MELK inhibition promotes megakaryopoiesis and platelet recovery in immune thrombocytopenia through ERK–cofilin signaling
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE322507 | GEO | 2026/04/02
REPOSITORIES: GEO
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Project description:To investigate whether MELK phosphorylates Cofilin-1 at residue Threonine 70 (T70), we performed a phosphoproteomic validation using immunoprecipitation coupled with mass spectrometry (IP-LC-MS/MS). HEK293T cells were divided into three experimental groups: (1) MOCK control (Empty Vector), (2) MELK overexpression, and (3) MELK overexpression treated with the inhibitor OTSSP167. Endogenous Cofilin-1 was enriched by immunoprecipitation. The study aimed to identify and quantify the phosphorylation status of Cofilin-1, specifically focusing on the T70 site, and to assess the impact of MELK kinase activity and its inhibition by OTSSP167 on this phosphorylation event.
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Project description:Survival kinase MELK has been shown to be important for proliferation of several tumors such as brain, breast or prostate. MELK expression is elevated in cutaneous melanoma, therefore, we analyzed the role of MELK in melanoma. Inhibition of MELK in melanoma cell lines resulted in decreased proliferation, increased cell death and decreased invasion. MELK expression is regulated through MAP kinase pathway and inhibition of MAPK pathway leads to diminished MELK expression. Finally, inhibition of MELK reduces tumor size in nude mice.
2020-12-30 | GSE83907 | GEO
Project description:Maternal Embryonic Leucine Zipper Kinase (MELK), a Ser/Thr protein kinase, is highly over expressed in stem and cancer cells. The oncogenic role of MELK is attributed to its capacity to disable critical cell cycle checkpoints and to enhance replication. Most functional studies have relied on the use of siRNA/shRNA-mediated gene silencing, but this is often compromised by off target effects. Here we present the cellular validation of a novel, potent and selective small molecule MELK inhibitor, MELK-T1, which has enabled us to explore the biological function of MELK. Strikingly, the binding of MELK-T1 to endogenous MELK triggers a rapid and proteasome dependent degradation of the MELK protein. Treatment of MCF-7 breast adenocarcinoma cells with MELK-T1 leads to an accumulation of stalled replication forks and double strand breaks, followed by a replicative senescence phenotype. This phenotype correlates with a rapid and long-lasting ATM activation and phosphorylation of CHK2. Furthermore, MELK-T1 induces strong phosphorylation of p53 and prolonged up-regulation of p21. Our data generated with MELK-T1 indicate that MELK is a key stimulator of proliferation by its ability to increase the threshold for DNA damage tolerance. Thus, targeting MELK by combined inhibition of its catalytic function and inhibitor-induced degradation might sensitize tumors to DNA-damaging agents or radiation therapy, by lowering the DNA damage threshold.
2015-12-11 | GSE62477 | GEO
Project description:A cross-species analysis identified MELK as a potential therapeutic target in prostate cancer. To further elucidate the functional role of MELK in prostate cancer cells, we aimed to identify MELK-regulated genes. C4-2b cells were either treated with a small-molecule MELK inhibitor (OTSSP167), or transfected with siRNAs targeting MELK. Differentially expressed genes were identified using next-generation sequencing. Our results demonstrate that MELK promotes the expression of genes associated with tumour progression in prostate cancer cells.
2018-02-05 | GSE94570 | GEO
Project description:Glioblastoma multiforme (GBM) is a highly lethal brain tumor. Due to resistance to current therapies, patient prognosis remains poor and development of novel and effective GBM therapy is crucial. Glioma stem cells (GSCs) have gained attention as therapeutic target in GBM due to their relative resistance to current therapies and potent tumor-initiating ability. Recent studies including our own identified that the mitotic kinase, maternal embryonic leucine-zipper kinase (MELK), is highly expressed in GBM tissues, specifically in GSCs, and its expression is inversely correlated with the post-surgical survival period of GBM patients. In addition, patient-derived GSCs depend on MELK for their survival and growth both in vitro and in vivo. Here, we provide evidence that the kinase activity of MELK is essential for the action of MELK in GSCs and vital for GBM growth. We utilized in silico structure-based analysis for protein-compound interaction to predict that a recently identified small molecule, Compound 1 (C1), binds to the kinase-active site of MELK protein and eliminates MELK kinase activity in nanomolar concentrations. When treated with C1, GSCs undergo mitotic arrest and subsequent cellular apoptosis in vitro, a phenotype identical to that observed using MELK shRNA-mediated knockdown. C1 treatment strongly induces tumor cell apoptosis in slice cultures of GBM surgical specimens and attenuates growth of mouse intracranial tumors derived from GSCs in a dose-dependent manner. Lastly, C1 treatment sensitizes GSCs to radiation treatment. Collectively, these data indicate that targeting MELK kinase activity is a promising approach to attenuate GBM growth by eliminating GSCs in tumors.
