MAP kinase-interacting kinases (MNK1 and MNK2) are often activated downstream of ERK and p38 MAPK in the MAP kinase family. The role of MNKs in the development and progression of solid tumors and ...hematological malignancies has been widely discussed, particularly in the context of cap dependent translation, regulated by phosphorylation of eIF4E. MNK/eIF4E axis is involved in the expression of pro angiogenic, antiapoptotic, cell cycle, and motility proteins, such as MCL1, VEGF, MMP3, SNAIL, SMAD2, β-catenin or cyclin D1, and is essential during Ras and c Myc-induced transformation. MNK1/2 emerged as eligible targets for drug discovery in oncology, based on the antitumor effects observed in genetic knockout and RNA interference experiments and at the same time lack of adverse effects in dual knockout animals. There is a high interest in the development of pharmacological inhibitors of MNK1/2 as not only tools for further basic research studies but also potential drugs in diseases characterized by deregulated translation. Unfortunately, the role of MNK1/2 in cancer still remains elusive due to the absence of potent and selective probes. Moreover, in many instances, hypotheses have been built reliant upon unspecific MNK1/2 inhibitors such as CGP57380 or cercosporamide. Lately, the first two clinical programs targeting MNKs in oncology have been revealed (eFT508 and BAY 1143269), although several other MNK programs are currently running at the preclinical stage. This review aims to provide an overview of recent progress in the development of MNK inhibitors.
Tumor hypoxia confers resistance to many modalities of anticancer therapy. The endoplasmic reticulum (ER) is highly sensitive to severe hypoxic stress and results in the activation of the unfolded ...protein response. ATF4 is the main transcriptional regulator of the cellular hypoxic response to the UPR and activates genes that promote restoration of normal ER function and survival under hypoxia. Elevated expression of ATF4 is associated with resistance to current chemotherapeutic drugs including DNA-interactive and damaging agents, nonsteroidal anti-inflammatory drugs and proteasome inhibitors. ATF4 decreases the antitumor activity of chemotherapy by mechanisms involving expression of genes involved in oxidative stress resistance, redox homeostasis and inhibitors of apoptosis. ATF4 plays also a crucial role in resistance to proteasomal inhibitor bortezomib (PS-341) by the induction of prosurvival pathways, such as autophagy, that can relieve the protein overload in bortezomib treated cells. Inhibition of ATF4 represents an attractive stand-alone therapy as well as an opportunity to enhance the efficacy of current chemotherapeutic agents without causing high tissue toxicity to normal tissues.
Melanoma can be stratified into unique subtypes based on distinct pathologies. The acral/mucosal melanoma subtype is characterized by aberrant and constitutive activation of the proto-oncogene ...receptor tyrosine kinase C-KIT, which drives tumorigenesis. Treatment of these melanoma patients with C-KIT inhibitors has proven challenging, prompting us to investigate the downstream effectors of the C-KIT receptor. We determined that C-KIT stimulates MAP kinase-interacting serine/threonine kinases 1 and 2 (MNK1/2), which phosphorylate eukaryotic translation initiation factor 4E (eIF4E) and render it oncogenic. Depletion of MNK1/2 in melanoma cells with oncogenic C-KIT inhibited cell migration and mRNA translation of the transcriptional repressor SNAI1 and the cell cycle gene CCNE1. This suggested that blocking MNK1/2 activity may inhibit tumor progression, at least in part, by blocking translation initiation of mRNAs encoding cell migration proteins. Moreover, we developed an MNK1/2 inhibitor (SEL201), and found that SEL201-treated KIT-mutant melanoma cells had lower oncogenicity and reduced metastatic ability. Clinically, tumors from melanoma patients harboring KIT mutations displayed a marked increase in MNK1 and phospho-eIF4E. Thus, our studies indicate that blocking MNK1/2 exerts potent antimelanoma effects and support blocking MNK1/2 as a potential strategy to treat patients positive for KIT mutations.
