CEBPA-mutated leukemia is sensitive to genetic and pharmacological targeting of the MLL1 complex

Abstract

The gene encoding the transcription factor C/EBPα is mutated in 10-15% of acute myeloid leukemia (AML) patients. N-terminal CEBPA mutations cause ablation of full-length C/EBPα without affecting the expression of a shorter oncogenic isoform, termed p30. The mechanistic basis of p30-induced leukemogenesis is incompletely understood. Here, we demonstrate that the MLL1 histone-methyltransferase complex represents a critical actionable vulnerability in CEBPA -mutated AML. Oncogenic C/EBPα p30 and MLL1 show global co-localization on chromatin and p30 exhibits robust physical interaction with the MLL1 complex. CRISPR/Cas9-mediated mutagenesis of MLL1 results in proliferation arrest and myeloid differentiation in C/EBPα p30-expressing cells. In line, CEBPA -mutated hematopoietic progenitor cells are hypersensitive to pharmacological targeting of the MLL1 complex. Inhibitor treatment impairs proliferation and restores myeloid differentiation potential in mouse and human AML cells with CEBPA mutations. Finally, we identify the transcription factor GATA2 as a direct critical target of the p30-MLL1 interaction. Altogether, we show that C/EBPα p30 requires the MLL1 complex to regulate oncogenic gene expression and that CEBPA -mutated AML is hypersensitive to perturbation of the MLL1 complex. These findings identify the MLL1 complex as a potential therapeutic target in AML with CEBPA mutations.

Gain‐of‐Function Effects of N‐Terminal CEBPA Mutations in Acute Myeloid Leukemia

“…The C/EBPα p30 variant can also exert specific functions through its interaction with epigenetic regulators. Affinity purification followed by mass spectrometry and co‐immunoprecipitation studies found that the p30 isoform preferentially interacted with the MLL1 methyltransferase complex, which catalyzes H3K4 tri‐methylation . Consistently, there was a large overlap in global chromatin association of C/EBPα p30 and the MLL1 complex.…”

“…Affinity purification followed by mass spectrometry and co-immunoprecipitation studies found that the p30 isoform preferentially interacted with the MLL1 methyltransferase complex, which catalyzes H3K4 trimethylation. [ 46 , 47 ] Consistently, there was a large overlap in global chromatin association of C/EBP α p30 and the MLL1 complex. These data indicate a cooperation of p30 with the MLL1 methyltransferase complex in the regulation of genes that are critical for the oncogenic effect of p30.…”

“…These data indicate a cooperation of p30 with the MLL1 methyltransferase complex in the regulation of genes that are critical for the oncogenic effect of p30. CRISPR/Cas9‐mediated mutagenesis revealed that p30‐expressing cells are dependent on a functional MLL1 protein . Disruption of the MLL1 complex function by small‐molecule‐mediated inhibition of the MLL1‐Menin or MLL1‐WDR5 interaction resulted in impaired proliferation, induction of differentiation, and elevated levels of apoptosis of CEBPA ‐mutated cells …”

“…CRISPR/Cas9-mediated mutagenesis revealed that p30-expressing cells are dependent on a functional MLL1 protein. [ 47 ] Disruption of the MLL1 complex function by small-molecule-mediated inhibition of the MLL1-Menin or MLL1-WDR5 interaction resulted in impaired proliferation, induction of differentiation, and elevated levels of apoptosis of CEBPA -mutated cells. [ 46 , 47 ]…”

Pediatric Acute Myeloid Leukemia (AML): From Genes to Models Toward Targeted Therapeutic Intervention

“…In addition to MENIN/LEDGF or DOT1L, targeted interference with other components of the KMT2A fusion complexes (e.g., WDR5, BRD4, CDK9) have been explored in various preclinical models (125). Interestingly, AML cells carrying CEBPA mutations leading to expression of the short oncogenic CEBP/α p30 isoform appear sensitive to pharmacological targeting of the KMT2A complex (126). However, so far, no strategy has been reported that allows selective degradation of KMT2A fusion proteins to replicate the success in APL.…”