Glucocorticoid binding proteins in human leukaemic lymphoblasts

Steroid binding activity (SBP) in glucocorticoid sensitive and resistant lymphoblasts was measured by a competitive binding assay in which cytosol was incubated at 0°C in the presence of various concentrations of ³H dexamethasone in the presence or absence of an excess of unlabeled dexamethasone, modified by performing the reaction for 2 hr in buffer which had been made 20% with respect to glycerol. The authors have demonstrated a class of highly specific, saturable, glucocorticoid receptor molecules in cytosol preparations, obtained from glucocorticoid sensitive human ALL cells. There is a positive correlation between steroid responsiveness of lymphoblasts and the presence of this SBP and a lack of glucocorticoid responsiveness in its absence. An in vitro test of steroid responsiveness might help leukemia treatment both by identifying those patients likely to benefit from steroid therapy and eliminating use of glucocorticoids when leukemic cells are no longer inhibited by steroids, thus avoiding unnecessary drug toxicity.