Therapeutic targeting of EP300/CBP by bromodomain inhibition in hematologic malignancies.

CCS1477 (inobrodib) is a potent, selective EP300/CBP bromodomain inhibitor which induces cell-cycle arrest and differentiation in hematologic malignancy model systems. In myeloid leukemia cells, it promotes rapid eviction of EP300/CBP from an enhancer subset marked by strong MYB occupancy and high H3K27 acetylation, with downregulation of the subordinate oncogenic network and redistribution to sites close to differentiation genes. In myeloma cells, CCS1477 induces eviction of EP300/CBP from FGFR3, the target of the common (4; 14) translocation, with redistribution away from IRF4-occupied sites to TCF3/E2A-occupied sites.

Differentiation block in acute myeloid leukemia regulated by intronic sequences of .

Iroquois transcription factor gene is highly expressed in 20-30% of acute myeloid leukemia (AML) and contributes to the pathognomonic differentiation block. Intron 8 sequences ∼220kB downstream of exhibit histone acetylation, DNA methylation, and contacts with the promoter, which correlate with expression. Deletion of these intronic elements confirms a role in positively regulating .