RESUMO
C/EBPß 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/EBPß 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/EBPß. The synthetic compound inhibits C/EBPß 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/EBPß or MYB and gene expression profiling validate C/EBPß 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/EBPß and identifies the cysteine residues in the transactivation domain of C/EBPß as ligandable sites. The helenalin mimic can be considered a potential "lead molecule" but needs further development towards more effective C/EBPß inhibitors before being used as a therapeutic agent.
Assuntos
Proteína beta Intensificadora de Ligação a CCAAT/genética , Leucemia Mieloide Aguda/tratamento farmacológico , Sesquiterpenos de Guaiano/farmacologia , Ativação Transcricional/efeitos dos fármacos , Células 3T3 , Animais , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Linhagem Celular , Linhagem Celular Tumoral , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Células HEK293 , Células HL-60 , Humanos , Leucemia Mieloide Aguda/genética , Ligantes , Camundongos , Camundongos Endogâmicos C57BL , Regiões Promotoras Genéticas/efeitos dos fármacos , Regiões Promotoras Genéticas/genética , Células THP-1RESUMO
Transcription factor MYB has recently emerged as a promising drug target for the treatment of acute myeloid leukemia (AML). Here, we have characterized a group of natural sesquiterpene lactones (STLs), previously shown to suppress MYB activity, for their potential to decrease AML cell proliferation. Unlike what was initially thought, these compounds inhibit MYB indirectly via its cooperation partner C/EBPß. C/EBPß-inhibitory STLs affect the expression of a large number of MYB-regulated genes, suggesting that the cooperation of MYB and C/EBPß broadly shapes the transcriptional program of AML cells. We show that expression of GFI1, a direct MYB target gene, is controlled cooperatively by MYB, C/EBPß, and co-activator p300, and is down-regulated by C/EBPß-inhibitory STLs, exemplifying that they target the activity of composite MYB-C/EBPß-p300 transcriptional modules. Ectopic expression of GFI1, a zinc-finger protein that is required for the maintenance of hematopoietic stem and progenitor cells, partially abrogated STL-induced myelomonocytic differentiation, implicating GFI1 as a relevant target of C/EBPß-inhibitory STLs. Overall, our data identify C/EBPß as a pro-leukemogenic factor in AML and suggest that targeting of C/EBPß may have therapeutic potential against AML.