A synthetic covalent ligand of the C/EBPβ transactivation domain inhibits acute myeloid leukemia cells

C/EBPβ has recently emerged as a pro-leukemogenic transcription factor that cooperates with oncoprotein MYB to maintain proliferation and differentiation block of AML cells, making C/EBPβ an interesting drug target for AML. Here we have studied the inhibitory potential and biological effects of a synthetic analog of the natural product helenalin, a known inhibitor of C/EBPβ. The synthetic compound inhibits C/EBPβ by covalent binding to cysteine residues in the transactivation domain, thereby causing up-regulation of differentiation-associated genes, cell death and reduced self-renewal potential of AML cells. Suppression of these effects by ectopic expression of C/EBPβ or MYB and gene expression profiling validate C/EBPβ as a relevant target of the helenalin-mimic and highlight its role as a pro-leukemogenic factor. Overall, our work demonstrates that the synthetic helenalin mimic acts as a covalent inhibitor of C/EBPβ and identifies the cysteine residues in the transactivation domain of C/EBPβ as ligandable sites. The helenalin mimic can be considered a potential "lead molecule" but needs further development towards more effective C/EBPβ inhibitors before being used as a therapeutic agent.