Dimeric peroxiredoxins are druggable targets in human Burkitt lymphoma

Burkitt lymphoma is a fast-growing tumor derived from germinal center B cells. It is mainly treated with aggressive chemotherapy, therefore novel therapeutic approaches are needed due to treatment toxicity and developing resistance. Disturbance of red-ox homeostasis has recently emerged as an efficient antitumor strategy. Peroxiredoxins (PRDXs) are thioredoxin-family antioxidant enzymes that scavenge cellular peroxides and contribute to red-ox homeostasis. PRDXs are robustly expressed in various malignancies and critically involved in cell proliferation, differentiation and apoptosis. To elucidate potential role of PRDXs in lymphoma, we studied their expression level in B cell-derived primary lymphoma cells as well as in cell lines. We found that PRDX1 and PRDX2 are upregulated in tumor B cells as compared with normal counterparts. Concomitant knockdown of PRDX1 and PRDX2 significantly attenuated the growth rate of lymphoma cells. Furthermore, in human Burkitt lymphoma cell lines, we isolated dimeric 2-cysteine peroxiredoxins as targets for SK053, a novel thiol-specific small-molecule peptidomimetic with antitumor activity. We observed that treatment of lymphoma cells with SK053 triggers formation of covalent PRDX dimers, accumulation of intracellular reactive oxygen species, phosphorylation of ERK1/2 and AKT and leads to cell cycle arrest and apoptosis. Based on site-directed mutagenesis and modeling studies, we propose a mechanism of SK053-mediated PRDX crosslinking, involving double thioalkylation of active site cysteine residues. Altogether, our results suggest that peroxiredoxins are novel therapeutic targets in Burkitt lymphoma and provide the basis for new approaches to the treatment of this disease

Discovery of first-in-class inhibitors of ASH1L histone methyltransferase with anti-leukemic activity

ASH1L histone methyltransferase plays a crucial role in the pathogenesis of different diseases, including acute leukemia. While ASH1L represents an attractive drug target, developing ASH1L inhibitors is challenging, as the catalytic SET domain adapts an inactive conformation with autoinhibitory loop blocking the access to the active site. Here, by applying fragment-based screening followed by medicinal chemistry and a structure-based design, we developed first-in-class small molecule inhibitors of the ASH1L SET domain. The crystal structures of ASH1L-inhibitor complexes reveal compound binding to the autoinhibitory loop region in the SET domain. When tested in MLL leukemia models, our lead compound, AS-99, blocks cell proliferation, induces apoptosis and differentiation, downregulates MLL fusion target genes, and reduces the leukemia burden in vivo. This work validates the ASH1L SET domain as a druggable target and provides a chemical probe to further study the biological functions of ASH1L as well as to develop therapeutic agents

Synthesis of novel, peptidic kinase inhibitors with cytostatic/cytotoxic activity

The utility of a novel, chemoenzymatic procedure for the stereocontrolled synthesis of small peptides is presented in the preparation and structure optimisation of dipeptides with cytostatic/cytotoxic activity. The method uses Passerini multicomponent reaction for the preparation of racemic scaffold which is then enantioselectively hydrolysed by hydrolytic enzymes. Products of these transformations are further functionalised towards title compounds. Both activity and selectivity towards tumor cells is optimised. Final compound is shown to be an inhibitor of the protein kinase signaling pathway. (C) 2014 Elsevier Ltd. All rights reserved

Complexity of Blocking Bivalent Protein–Protein Interactions: Development of a Highly Potent Inhibitor of the Menin–Mixed-Lineage Leukemia Interaction

