Glucocorticoid resistance in two key models of acute lymphoblastic leukemia occurs at the level of the glucocorticoid receptor

Schmidt,S.; Irving,J.A.; Minto,L.; Matheson,E.; Nicholson,L.; Ploner,A.; Parson,W.; Kofler,A.; Amort,M.; Erdel,M.; Hall,A.; Kofler,R.
Glucocorticoids (GCs) specifically induce apoptosis in malignant lymphoblasts and are thus pivotal in the treatment of acute lymphoblastic leukemia (ALL). However, GC-resistance is a therapeutic problem with an unclear molecular mechanism. We generated approximately 70 GC-resistant sublines from a GC-sensitive B- and a T-ALL cell line and investigated their mechanisms of resistance. In response to GCs, all GC-resistant subclones analyzed by real-time polymerase chain reaction (PCR) showed a deficient up-regulation of the GC-receptor (GR) and its downstream target, GC-induced leucine zipper. This deficiency in GR up-regulation was confirmed by Western blotting and on retroviral overexpression of GR in resistant subclones GC-sensitivity was restored. All GC-resistant subclones were screened for GR mutations using denaturing high-pressure liquid chromatography (DHPLC), DNA-fingerprinting, and fluorescence in situ hybridization (FISH). Among the identified mutations were some previously not associated with GC resistance: A484D, P515H, L756N, Y663H, L680P, and R714W. This approach revealed three genotypes, complete loss of functional GR in the mismatch repair deficient T-ALL model, apparently normal GR genes in B-ALLs, and heterozygosity in both. In the first genotype, deficiency in GR up-regulation was fully explained by mutational events, in the second by a putative regulatory defect, and in the third by a combination thereof. In all instances, GC-resistance occurred at the level of the GR in both models
FASEB J 2006 20(14):2600-2602
Tags: Apoptosis; Austria; Cell Line,Tumor; DNA Fingerprinting; DNA Mismatch Repair; Drug Resistance,Neoplasm; drug therapy; FLUORESCENCE; GENE; genetics; genotype; Glucocorticoids; human; In Situ Hybridization; Leukemia,Lymphocytic,Acute; liquid chromatography; metabolism; Mutation; MUTATIONS; PCR; polamerase; polamerase-CHAIN-REACTION; polymerase chain reaction; Protein; Receptors,Glucocorticoid; RESISTANCE; therapeutic use; Transcription Factors
PubMed: 17077285
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