The long-term goal of this ongoing grant is understanding how the glucocorticoid receptor (GR) regulates genes to effect the death of leukemic lymphoid cells. Our findings have laid the groundwork for research in our next grant period. Glucocorticoids, through activation of the GR, have identified several landmark genes whose regulation by glucocorticoids precedes the onset of overt apoptosis. Of high significance is the observation that transcriptional repression of c-myc is invariably seen in cells sensitive to glucocorticoid (or rendered sensitive by activation of protein kinase A). We have begun gene array analysis to reveal all such genes antecedent to the eventual apoptotic events. We have developed a well-controlled set of clonal cell lines from the human acute lymphoblastic leukemia CEM cell line. Comparing the genes expressed in these clones will allow us to identify the genes whose regulation is specifically relevant to apoptotic onset. Our recent discovery of two pharmacological interventions that enhance glucocorticoid-evoked apoptosis should allow further refinement of this gene set. Based on these findings, in the next grant period our research will center on four specific aims. We will: 1) define by gene array analysis those genes whose altered expression is required for glucocorticoid-evoked CEM cell death; 2) test the hypothetical causal relationships between such genes; 3) obtain protein expression profiles unique to glucocorticoid-sensitive cells; and 4) test the role of the major, N-terminal transcription-activating domain of the GR in the above regulatory events. To carry out these experiments, we will combine expertise in molecular and cell biology, genomics, proteomics and bioinformatics. The resulting data will test the hypothesis that a network of interactive gene products is responsible for the glucocorticoid-evoked apoptosis. If our hypothesis is correct, this work will lead to the discovery of that network in a leukemic cell system, providing the foundation for detailed comparisons with other lymphoid systems, normal and malignant. This would open the way for studies of novel interventions against malignancies.
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