Up-regulation of gamma-glutamylcysteine synthetase activity in melphalan-resistant human multiple myeloma cells expressing increased glutathione levels. 1994

R T Mulcahy, and H H Bailey, and J J Gipp
Department of Human Oncology, University of Wisconsin Comprehensive Cancer Center, University of Wisconsin-Madison 53792.

Levels of intracellular glutathione (GSH) and the GSH-related enzymes gamma-glutamylcysteine synthetase (gamma-GCS) and gamma-glutamyltranspeptidase (gamma-GT) were measured in the melphalan-resistant human multiple myeloma cell line 8226/LR-5 and were compared to those measured in the drug-sensitive 8226/S and doxorubicin-resistant 8226/Dox40 cell lines. Both GSH and gamma-GCS activity, the rate-limiting step in the de novo synthesis of GSH, were elevated by a factor of approximately 2 in the melphalan-resistant 8226/LR-5 cells relative to the other two lines. gamma-GT activity was not elevated significantly in the /LR-5 cells. Northern analysis with a probe specific for the large subunit of human liver gamma-GCS identified two bands (3.2 and 4.0 kb), both of which were increased by a factor of 2-3 in the 8226/LR-5 line. Levels of gamma-GCS mRNA expression were comparable in the /S and /Dox40 cell lines. Levels of gamma-GT mRNA were similar in the /S and /LR-5 lines but were reduced in the /Dox40 cells. These data suggest that the increased GSH levels associated with resistance to melphalan in the 8226/LR-5 myeloma cells is attributable to up-regulation of gamma-GCS. This observation is consistent with recent demonstrations of up-regulation of gamma-GCS in melphalan-resistant prostate carcinoma cells and cisplatinum-resistant ovarian carcinoma cells, suggesting that increased expression of gamma-GCS may be an important mediator of GSH-associated resistance mechanisms.

UI MeSH Term Description Entries
D008558 Melphalan An alkylating nitrogen mustard that is used as an antineoplastic in the form of the levo isomer - MELPHALAN, the racemic mixture - MERPHALAN, and the dextro isomer - MEDPHALAN; toxic to bone marrow, but little vesicant action; potential carcinogen. Medphalan,Merphalan,Phenylalanine Mustard,Sarcolysine,Sarkolysin,4-(Bis(2-chloroethyl)amino)phenylalanine,Alkeran,L-PAM,Mustard, Phenylalanine
D009101 Multiple Myeloma A malignancy of mature PLASMA CELLS engaging in monoclonal immunoglobulin production. It is characterized by hyperglobulinemia, excess Bence-Jones proteins (free monoclonal IMMUNOGLOBULIN LIGHT CHAINS) in the urine, skeletal destruction, bone pain, and fractures. Other features include ANEMIA; HYPERCALCEMIA; and RENAL INSUFFICIENCY. Myeloma, Plasma-Cell,Kahler Disease,Myeloma, Multiple,Myeloma-Multiple,Myelomatosis,Plasma Cell Myeloma,Cell Myeloma, Plasma,Cell Myelomas, Plasma,Disease, Kahler,Multiple Myelomas,Myeloma Multiple,Myeloma, Plasma Cell,Myeloma-Multiples,Myelomas, Multiple,Myelomas, Plasma Cell,Myelomas, Plasma-Cell,Myelomatoses,Plasma Cell Myelomas,Plasma-Cell Myeloma,Plasma-Cell Myelomas
D002470 Cell Survival The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability. Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D004317 Doxorubicin Antineoplastic antibiotic obtained from Streptomyces peucetius. It is a hydroxy derivative of DAUNORUBICIN. Adriamycin,Adriablastin,Adriablastine,Adriblastin,Adriblastina,Adriblastine,Adrimedac,DOXO-cell,Doxolem,Doxorubicin Hexal,Doxorubicin Hydrochloride,Doxorubicin NC,Doxorubicina Ferrer Farm,Doxorubicina Funk,Doxorubicina Tedec,Doxorubicine Baxter,Doxotec,Farmiblastina,Myocet,Onkodox,Ribodoxo,Rubex,Urokit Doxo-cell,DOXO cell,Hydrochloride, Doxorubicin,Urokit Doxo cell
D004351 Drug Resistance Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration. Resistance, Drug
D005721 Glutamate-Cysteine Ligase One of the enzymes active in the gamma-glutamyl cycle. It catalyzes the synthesis of gamma-glutamylcysteine from glutamate and cysteine in the presence of ATP with the formation of ADP and orthophosphate. EC 6.3.2.2. gamma-Glutamyl-Cysteine Synthetase,Glutamylcysteine Synthetase,Glutamate Cysteine Ligase,Ligase, Glutamate-Cysteine,Synthetase, Glutamylcysteine,Synthetase, gamma-Glutamyl-Cysteine,gamma Glutamyl Cysteine Synthetase
D005723 gamma-Glutamyltransferase An enzyme, sometimes called GGT, with a key role in the synthesis and degradation of GLUTATHIONE; (GSH, a tripeptide that protects cells from many toxins). It catalyzes the transfer of the gamma-glutamyl moiety to an acceptor amino acid. GGTP,Glutamyl Transpeptidase,gammaglutamyltransferase,gamma-Glutamyl Transpeptidase,Transpeptidase, Glutamyl,Transpeptidase, gamma-Glutamyl,gamma Glutamyl Transpeptidase,gamma Glutamyltransferase
D005978 Glutathione A tripeptide with many roles in cells. It conjugates to drugs to make them more soluble for excretion, is a cofactor for some enzymes, is involved in protein disulfide bond rearrangement and reduces peroxides. Reduced Glutathione,gamma-L-Glu-L-Cys-Gly,gamma-L-Glutamyl-L-Cysteinylglycine,Glutathione, Reduced,gamma L Glu L Cys Gly,gamma L Glutamyl L Cysteinylglycine
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012313 RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed) RNA, Non-Polyadenylated,Ribonucleic Acid,Gene Products, RNA,Non-Polyadenylated RNA,Acid, Ribonucleic,Non Polyadenylated RNA,RNA Gene Products,RNA, Non Polyadenylated

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