title: Severe depletion of cellular thiols and glutathione-related enzymes of a carmustine-resistant L1210 strain associates with collateral sensitivity to cyclophosphamide.
abstract: Cyclophosphamide (CPA) increased the life span of both carmustine (BCNU)-resistant (L1210/BCNU) and BCNU-sensitive L1210 (L1210/0) leukaemic mice; their sensitivity to CPA, however, was extremely different. The BCNU-resistant strain was much more sensitive (collaterally) to CPA than was its sensitive counterpart. The collateral sensitivity was accompanied by a severe reduction in the activity of glutathione-related enzymes and in protein thiol (SH) and non-protein SH levels in BCNU-resistant cells. The activity of glutathione reductase (GSSG-R) was 2 times higher in the L1210/0 cells than in the L1210/BCNU cells. Glutathione-S-transferase (GST) was also almost 2 times more active in the sensitive cells than in the resistant strain. To develop resistance against CPA with a single treatment (60 mg/kg) per passage, the L1210/BCNU strain needed 26 passages, whereas the L1210/0 strain required significantly fewer. The resistance developed against CPA was associated with a moderate elevation of thiols in the L1210/CPA cells, whereas this elevation was approximately 3 times more pronounced in the L1210/BCNU/CPA cells. The severely reduced activity of GST in the L1210/BCNU strain was markedly increased when these cells were made resistant to CPA; the GSSG-R activity, however, remained low, suggesting an irreversible injury of this enzyme by BCNU.
authors.affiliation: National Institute of Oncology, Budapest, Hungary.
authors.forename: E
authors.initials: E
authors.lastname: Institoris
authors.forename: L
authors.initials: L
authors.lastname: Tretter
authors.forename: D
authors.initials: D
authors.lastname: Gaál
mesh_terms: D000818:Animals; D002330:Carmustine / Q000494:pharmacology*; D003520:Cyclophosphamide / Q000494:pharmacology*; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D005980:Glutathione Reductase / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism*; D007939:Leukemia L1210 / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008815:Mice, Inbred Strains; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism
chemical_list: D013438:Sulfhydryl Compounds; D003520:Cyclophosphamide; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D002330:Carmustine