2013-08-28 | GSE50227 | GEO
Project description:Triple-negative breast cancer (TNBC) has high relapse and metastasis rates and a high proportion of cancer stem-like cells (CSCs), which possess self-renewal and tumor initiation capacity. MELK (maternal embryonic leucine zipper kinase), a protein kinase of the Snf1/AMPK kinase family, is known to promote CSC maintenance and malignant transformation. Our study showed that MELK knockdown using siRNA or MELK inhibition using the MELK inhibitor MELK-In-17 significantly reduced invasiveness, reversed epithelial-to-mesenchymal transition (EMT), and reduced CSC self-renewal and maintenance in TNBC cells. Nude mice injected with CRISPR MELK-knockout MDA-MB-231 cells exhibited suppression of lung metastasis and improved overall survival compared with mice injected with control cells. Furthermore, MELK-In-17 suppressed 4T1 tumor growth in syngeneic BALB/c mice. Our findings indicate that MELK supports metastasis by promoting EMT and the CSC phenotype in TNBC. In our microarray analysis, we identified potential downstream targets of MELK, including STAT5 and NF-kB target genes, as well as genes involved in tumor progression and metastasis (i.e., EMT, angiogenesis, hypoxia, and apical junction). EMT was the most strongly enriched hallmark among genes highly expressed in Cas9-p15 control cells, further confirming that EMT is a major factor contributing to MELK-induced metastasis in TNBC. We also identified a direct physical interaction partner (PRKAB2) of MELK and a set of intermediate proteins (CDC25B, EZH2, FOXM1, JUN, MAP3K5, PRKAB1, PRKAB2, and SMAD2), suggesting that these proteins are key components of MELK-induced signal transduction.
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Project description:Glioblastoma multiforme (GBM) is a highly lethal brain tumor. Due to resistance to current therapies, patient prognosis remains poor and development of novel and effective GBM therapy is crucial. Glioma stem cells (GSCs) have gained attention as therapeutic target in GBM due to their relative resistance to current therapies and potent tumor-initiating ability. Recent studies including our own identified that the mitotic kinase, maternal embryonic leucine-zipper kinase (MELK), is highly expressed in GBM tissues, specifically in GSCs, and its expression is inversely correlated with the post-surgical survival period of GBM patients. In addition, patient-derived GSCs depend on MELK for their survival and growth both in vitro and in vivo. Here, we provide evidence that the kinase activity of MELK is essential for the action of MELK in GSCs and vital for GBM growth. We utilized in silico structure-based analysis for protein-compound interaction to predict that a recently identified small molecule, Compound 1 (C1), binds to the kinase-active site of MELK protein and eliminates MELK kinase activity in nanomolar concentrations. When treated with C1, GSCs undergo mitotic arrest and subsequent cellular apoptosis in vitro, a phenotype identical to that observed using MELK shRNA-mediated knockdown. C1 treatment strongly induces tumor cell apoptosis in slice cultures of GBM surgical specimens and attenuates growth of mouse intracranial tumors derived from GSCs in a dose-dependent manner. Lastly, C1 treatment sensitizes GSCs to radiation treatment. Collectively, these data indicate that targeting MELK kinase activity is a promising approach to attenuate GBM growth by eliminating GSCs in tumors. Microarray-based expression analysis of glioma stem cells treated with MELK-signaling inhibitors
2013-08-28 | E-GEOD-50227 | biostudies-arrayexpress
Project description:The key objectives of this study were to evaluate the selectivity profiles of three MELK inhibitors, 8a, HTH, and OTS, using a cell-based assay, in order to identify a highly selective inhibitor to subsequently investigate MELK function. To this end, we utilized a chemical proteomics approach called multiplexed kinase inhibitor beads/mass spectrometry (MIB/MS) to characterize the selectivity of these MELK inhibitors in TNBC cells.
2020-01-09 | PXD016022 | Pride
Project description:Melanoma accounts for over 80% of skin cancer-related deaths and current therapies provide only short-term benefit to patients. Here, we show in melanoma cells that maternal embryonic leucine zipper kinase (MELK) is transcriptionally upregulated by the MAP kinase pathway via transcription factor E2F1. MELK knockdown or pharmacological inhibition blocked melanoma growth and enhanced the effectiveness of BRAFV600E inhibitor against melanoma cells. To identify mediators of MELK function, we performed stable isotope labeling with amino acids in cell culture (SILAC) and identified 469 proteins that had downregulated phosphorylation after MELK inhibition. Remarkably, 139 of these proteins were previously reported as substrates of BRAF or MEK, demonstrating that MELK is an important downstream mediator of the MAPK pathway. Furthermore, we show that MELK promotes melanoma growth by activating NF-B pathway activity via Sequestosome 1 (SQSTM1/p62). Collectively, these results underpin an important role for MELK in melanoma growth, downstream of the MAPK pathway.
2017-12-07 | PXD007872 | Pride
Project description:Combinatorial actions of relatively few transcription factors control hematopoietic differentiation. To investigate this process in erythro-megakaryopoiesis, we correlated the genome-wide chromatin occupancy signatures of four master hematopoietic transcription factors (GATA1, GATA2, SCL/TAL1 and FLI1) and three diagnostic histone modification marks with the gene expression changes that occur during development of primary megakaryocytes (MEG) and erythroblasts (ERY) from murine fetal liver hematopoietic stem/progenitor cells. We identified a robust, genome-wide mechanism of MEG-specific lineage priming by a previously described stem/progenitor cell-expressed transcription factor heptad (GATA2, LYL1, SCL/TAL1, FLI1, ERG, RUNX1, LMO2) binding to MEG-specific cis-regulatory modules in multipotential hematopoietic progenitors. This is followed by genome-wide GATA factor switching that mediates further induction of MEG-specific genes following lineage commitment. Interaction between GATA and ETS factors appears to be a key determinant of these processes. In contrast, ERY-specific lineage priming occurs is biased toward GATA2-independent mechanisms. In addition to its role in MEG lineage priming, GATA2 plays an extensive role in late megakaryopoiesis as a transcriptional repressor at loci defined by a specific DNA signature. Our findings reveal important new insights into how ERY and MEG lineages arise from a common bipotential precursor via overlapping and divergent functions of shared hematopoietic transcription factors. Gene expression changes during the development of primary megakaryocytes (MEG) and erythroblasts (ERY) from murine fetal liver hematopoietic stem/progenitor cells
2013-08-09 | E-GEOD-49664 | biostudies-arrayexpress