Glucocorticoid-receptor-gene defects and resistance to glucocorticoid-induced apoptosis in human leukemic cell lines

✍ Scribed by Monika Hala; Bernd L. Hartmann; Günther Böck; Stephen Geley; Reinhard Kofler

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: French
• Weight: 674 KB
• Volume: 68
• Category: Article
• ISSN: 0020-7136
• DOI: 10.1002/(sici)1097-0215(19961127)68:5<663::aid-ijc17>3.0.co;2-2

✦ Synopsis

The application of glucocorticoids (GC') 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.RI-R5, isolated from the GC-sensitive human acute-1-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-CI.W) of the clones were heterozygous for the previously described L753F mutation. CEM-C7.R5 was either hemior homozygous for the L753F mutation and, hence, lacked a functional G R 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.RI and R2 had a base-pair deletion in exon 9 (Al740) 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 (Q7IOX) 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.