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Glucocorticoid receptors and glucocorticoid sensitivity of human leukemic cells
Abstract:
We have established optimal conditions for the measurement of glucocorticoid receptors (GR) in human white cells using a whole-cell binding assay with [3H]dexamethasone as the ligand, and the subsequent determination of the GR content in normal human lymphocytes and in leukemic cells of patients with various forms of acute and chronic leukemia. A number of leukemia cell lines in continuous culture were also subjected to the GR assay, and the results were correlated with the sensitivity of these cell lines to glucocorticoid steroids in vitro. The GR content of normal human lymphocytes amounted to 4,850 +/- 1,340 (mean +/- SD) receptors/cell. The mean equilibrium dissociation constant (KD) of the interaction of [3H]dexamethasone with the GR was 1.2 x 10(-8) M. Steroidal compounds with a known glucocorticoid potency effectively competed for the binding, whereas steroids devoid of glucocorticoid activity (e.g. estradiol-17 beta and testosterone) were ineffective. The GR content of the blast cells obtained from eight patients suffering from acute leukemia and four patients with a blast crisis of chronic myelocytic leukemia was found to be highly variable (3,230-29,900 receptors/cell), while the lymphocytes of six patients with chronic lymphatic leukemia contained a rather stable GR content (2,930-5,120 receptors/cell), which was comparable with that of normal lymphocytes. GR was identified in all the 12 malignant continuous white cell lines studied. Large cells contained more GR than the smaller ones. There was no apparent correlation between the GR concentration and the sensitivity of the cells in vitro to glucocorticoids as judged by [3H]thymidine incorporation studies. Distribution of the surface markers in the leukemic cell lines did not relate to the GR concentration. We conclude that the presence of GR is probably a universal feature of the leukemic cells, and, from a clinical standpoint, probably does not alone imply steroid responsiveness.