Project description:The chromatin adaptor protein Menin (MEN1) is required by acute leukemias driven by mixed lineage leukemia 1 gene rearrangements (KMT2A-r) for sustained leukemogenesis. Menin inhibitors (MIs), which disrupt the Menin-KMT2A interface leading to downregulation of Menin-KMT2A oncogenic transcriptional programs, have shown promising results in recent clinical trials treating acute myeloid leukemia (AML). Decreased Menin protein stability has been observed following treatment with several MIs though proteasomal degradation, though the biological mechanisms that control Menin stability are not well understood. Here we interrogate and compare five clinical MIs and two pre-clinical compounds to characterize the mechanism by which MIs induce Menin degradation and demonstrate that the loss of the Menin-KMT2A interaction results in decreased protein stability of Menin and KMT2A. We have identified the HECT E3 ubiquitin ligase UBR5 as a regulator of Menin protein stability and demonstrate that UBR5 binds to similar sites as the Menin/KMT2A complex on chromatin. Loss of UBR5 leads to transcriptional rescue of Menin-KMT2A target genes leading to decreased sensitivity to all MIs. Thus, we present UBR5 as an important regulator of Menin/KMT2A complex stability and Menin destabilization/subcellular localization as a designable feature of Menin inhibition targeting KMT2A-r leukemias.
Project description:The chromatin adaptor protein Menin (MEN1) is required by acute leukemias driven by mixed lineage leukemia 1 gene rearrangements (KMT2A-r) for sustained leukemogenesis. Menin inhibitors (MIs), which disrupt the Menin-KMT2A interface leading to downregulation of Menin-KMT2A oncogenic transcriptional programs, have shown promising results in recent clinical trials treating acute myeloid leukemia (AML). Decreased Menin protein stability has been observed following treatment with several MIs though proteasomal degradation, though the biological mechanisms that control Menin stability are not well understood. Here we interrogate and compare five clinical MIs and two pre-clinical compounds to characterize the mechanism by which MIs induce Menin degradation and demonstrate that the loss of the Menin-KMT2A interaction results in decreased protein stability of Menin and KMT2A. We have identified the HECT E3 ubiquitin ligase UBR5 as a regulator of Menin protein stability and demonstrate that UBR5 binds to similar sites as the Menin/KMT2A complex on chromatin. Loss of UBR5 leads to transcriptional rescue of Menin-KMT2A target genes leading to decreased sensitivity to all MIs. Thus, we present UBR5 as an important regulator of Menin/KMT2A complex stability and Menin destabilization/subcellular localization as a designable feature of Menin inhibition targeting KMT2A-r leukemias.
Project description:Precise control of activating H3K4me3 and repressive H3K27me3 histone modifications at bivalent promoters is essential for normal development and is frequently corrupted in cancer. By coupling a cell surface readout of bivalent MHC class I gene expression with whole genome CRISPR/Cas9 screens, we identify specific roles for MTF2-PRC2.1, PCGF1-PRC1.1 and Menin- KMT2A/B complexes in maintaining bivalency. Unexpectedly, genetic loss or pharmacological inhibition of Menin phenocopies the effects of polycomb disruption, resulting in derepression of bivalent genes in both cancer cells and pluripotent stem cells. Whilst Menin and KMT2A/B contribute to H3K4me3 at active genes, a separate Menin-independent function of KMT2A/B maintains H3K4me3 and opposes polycomb-mediated repression at bivalent genes. Release of KMT2A from active genes following Menin targeting alters the balance of polycomb and KMT2A at bivalent genes, facilitating gene activation. This functional partitioning of Menin-KMT2A/B complex components reveals novel therapeutic opportunities that can be leveraged through inhibition of Menin.
Project description:Targeting critical epigenetic regulators reverses aberrant transcription in cancer, thereby restoring normal tissue function. The interaction of menin with lysine methyltransferase 2A (KMT2A), an epigenetic regulator, is a dependency in acute leukaemia caused by either rearrangement of KMT2A or mutation in Nucleophosmin 1(NPM1). KMT2A rearrangements occur in up to 10% of acute leukaemias and have an adverse prognosis whereas NPM1 mutations occur in up to 30%, forming the most common genetic alteration in acute myeloid leukaemia7,8. Here, we describe the results of the first-in-human phase 1 clinical trial investigating revumenib (SNDX-5613), a potent and selective oral inhibitor of the menin–KMT2A interaction, in patients with relapsed or refractory acute leukaemia (ClinicalTrials.gov, NCT04065399). We show that therapy with revumenib was associated with a low frequency of grade 3 or higher treatment-related adverse events and a 30% rate of complete remission or complete remission with partial haematologic recovery (CR/CRh) in the efficacy analysis population. Asymptomatic prolongation of the QT interval on electrocardiography was identified as the only dose-limiting toxicity. Remissions occurred in leukaemias refractory to multiple previous lines of therapy. We demonstrate clearance of residual disease using sensitive clinical assays and identify hallmarks of differentiation into normal haematopoietic cells, including differentiation syndrome. These data establish menin inhibition as a therapeutic strategy for susceptible acute leukaemia subtypes.