Sepsis is the leading cause of death in intensive care units worldwide. Current treatments of sepsis are largely supportive and clinical trials using specific pharmacotherapy for sepsis have failed ...to improve outcomes. Here, we used the lipopolysaccharide (LPS)-stimulated mouse RAW264.7 cell line and AlphaLisa assay for TNFa as a readout to perform a supervised drug repurposing screen for sepsis treatment with compounds targeting epigenetic enzymes, including kinases. We identified the SCH772984 compound, an extracellular signal-regulated kinase (ERK) 1/2 inhibitor, as an effective blocker of TNFa production in vitro. RNA-Seq of the SCH772984-treated RAW264.7 cells at 1, 4, and 24 h time points of LPS challenge followed by functional annotation of differentially expressed genes highlighted the suppression of cellular pathways related to the immune system. SCH772984 treatment improved survival in the LPS-induced lethal endotoxemia and cecal ligation and puncture (CLP) mouse models of sepsis, and reduced plasma levels of Ccl2/Mcp1. Functional analyses of RNA-seq datasets for kidney, lung, liver, and heart tissues from SCH772984-treated animals collected at 6 h and 12 h post-CLP revealed a significant downregulation of pathways related to the immune response and platelets activation but upregulation of the extracellular matrix organization and retinoic acid signaling pathways. Thus, this study defined transcriptome signatures of SCH772984 action in vitro and in vivo, an agent that has the potential to improve sepsis outcome.
The lack of oxygen delivery to tumor cells has profound consequences for tumor growth and correlates with poor prognosis.
Some tumors contain regions of very severe hypoxia called anoxia, which ...constitutes a functionally different state to hypoxia.
In response to anoxia, mammalian cells induce coordinated cytoprotective programs that are critical for tumor survival: the
unfolded protein response and integrated stress response. Therefore, targeting additional components of anoxic pathways, besides
the hypoxia-inducible response, may be effective for future anticancer therapies.
Abstract Background and purpose Tumour hypoxia contributes to failure of cancer treatment through its ability to protect against therapy and adversely influence tumour biology. In particular, several ...studies suggest that hypoxia promotes metastasis. Hypoxia-induced cellular changes are mediated by oxygen-sensitive signaling pathways that activate downstream transcription factors. We have investigated the induction and transcriptional regulation of a novel metastasis-associated gene, LAMP3 during hypoxia. Materials and methods Microarray, quantitative PCR, Western blot analysis and immunohistochemistry were used to investigate hypoxic regulation of LAMP3 . The mechanism for LAMP3 induction was investigated using transient RNAi and stable shRNA targeting components of the hypoxic response. Endoplasmic reticulum stress inducing agents, including proteasome inhibitors were assessed for their ability to regulate LAMP3. Results LAMP3 is strongly induced by hypoxia at both the mRNA and protein levels in a large panel of human tumour cell lines. Induction of LAMP3 occurs as a consequence of the activation of the PERK/eIF2α/ATF4 arm of the unfolded protein response (UPR) and is independent of HIF-1α. LAMP3 is expressed heterogeneously within the microenvironment of tumours, overexpressed in breast cancer, and increases in tumours treated with avastin. Conclusions These data identify LAMP3 as a novel hypoxia-inducible gene regulated by the UPR. LAMP3 is a new candidate biomarker of UPR activation by hypoxia in tumours and is a potential mediator of hypoxia-induced metastasis.
