Glucocorticoid resistance frequently limits the efficacy of glucocorticoid therapy for human leukemias and lymphomas. The mechanism(s) responsible for this glucocorticoid resistance are poorly understood. The present research concerns the possibility that glucocorticoid receptor defects, similar to those which have been described in mutant mouse lymphoma cell lines, are responsible for glucocorticoid resistance in human leukemias and lymphomas. In preliminary studies, a glucocorticoid receptor defect was found in human leukemia cells which resembles the receptor defect in mutant mouse lymphoma cell lines which have the nuclear transfer increased phenotype of glucocorticoid resistance. The defective receptor is characterized by a decreased molecular weight and is detected by gel electrophoresis of affinity labeled cytosol receptors. The current research proposal will focus upon this receptor defect. First, malignant cells from peripheral blood and bone marrow will be examined in order to determine if the receptor defect is unique to particular types of leukemias or lymphomas and if the presence of the receptor defect correlates with prior glucocorticoid therapy, the number of glucocorticoid receptors per cell, or in vitro glucocorticoid resistance. Second, protease inhibitors will be employed during cytosol preparation to test the role of proteolysis in generating the receptor defect. Third, assays of cytoplasmic-nuclear translocation and DNA-cellulose binding will be employed to determine the functional properties of the defective receptors. Fourth, limited tryptic digestion and domain specific anti-receptor antibodies will be employed to determine the molecular basis for the defective receptors. Fifth, domain specific anti-receptor antibodies will be employed to develop an immunocytochemical assay with which to determine the distribution of the defective receptors within cell populations. This work will result in an improved understanding of the mechanisms by which human leukemia and lymphoma cells become glucocorticoid resistant and will ultimately lead to an assay which can be used to predict which patients are likely to be glucocorticoid resistant during the course of therapy.
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