resistant to melphalan, chlorambucil, arsenite, and cadmium. These observations suggest that elevated expression of the MRP/GS-X pump and increased GSH biosynthesis together may be important factors in the cellular metabolism and disposition of cisplatin, alkylating agents, and heavy metals.
authors.affiliation: Department of Experimental Pediatrics and Section of Eucaryotic Cell Research, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: J J
authors.initials: JJ
authors.lastname: Bao
authors.forename: Y
authors.initials: Y
authors.lastname: Yamane
authors.forename: K
authors.initials: K
authors.lastname: Akimaru
authors.forename: K
authors.initials: K
authors.lastname: Frindrich
authors.forename: C D
authors.initials: CD
authors.lastname: Wright
authors.forename: M T
authors.initials: MT
authors.lastname: Kuo
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D000970:Antineoplastic Agents / Q000633:toxicity; D018053:Arsenites / Q000494:pharmacology*; D001483:Base Sequence; D002104:Cadmium / Q000494:pharmacology*; D002352:Carrier Proteins / Q000096:biosynthesis*; D002455:Cell Division / Q000187:drug effects; D002699:Chlorambucil / Q000633:toxicity; D002945:Cisplatin / Q000633:toxicity; D017931:DNA Primers; D018432:Drug Resistance, Multiple; D004790:Enzyme Induction; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis*; D005978:Glutathione / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D007700:Kinetics; D008558:Melphalan / Q000633:toxicity; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins / Q000096:biosynthesis; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D018053:Arsenites; D002104:Cadmium; D002352:Carrier Proteins; D002699:Chlorambucil; D002945:Cisplatin; D017931:DNA Primers; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D008558:Melphalan; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D015032:Zinc; C086860:glutathione transporter; C015001:arsenite