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      MAPKAPK2 plays a crucial role in the progression of head and neck squamous cell carcinoma by regulating transcript stability

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          Abstract

          Background

          Head and neck squamous-cell carcinoma (HNSCC) ranks sixth among cancers worldwide. Though several molecular mechanisms of tumor initiation and progression of HNSCC are known, others remain unclear. Significance of p38/MAPKAPK2 (Mitogen-activated protein kinase-activated protein kinase-2) pathway in cell stress and inflammation is well established and its role in tumor development is being widely studied.

          Methods

          We have elucidated the role of MAPKAPK2 (MK2) in HNSCC pathogenesis using clinical tissue samples, MK2-knockdown (MK2 KD) cells and heterotropic xenograft mice model.

          Results

          In patient-derived tissue samples, we observed that MK2 is reproducibly overexpressed. Increased stability of cyclin-dependent kinase inhibitor 1B (p27), mitogen-activated protein kinase phosphatase-1 (MKP-1) transcripts and decreased half-life of tumor necrosis factor-alpha (TNF-α) and vascular endothelial growth factor (VEGF) transcripts in MK2 KD cells suggests that MK2 regulates their transcript stability. In vivo xenograft experiments established that knockdown of MK2 attenuates course of tumor progression in immunocompromised mice.

          Conclusion

          Altogether, MK2 is responsible for regulating the transcript stability and is functionally important to modulate HNSCC pathogenesis.

          Electronic supplementary material

          The online version of this article (10.1186/s13046-019-1167-2) contains supplementary material, which is available to authorized users.

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          Most cited references 27

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          MK2 Phosphorylates RIPK1 to Prevent TNF-Induced Cell Death

          Summary TNF is an inflammatory cytokine that upon binding to its receptor, TNFR1, can drive cytokine production, cell survival, or cell death. TNFR1 stimulation causes activation of NF-κB, p38α, and its downstream effector kinase MK2, thereby promoting transcription, mRNA stabilization, and translation of target genes. Here we show that TNF-induced activation of MK2 results in global RIPK1 phosphorylation. MK2 directly phosphorylates RIPK1 at residue S321, which inhibits its ability to bind FADD/caspase-8 and induce RIPK1-kinase-dependent apoptosis and necroptosis. Consistently, a phospho-mimetic S321D RIPK1 mutation limits TNF-induced death. Mechanistically, we find that phosphorylation of S321 inhibits RIPK1 kinase activation. We further show that cytosolic RIPK1 contributes to complex-II-mediated cell death, independent of its recruitment to complex-I, suggesting that complex-II originates from both RIPK1 in complex-I and cytosolic RIPK1. Thus, MK2-mediated phosphorylation of RIPK1 serves as a checkpoint within the TNF signaling pathway that integrates cell survival and cytokine production.
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            DNA damage activates a spatially distinct late cytoplasmic cell-cycle checkpoint network controlled by MK2-mediated RNA stabilization.

            Following genotoxic stress, cells activate a complex kinase-based signaling network to arrest the cell cycle and initiate DNA repair. p53-defective tumor cells rewire their checkpoint response and become dependent on the p38/MK2 pathway for survival after DNA damage, despite a functional ATR-Chk1 pathway. We used functional genetics to dissect the contributions of Chk1 and MK2 to checkpoint control. We show that nuclear Chk1 activity is essential to establish a G(2)/M checkpoint, while cytoplasmic MK2 activity is critical for prolonged checkpoint maintenance through a process of posttranscriptional mRNA stabilization. Following DNA damage, the p38/MK2 complex relocalizes from nucleus to cytoplasm where MK2 phosphorylates hnRNPA0, to stabilize Gadd45α mRNA, while p38 phosphorylates and releases the translational inhibitor TIAR. In addition, MK2 phosphorylates PARN, blocking Gadd45α mRNA degradation. Gadd45α functions within a positive feedback loop, sustaining the MK2-dependent cytoplasmic sequestration of Cdc25B/C to block mitotic entry in the presence of unrepaired DNA damage. Our findings demonstrate a critical role for the MK2 pathway in the posttranscriptional regulation of gene expression as part of the DNA damage response in cancer cells. Copyright © 2010 Elsevier Inc. All rights reserved.
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              Clonogenic assay with established human tumour xenografts: correlation of in vitro to in vivo activity as a basis for anticancer drug discovery.

              Pluripotent cells can be grown in clonogenic assays. The tumour stem-cell fraction, which accounts for <0.4% of the total cells, and which is considered the most relevant cell type in the development of metastases and recurrences, is able to divide and to form colonies in a semisolid matrix (agar or methylcellulose). Major applications of the tumour clonogenic assay (TCA) are chemosensitivity testing of tumours and xenografts, and for assessments within drug discovery programmes. Of critical relevance for the usefulness of the TCA is whether it can predict sensitivity or resistance towards clinically used agents. When we compared the response of human tumours established as xenografts in nude mice in the TCA in vitro to that of the clinical response, 62% of the comparisons for drug sensitivity, and 92% of the comparisons for drug resistance were correct. The same percentage of true/false observations was found when tumours were tested after serial passage in nude mice in the TCA in vitro and their response compared to in vivo activity in corresponding xenografts (60% and 90%, respectively). The highest correct predictive values were, however, found when the clinical response of tumours was compared to their explants established in the nude mouse and treated in vivo. Of 80 comparisons performed, we observed a correct prediction for tumour resistance in 97% and for tumour sensitivity in 90%. In our opinion, the TCA with established human tumour xenografts has an important role in current drug discovery strategies. We therefore included the TCA as secondary assay in our approach to anticancer drug discovery and found that a number of novel agents were active; these are now in advanced preclinical development or clinical trials. Thus, the tumour clonogenic assay has proven predictive value in the chemosensitivity testing of standard and experimental anticancer drugs.
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                Author and article information

                Contributors
                sourabhsoniplp@gmail.com
                drsaroch@gmail.com
                ssst419@hotmail.com
                narendra@ihbt.res.in
                +919816747680 , yogendra@ihbt.res.in
                Journal
                J Exp Clin Cancer Res
                J. Exp. Clin. Cancer Res
                Journal of Experimental & Clinical Cancer Research : CR
                BioMed Central (London )
                0392-9078
                1756-9966
                25 April 2019
                25 April 2019
                2019
                : 38
                Affiliations
                [1 ]ISNI 0000 0004 0500 553X, GRID grid.417640.0, Pharmacology and Toxicology Laboratory, Food and Nutraceuticals Division, , CSIR-Institute of Himalayan Bioresource Technology (CSIR-IHBT), ; Palampur, H.P. India
                [2 ]Department of Otorhinolaryngology, Head and Neck Surgery, Dr. Rajendra Prasad Government Medical College and Hospital (RPGMCH), Kangra, H.P. India
                [3 ]Department of Pathology, Dr. Rajendra Prasad Government Medical College and Hospital (RPGMCH), Kangra, H.P. India
                [4 ]GRID grid.469887.c, Academy of Scientific and Innovative Research, ; Chennai, Tamil Nadu India
                Article
                1167
                10.1186/s13046-019-1167-2
                6482562
                31023373
                © The Author(s). 2019

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100001332, Council for Scientific and Industrial Research;
                Award ID: MLP0039
                Award ID: MLP0204
                Categories
                Research
                Custom metadata
                © The Author(s) 2019

                Oncology & Radiotherapy

                xenograft, hnscc, pathogenesis, mapkapk2, transcript stability, rbps

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