Abstract
Aberrant gene expression is a hallmark of acute leukemias. MYB-driven transcriptional coactivation with CREB-binding protein (CBP)/P300 is required for acute lymphoblastic and myeloid leukemias, including refractory MLL-rearranged leukemias. Using structure-guided molecular design, we developed a peptidomimetic inhibitor MYBMIM that interferes with the assembly of the molecular MYB:CBP/P300 complex and rapidly accumulates in the nuclei of AML cells. Treatment of AML cells with MYBMIM led to the dissociation of the MYB:CBP/P300 complex in cells, its displacement from oncogenic enhancers enriched for MYB binding sites, and downregulation of MYB-dependent gene expression, including of MYC and BCL2 oncogenes. AML cells underwent mitochondrial apoptosis in response to MYBMIM, which was partially rescued by ectopic expression of BCL2. MYBMIM impeded leukemia growth and extended survival of immunodeficient mice engrafted with primary patient-derived MLL-rearranged leukemia cells. These findings elucidate the dependence of human AML on aberrant transcriptional coactivation, and establish a pharmacologic approach for its therapeutic blockade.
Highlights
Aberrant gene expression is a hallmark of acute leukemias
We designed inactive versions of MYBMIM, termed TG1, TG2, and TG3 (Supplementary Table 1), that are identical to MYBMIM with the exception of substitutions of R294G, L302G, and/or E308G residues that make key contacts with CREB-binding protein (CBP)/P300, as identified from molecular dynamics simulations (Fig. 1a and b, Supplementary Fig. 1)
TG3 showed the lowest affinity to the CBP KIX domain, confirming that it is suitable as an inactive analog of MYBMIM
Summary
Aberrant gene expression is a hallmark of acute leukemias. MYB-driven transcriptional coactivation with CREB-binding protein (CBP)/P300 is required for acute lymphoblastic and myeloid leukemias, including refractory MLL-rearranged leukemias. MYBMIM impeded leukemia growth and extended survival of immunodeficient mice engrafted with primary patient-derived MLL-rearranged leukemia cells These findings elucidate the dependence of human AML on aberrant transcriptional coactivation, and establish a pharmacologic approach for its therapeutic blockade. Chetomin and napthol derivatives have been identified to interfere with the protein–protein interactions of the MYB–CBP/P300 complex[20,21,22] We extended these efforts by focusing on the specific requirement of MYB E308 in its transcriptional activation domain for molecular recognition of the CBP/P300 KIX domain to therapeutically target and dismantle the assembly of the MYB:CBP/P300 leukemogenic transcription factor–coactivator complex, as hypothesized previously[11,23,24]. We investigated its molecular and cellular activities, blockade of leukemogenic gene expression, and therapeutic potential in preclinical leukemia models in vitro and in vivo
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