Glucocorticoid mediated transcriptional repression of c-myc in apoptotic human leukemic CEM cells.

Suppression of c-myc has been implicated as a critical event in some glucocorticoid-evoked apoptotic systems. It is therefore of interest to understand the mechanism of glucocorticoid-regulation of the c-myc gene. In the present study, a detailed analysis of dexamethasone (Dex)-evoked regulation of the human c-myc gene in human leukemic CEM-C7 cells has been performed. Dex suppresses c-myc mRNA and immunoreactive protein expression in clone CEM-C7 and subclone CEM-C7-14 cells. Nuclear run-on assays suggested that the regulation occurred at the level of transcription initiation. The half-life of c-myc mRNA was approximately 30 min and its stability was not affected by Dex treatment. In addition, Dex suppressed luciferase gene expression driven by -2052 to +34 bp c-myc promoter in transfected CEM-C7-14 cells. This result further supports that c-myc gene is suppressed by Dex at the transcriptional level in apoptotic human leukemic cells.