The protein–protein interaction between menin and mixed-lineage leukemia 1 (MLL1) plays an important role in development of acute leukemia with translocations of the <i>MLL1</i> gene and in solid tumors. Here, we report the development of a new generation of menin–MLL1 inhibitors identified by structure-based optimization of the thieno­pyrimidine class of compounds. This work resulted in compound <b>28</b> (<b>MI-1481</b>), which showed very potent inhibition of the menin–MLL1 interaction (IC₅₀ = 3.6 nM), representing the most potent reversible menin–MLL1 inhibitor reported to date. The crystal structure of the menin-<b>28</b> complex revealed a hydrogen bond with Glu366 and hydrophobic interactions, which contributed to strong inhibitory activity of <b>28</b>. Compound <b>28</b> also demonstrates pronounced activity in MLL leukemia cells and <i>in vivo</i> in MLL leukemia models. Thus, <b>28</b> is a valuable menin–MLL1 inhibitor that can be used for potential therapeutic applications and in further studies regarding the role of menin in cancer

Menin regulates the serine biosynthetic pathway in Ewing sarcoma

Developmental transcription programs are epigenetically regulated by multiâ protein complexes, including the meninâ and MLLâ containing trithorax (TrxG) complexes, which promote gene transcription by depositing the H3K4me3 activating mark at target gene promoters. We recently reported that in Ewing sarcoma, MLL1 (lysine methyltransferase 2A, KMT2A) and menin are overexpressed and function as oncogenes. Small molecule inhibition of the meninâ MLL interaction leads to loss of menin and MLL1 protein expression, and to inhibition of growth and tumorigenicity. Here, we have investigated the mechanistic basis of meninâ MLLâ mediated oncogenic activity in Ewing sarcoma. Bromouridine sequencing (Bruâ seq) was performed to identify changes in nascent gene transcription in Ewing sarcoma cells, following exposure to the meninâ MLL interaction inhibitor MIâ 503. Meninâ MLL inhibition resulted in early and widespread reprogramming of metabolic processes. In particular, the serine biosynthetic pathway (SSP) was the pathway most significantly affected by MIâ 503 treatment. Baseline expression of SSP genes and proteins (PHGDH, PSAT1, and PSPH), and metabolic flux through the SSP were confirmed to be high in Ewing sarcoma. In addition, inhibition of PHGDH resulted in reduced cell proliferation, viability, and tumor growth in vivo, revealing a key dependency of Ewing sarcoma on the SSP. Loss of function studies validated a mechanistic link between menin and the SSP. Specifically, inhibition of menin resulted in diminished expression of SSP genes, reduced H3K4me3 enrichment at the PHGDH promoter, and complete abrogation of de novo serine and glycine biosynthesis, as demonstrated by metabolic tracing studies with 13Câ labeled glucose. These data demonstrate that the SSP is highly active in Ewing sarcoma and that its oncogenic activation is maintained, at least in part, by meninâ dependent epigenetic mechanisms involving trithorax complexes. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144706/1/path5085_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144706/2/path5085.pd

Complexity of Blocking Bivalent Protein–Protein Interactions: Development of a Highly Potent Inhibitor of the Menin–Mixed-Lineage Leukemia Interaction

The protein–protein interaction between menin and mixed-lineage leukemia 1 (MLL1) plays an important role in development of acute leukemia with translocations of the <i>MLL1</i> gene and in solid tumors. Here, we report the development of a new generation of menin–MLL1 inhibitors identified by structure-based optimization of the thieno­pyrimidine class of compounds. This work resulted in compound <b>28</b> (<b>MI-1481</b>), which showed very potent inhibition of the menin–MLL1 interaction (IC₅₀ = 3.6 nM), representing the most potent reversible menin–MLL1 inhibitor reported to date. The crystal structure of the menin-<b>28</b> complex revealed a hydrogen bond with Glu366 and hydrophobic interactions, which contributed to strong inhibitory activity of <b>28</b>. Compound <b>28</b> also demonstrates pronounced activity in MLL leukemia cells and <i>in vivo</i> in MLL leukemia models. Thus, <b>28</b> is a valuable menin–MLL1 inhibitor that can be used for potential therapeutic applications and in further studies regarding the role of menin in cancer