C/EBPγ deregulation results in differentiation arrest in acute myeloid leukemia.

C/EBPs are a family of transcription factors that regulate growth control and differentiation of various tissues. We found that C/EBPγ is highly upregulated in a subset of acute myeloid leukemia (AML) samples characterized by C/EBPα hypermethylation/silencing. Similarly, C/EBPγ was upregulated in murine hematopoietic stem/progenitor cells lacking C/EBPα, as C/EBPα mediates C/EBPγ suppression. Studies in myeloid cells demonstrated that CEBPG overexpression blocked neutrophilic differentiation. Further, downregulation of Cebpg in murine Cebpa-deficient stem/progenitor cells or in human CEBPA-silenced AML samples restored granulocytic differentiation. In addition, treatment of these leukemias with demethylating agents restored the C/EBPα-C/EBPγ balance and upregulated the expression of myeloid differentiation markers. Our results indicate that C/EBPγ mediates the myeloid differentiation arrest induced by C/EBPα deficiency and that targeting the C/EBPα-C/EBPγ axis rescues neutrophilic differentiation in this unique subset of AMLs.