Project description:Pharmacologic targeting of epigenetic protein complexes has shown significant in vitro responses in acute myeloid leukemia (AML). Early clinical trials in KMT2A-rearranged leukemia indicate rather transient responses and development of resistance. In an effort to define functional dependencies of KMT2A-fusions in AML, we identify the catalytic immunoproteasome subunit PSMB8 as a KMT2A-complex-specific vulnerability. Genetic and pharmacologic inactivation of PSMB8 results in impaired proliferation of murine and human leukemic cells while normal hematopoietic cells remain unaffected. Disruption of immunoproteasome function results in cellular enrichment of transcription factor BASP1, and consecutive repression of KMT2A-target genes. Pharmacologic targeting of PSMB8 improves efficacy of Menin-inhibitors, eradicates leukemia in primary human xenografts and shows preserved activity against Menin-inhibitor resistance mutations. This identifies and validates a cell-intrinsic mechanism whereby selective disruption of proteostasis results in altered transcription factor abundance and repression of oncogene-specific transcriptional networks. Therapeutic targeting of PSMB8-dependent transcription in combination with Menin-inhibition could thus eradicate KMT2A-complex driven AML.
Project description:Menin inhibitors that disrupt Menin-MLL interaction hold promise for treating specific acute myeloid leukemia subtypes, including KMT2A rearrangements (KMT2A-r), yet resistance remains a challenge. Here, through systematic chromatin-focused CRISPR screens, along with genetic, epigenetic, and pharmacologic studies in a variety of human and mouse KMT2A-r AML models, we uncover a potential resistance mechanism independent of canonical Menin-MLL targets. We show that a group of non-canonical Menin targets, which are bivalently co-occupied by active Menin and repressive H2AK119ub marks, are typically downregulated following Menin inhibition. The loss of Polycomb Repressive Complex 1.1 (PRC1.1) subunits, such as PCGF1 or BCOR, leads to Menin inhibitor resistance by epigenetic reactivation of these non-canonical targets, including MYC. Genetic and pharmacological inhibition of MYC can resensitize PRC1.1-deficent leukemia cells to Menin inhibition. Moreover, we demonstrate that leukemia cells with the loss of PRC1.1 subunits exhibit reduced monocytic gene signatures and are susceptible to the BCL2 inhibition, and combinational treatment of venetoclax overcomes the resistance to Menin inhibition in PRC1.1-deficient leukemia cells. These findings highlight the important roles of PRC1.1 and its regulated non-canonical Menin targets in modulating Menin inhibitor response and provide potential strategies to treat leukemias with compromised PRC1.1 function.
Project description:Menin inhibitors that disrupt Menin-MLL interaction hold promise for treating specific acute myeloid leukemia subtypes, including KMT2A rearrangements (KMT2A-r), yet resistance remains a challenge. Here, through systematic chromatin-focused CRISPR screens, along with genetic, epigenetic, and pharmacologic studies in a variety of human and mouse KMT2A-r AML models, we uncover a potential resistance mechanism independent of canonical Menin-MLL targets. We show that a group of non-canonical Menin targets, which are bivalently co-occupied by active Menin and repressive H2AK119ub marks, are typically downregulated following Menin inhibition. The loss of Polycomb Repressive Complex 1.1 (PRC1.1) subunits, such as PCGF1 or BCOR, leads to Menin inhibitor resistance by epigenetic reactivation of these non-canonical targets, including MYC. Genetic and pharmacological inhibition of MYC can resensitize PRC1.1-deficent leukemia cells to Menin inhibition. Moreover, we demonstrate that leukemia cells with the loss of PRC1.1 subunits exhibit reduced monocytic gene signatures and are susceptible to the BCL2 inhibition, and combinational treatment of venetoclax overcomes the resistance to Menin inhibition in PRC1.1-deficient leukemia cells. These findings highlight the important roles of PRC1.1 and its regulated non-canonical Menin targets in modulating Menin inhibitor response and provide potential strategies to treat leukemias with compromised PRC1.1 function.
Project description:To investigate the effect of Menin inhibitor on UBTF-TD harboring AML. We characterized UBTF-TD interaction with KMT2A and Menin in different leukemia models including KMT2A-r, transduced and normal cbCD34+ cells as well as in primary AML cells with UBTF-TD mutation. We also analized gene expression pattern upon treatment with Menin inhibitor.
Project description:Small molecules that target the MENIN-KMT2A protein-protein interaction (Menin inhibitors) have recently entered clinical trials in lysine methyltransferase 2A (KMT2A, MLL1) rearranged (KMT2A-r) and nucleophosmin mutant (NPM1c) acute myeloid leukemia (AML) and are demonstrating encouraging results. However, rationally chosen combination therapy is needed to improve responses and prevent resistance. We have previously identified IKZF1/IKAROS as a target in KMT2A-r AML and shown in preclinical models that IKAROS protein degradation with Lenalidomide or Iberdomide has modest single-agent activity yet can synergize with Menin inhibitors. Recently, the novel IKAROS degrader Mezigdomide was developed and has greatly enhanced IKAROS protein degradation. In this study we show that Mezigdomide has increased preclinical activity in vitro as a single-agent in KMT2A-r and NPM1c AML cell lines, including sensitivity in cell lines resistant to Lenalidomide and Iberdomide. Further, we demonstrate that Mezigdomide has the greatest capacity to synergize with and induce apoptosis in combination with Menin inhibitors. We show that the superior activity of Mezigdomide compared to Lenalidomide or Iberdomide is due to its increased depth, rate, and duration of IKAROS protein degradation. Single-agent Mezigdomide was efficacious in five patient derived xenograft (PDX) models of KMT2A-r and one NPM1c AML. The combination of Mezigdomide with a Menin inhibitor increased survival and prevented the development of recently described MEN1 mutations. These results support prioritization of Mezigdomide for early phase clinical trials in KMT2A-r and NPM1c AML, either as a single-agent or in combination with Menin inhibitors.