title: Transient induction of the MRP/GS-X pump and gamma-glutamylcysteine synthetase by 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3- nitrosourea in human glioma cells.
abstract: Treatment of human glioma A172 cells with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU), an alkylating antitumor agent the primary target of which has been thought to be DNA, resulted in elevated expression of mRNA for multidrug resistance-associated protein (MRP) within the first 2 h and then a decrease in expression 24 h after the treatment. Western blot analyses revealed that levels of MRP in these ACNU-treated cells paralleled mRNA levels. Membrane vesicles prepared from ACNU-treated cells also displayed elevated transport activities for leukotriene C4, a known substrate for MRP. Gamma-glutamylcysteine synthetase (gamma-GCS) mRNA expression was coinduced with MRP by ACNU. Because gamma-GCS is the rate-limiting enzyme involved in the de novo biosynthesis of glutathione, increases in glutathione were also transiently induced by ACNU. These results demonstrate for the first time that the expression of functional MRP and gamma-GCS can be transiently coinduced by ACNU. Multiple short exposures (1 h) of ACNU following a long duration (1 week) of drug-free conditions resulted in the development of an ACNU-resistant population (designated A172R) that overexpressed MRP/gamma-GCS mRNA and had elevated transport activities for leukotriene C4. A172R exhibited cross-resistance to the antitumor drug doxorubicin and heavy metal sodium arsenate but not to cisplatin. Our results also demonstrate that intermittent treatments of human glioma cells with ACNU can lead to the development of MRP-related multidrug resistance. These results, taken together, reveal a possible new mechanism of the development of drug resistance for the antitumor nitrosoureas.
authors.affiliation: Department of Molecular Pathology, The University of Texas, M. D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: A
authors.initials: A
authors.lastname: Gomi
authors.forename: S
authors.initials: S
authors.lastname: Shinoda
authors.forename: T
authors.initials: T
authors.lastname: Masuzawa
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: M T
authors.initials: MT
authors.lastname: Kuo
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000032:analysis / Q000096:biosynthesis*; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001149:Arsenates / Q000633:toxicity; D001692:Biological Transport; D002352:Carrier Proteins / Q000032:analysis / Q000096:biosynthesis*; D002945:Cisplatin / Q000633:toxicity; D004317:Doxorubicin / Q000633:toxicity; D018432:Drug Resistance, Multiple; D004790:Enzyme Induction; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D005910:Glioma / Q000378:metabolism*; D005721:Glutamate-Cysteine Ligase / Q000032:analysis / Q000096:biosynthesis*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D017997:Leukotriene C4 / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D008969:Molecular Sequence Data; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D015376:Nimustine / Q000494:pharmacology*; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
chemical_list: D018528:ATP-Binding Cassette Transporters; D000906:Antibodies; D000970:Antineoplastic Agents; D001149:Arsenates; D002352:Carrier Proteins; D002945:Cisplatin; D004317:Doxorubicin; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D017997:Leukotriene C4; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D015376:Nimustine; D010446:Peptide Fragments; D012333:RNA, Messenger; C086860:glutathione transporter; C009277:sodium arsenate