A safe and efficient therapy for patients with the bone marrow failure syndrome Diamond-Blackfan Anemia (DBA) is urgently needed. To identify novel drug candidates for DBA, a small molecule screen ...was performed using c-Kit positive E14.5 fetal liver cells from a DBA mouse model in which the DBA phenotype is induced upon doxycycline (DOX)-inducible silencing of Rps19, the most frequently mutated gene in DBA (Jaako et al. PMID: 21989989). Test compounds were added 24 hours after cell seeding and DOX addition. After four days the number of live metabolically active cells in each well was estimated based on quantitation of intracellular ATP. Fifteen commercial annotated small-molecule libraries (3 800 molecules) and 10 500 selected compounds from a diverse compound library were screened. Between the screens we identified 20 molecules that reproducibly increased proliferation of rps19-deficient erythroid progenitors 4-8 fold in a concentration-dependent manner. Hits from annotated libraries included inhibitors of TGFb receptor, DYRK and Casein kinases. The most potent hits however were compounds in a series of thienopyridines, with an unknown target profile, but with a core structure suggesting kinase inhibition activity. Database searches revealed that the structure-activity relationships (SAR) of 12 active and 10 inactive analogues were similar to that of a series of thienopyridines previously reported as bone anabolic agents by unknown mechanism (Saito et al. PMID: 23453217). The most potent analogues described by Saito et al. as bone anabolic agents were synthesized, and the compounds rescue also RPS19-deficient erythroid cell proliferation in a potent manner (EC50= 20-50 nM). In an attempt to identify the molecular target of these compounds, six actives including thienopyridines 15k and 15w were subjected to kinase profiling against 468 kinases (DiscoverX). Three of the compounds targeted cyclin- dependent kinases CDK8 and its paralog CDK19, and in particular the most potent molecule (15w) is a highly selective CDK8 inhibitor. To confirm whether CDK8 inhibition underlies the rescue of the DBA phenotype, structurally unrelated and potent CDK8 inhibitors including CCT-251545, Senexin A, Senexin B, and Sel120-34A were also evaluated. All tested CDK8-inhibitors rescue proliferation and erythroid maturation of c-kit+ cells from the DBA mouse in a concentration-dependent manner. To further investigate the potential of CDK8 as a therapeutic target in DBA several CDK8 inhibitors were evaluated in erythroid cultures of primary DBA patient cells. CDK8 inhibitors 15w, Senexin B and Sel120-34A increase erythroid progenitor proliferation 5-10 fold of CD34+ peripheral blood cells from three DBA patients (RPS19, RPS26, RPL35a mutations), and increase the fraction of transferrin receptor (CD71) and glycophorin A positive cells in culture. Healthy CD34+ peripheral blood treated with CDK8 inhibitors show no increase in proliferation. Finally, we show that bone marrow failure and anemia in the DBA mouse model is partially rescued (RBC and Hemoglobin levels, p<0.001) after 8 daily oral doses (30mg/kg) of CDK8 inhibitor Sel120-34A. Since CDK8 is the regulatory subunit of the Mediator complex, acting as a regulator of RNA pol II transcription the therapeutic effect of CDK8 inhibitors likely involves direct changes in gene expression. RNA-Seq and gene set enrichment analysis on DBA mouse model cells treated with CDK8 inhibitor Sel120-34A shows p53 target genes are induced in RPS19-deficient cells and that CDK8 inhibitor treatment reverses this change, agreeing with previous reports that CDK8 can regulate transcription of p53 target genes. We confirm CDK8-inhibitor treatment reverses nuclear localization of p21 in RPS19-deficient cell lines. The most significant effect in gene set analysis however is the rescue of MYC-target gene expression, including increased expression of several ribosomal protein genes. In summary, selective and potent CDK8 inhibitors dramatically improve proliferation and maturation of erythroid progenitors in an animal model for DBA and in primary DBA patient cells. The therapeutic effect involves reduced expression of p53-target genes and increased expression of MYC-target genes. Given lack of adverse effects at effective doses in vivo, further development of SEL120-34A as a treatment for DBA patients is warranted.
Rzymski:Selvita S.A.: Employment, Equity Ownership. Johansson:LU Holding: Patents & Royalties. Lundbäck:LU Holding: Patents & Royalties. Mazan:Selvita S.A.: Employment. Majewska:Selvita S.A.: Employment. Brzózka:Selvita S.A.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Flygare:LU Holding: Patents & Royalties: Patent.
Cyclin-dependent kinase (CDK) inhibitors have been developed as potential anticancer therapeutics and several nonselective compounds are currently in advanced clinical trials. This review is focused ...on the key biological roles of CDK8 kinase, which provide a proof-of-principle for continued efforts toward effective cancer treatment, targeting activity of this CDK family member. Among currently identified kinase inhibitors, several displayed significant selectivity for CDK8 and notably the effectiveness in targeting cancer specific gene expression programs. Structural features of CDK8 and available ligands were discussed from a perspective of the rational drug design process. Current state of the art confirms that further development of CDK8 inhibitors will translate into targeted therapies in oncology. This article is part of a Special Issue entitled:Inhibitors of Protein Kinases.
•Impeded mRNA synthesis contributes to the effectiveness of pan-CDK inhibitors.•Numerous studies indicate that CDK8/cyclin C can function as a bona fide oncogene.•Oncogenic functions of CDK8 are related to the modulation of transcription programs.•Unique structure of CDK8/CycC among other CDKs enables SBDD of selective inhibitors.•First selective CDK8/cyclin C inhibitors are currently in preclinical development.
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