Sequence-specific transcription factors during glucocorticoid-induced apoptosis in acute lymphoblastic leukemia cells

Glucocorticoids (GC) are known to induce programmed cell death (apoptosis) in certain hematologic malignancies, but the molecular basis of this clinic ally significant phenomenon is poorly understood. GC act via binding to the ir specific receptor, a ligand-activated transcription factor, and might in duce apoptosis by transcriptional activation of "death" or repression of "s urvival" genes. GC regulate gene expression directly, i.e. via GC responsiv e elements, or indirectly by modulating the activity of other transcription factors such as AP-I, NF-KB, Oct, Ets, and CREB. To analyze possible alter ations in the activity of these transcription factors during GC-induced apo ptosis, we performed electrophoretic mobility shift assays using the human acute T-cell leukemia line CCRF-CEM C7H2 as a model system. Although AP-1 w as highly inducible by phorbol ester treatment, it was almost undetectable in logarithmically growing cells and apparently unregulated during GC-induc ed apoptosis. Thus, alterations in AP-1 activity do not appear to be involv ed in GC-induced apoptosis. Oct, Ets, and CREB DNA binding activity were de tectable prior to and during GC treatment, and appeared to have been downre gulated after 48 hours. At this time, however, cells had already undergone considerable apoptosis, and this downregulation might reflect cell death-as sociated protein degradation. In contrast, NF-KB DNA binding activity was r educed 12 to 24 hours after GC exposure but reached levels equal to or high er than pretreatment levels after 48 hours. Thus, while AP-1, Oct, Ets, and CREB may not be involved in GC-induced apoptosis, the maintenance of NF-KB levels suggests that it may participate in this form of cell death.