title: Dexamethasone-resistant human Pre-B leukemia 697 cell line evolving elevation of intracellular glutathione level: an additional resistance mechanism.
abstract: Glucocorticoids remain among the most important drugs in the treatment of acute lymphoblastic leukemia (ALL). Although the mechanisms of glucocorticoid resistance have been studied in some T-cell leukemic cell lines, less work has been done with B-cell lines. We established a dexamethasone (DEX)-resistant human pre-B lineage leukemia cell line (697/DEX) and investigated the mechanism of resistance. 697/DEX was over 430-fold more resistant to DEX compared with the parental cells (697/Neo). Overexpression of Bcl-2 protein was not observed in 697/DEX, different from the mechanism of resistance in Bcl-2-virus-infected cells (697/Bcl-2). Although the expression of p-glycoprotein (Pgp) in 697/DEX was positive, its functional activity was not detected. The numbers of glucocorticoid receptors (GR) in 697/DEX and 697/Bcl-2 were significantly lower than those in 697/Neo. In addition, 697/DEX and 697/Bcl-2 had higher levels of glutathione (GSH) than 697/Neo. In the presence of L-buthionine-(S, R)-sulfoximine (BSO), an inhibitor of GSH synthesis, both 697/DEX and 697/Bcl-2 recovered their sensitivity to DEX. Interestingly, cell death by the depletion of GSH did not involve caspase-3/7 activation in 697/Bcl-2 and 697/DEX, different from 697/Neo, suggesting a death mechanism through caspase-independent programmed cell death or necrosis. In conclusion, DEX-resistance in 697/DEX was related not only to a GR decrease, but also to an increase in intracellular GSH level in the DEX-resistant B-cell leukemia cell line. Circumvention of DEX-resistance with BSO may offer an approach to overcoming resistance to chemotherapy in B-cell lineage ALL.
authors.affiliation: First Department of Internal Medicine, Fukui Medical University, Matsuoka-cho, Yoshida-gun, Fukui 910-1193.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Inoue
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Takemura
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Kawai
authors.forename: Akira
authors.initials: A
authors.lastname: Yoshida
authors.forename: Takanori
authors.initials: T
authors.lastname: Ueda
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Miyashita
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism / Q000473:pathology*; D011379:Prognosis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000964:Antimetabolites, Antineoplastic; D018931:Antineoplastic Agents, Hormonal; D019253:Proto-Oncogene Proteins c-bcl-2; D011965:Receptors, Glucocorticoid; D019328:Buthionine Sulfoximine; D003907:Dexamethasone; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases; D005978:Glutathione