title: Glucocorticoid-receptor-gene defects and resistance to glucocorticoid-induced apoptosis in human leukemic cell lines.
abstract: The application of glucocorticoids (GC3) in human leukemia is based on apoptosis induction but is often hampered by GC resistance. To delineate resistance mechanisms, we examined 5 GC-resistant leukemic cell lines, termed CEM-C7.R1-R5, isolated from the GC-sensitive human acute-T-cell-leukemic line, CCRF-CEM-C7, by selection in GC-containing medium. GC resistance was ascertained by analyzing cell-cycle progression, proliferation, and apoptosis. Radioreceptor assays revealed absence of ligand-binding activity in all clones, suggesting that defects in GC-receptor(GR) expression cause GC resistance. Analyses of the GR gene revealed that all but one (CEM-C7.R5) of the clones were heterozygous for the previously described L753F mutation. CEM-C7.R5 was either hemi- or homozygous for the L753F mutation and, hence, lacked a functional GR. Sequencing of the allele not carrying the L753F mutation of the other GC-resistant sub-lines revealed additional mutations in the GR gene in 3 cases: CEM-C7.R1 and R2 had a base-pair deletion in exon 9 (deltaT740) that resulted in a reading-frame shift and a pre-terminal in-frame stop. Translation of this mutant mRNA would produce a protein lacking 32 amino acids and expressing 4 altered residues at its new C terminus. CEM-C7.R3 harbored a non-sense mutation (Q710X) in exon 8, and its mRNA would be translated into a protein lacking 67 residues. Only CEM-C7.R4 cells were devoid of mutations in the coding region of the L753F negative allele. These data suggest that, in the CCRF-CEM acute-lymphatic-leukemia model, mutations in the GR-gene coding region represent one, but not the only, cause of GC resistance.
authors.affiliation: Institute for General and Experimental Pathology, Division of Molecular Pathophysiology, University of Innsbruck, School of Medicine, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Hala
authors.forename: B L
authors.initials: BL
authors.lastname: Hartmann
authors.forename: G
authors.initials: G
authors.lastname: Böck
authors.forename: S
authors.initials: S
authors.lastname: Geley
authors.forename: R
authors.initials: R
authors.lastname: Kofler
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D005938:Glucocorticoids / Q000008:administration & dosage*; D006801:Humans; D007938:Leukemia / Q000235:genetics* / Q000473:pathology; D008969:Molecular Sequence Data; D009154:Mutation; D011965:Receptors, Glucocorticoid / Q000235:genetics*; D014407:Tumor Cells, Cultured
chemical_list: D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid