Glucocorticoid receptor gene mutations in leukemic cells acquired in vitroand in vivo

Glucocorticoid resistance was investigated in human leukemic: CCRF-CEM cell s. A mutation (L753F), which renders the human glucocorticoid receptor (hGR ) gene functionally hemizygous, was identified in all CEM-derived cell line s analyzed, Allele-specific PCR identified the same mutation in lymph node biopsy material from patient CEM cells. Given the correlation between hGR c oncentration and glucocorticoid sensitivity, this suggests that loss of fun ctional heterozygosity may result in resistance to glucocorticoid-based che motherapy, The L753F mutation was probably not responsible for the ontogeny of the disease because it did not appear to be present in all leukemic cel ls. Thus, it is unlikely that hGR mutations would be detected in leukemic p atients at presentation, but they may occur, and be selected for, during tr eatment. Deletions and point mutations in the hGR gene of cells selected fo r steroid resistance in vitro were investigated by PCR-single strand confor mation polymorphism analysis. Loss of hGR mRNA expression resulted from 5'- deletion of the hGR gene and nonsense mutations in exon 6, These results pr ovide the first evidence for somatic mutation in the hGR gene of a patient with acute lymphoblastic leukemia, offer a potential in vivo mechanism for acquisition of steroid resistance in leukemia, and suggest that screening f or additional in vivo mutations will require analysis of genomic DNA.