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      NEK2 Promotes Aerobic Glycolysis in Multiple Myeloma Through Regulating Splicing of Pyruvate Kinase

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          Abstract

          Background

          Aerobic glycolysis, a hallmark of cancer, is characterized by increased metabolism of glucose and production of lactate in normaxia. Recently, pyruvate kinase M2 (PKM2) has been identified as a key player for regulating aerobic glycolysis and promoting tumor cell proliferation and survival.

          Methods

          Tandem affinity purification followed up by mass spectrometry (TAP-MS) and co-immunoprecipitation (Co-IP) were used to study the interaction between NIMA (never in mitosis gene A)-related kinase 2 (NEK2) and heterogeneous nuclear ribonucleoproteins (hnRNP) A1/2. RNA immunoprecipitation (RIP) was performed to identify NEK2 binding to PKM pre-mRNA sequence. Chromatin-immunoprecipitation (ChIP)-PCR was performed to analyze a transcriptional regulation of NEK2 by c-Myc. Western blot and real-time PCR were executed to analyze the regulation of PKM2 by NEK2.

          Results

          NEK2 regulates the alternative splicing of PKM immature RNA in multiple myeloma cells by interacting with hnRNPA1/2. RIP shows that NEK2 binds to the intronic sequence flanking exon 9 of PKM pre-mRNA. Knockdown of NEK2 decreases the ratio of PKM2/PKM1 and also other aerobic glycolysis genes including GLUT4, HK2, ENO1, LDHA, and MCT4. Myeloma patients with high expression of NEK2 and PKM2 have lower event-free survival and overall survival. Our data indicate that NEK2 is transcriptionally regulated by c-Myc in myeloma cells. Ectopic expression of NEK2 partially rescues growth inhibition and cell death induced by silenced c-Myc.

          Conclusions

          Our studies demonstrate that NEK2 promotes aerobic glycolysis through regulating splicing of PKM and increasing the PKM2/PKM1 ratio in myeloma cells which contributes to its oncogenic activity.

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          Most cited references39

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          ERK1/2-dependent phosphorylation and nuclear translocation of PKM2 promotes the Warburg effect

          SUMMARY Pyruvate kinase M2 (PKM2) is upregulated in multiple cancer types and contributes to the Warburg effect by unclarified mechanisms. Here we demonstrate that EGFR-activated ERK2 binds directly to PKM2 I429/L431 via the ERK2 docking groove and phosphorylates PKM2 Ser37 but not PKM1. Phosphorylated PKM2 Ser37 recruits PIN1 for cis-trans isomerization of PKM2, which leads to PKM2 binding to importin α5 and nuclear translocation. Nuclear PKM2, acting as a coactivator of β-catenin, induces c-Myc expression, resulting in the upregulation of GLUT1, LDHA, and, in a positive feedback loop, PTB-dependent PKM2 expression. Replacement of wild type PKM2 with a nuclear translocation-deficient mutant (S37A) blocks the EGFR-promoted Warburg effect and brain tumor development. In addition, levels of PKM2 S37 phosphorylation correlate with EGFR and ERK1/2 activity in human glioblastoma specimens. Our findings highlight the importance of nuclear functions of PKM2 in the Warburg effect and tumorigenesis.
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            Mammalian target of rapamycin up-regulation of pyruvate kinase isoenzyme type M2 is critical for aerobic glycolysis and tumor growth.

            Although aerobic glycolysis (the Warburg effect) is a hallmark of cancer, key questions, including when, how, and why cancer cells become highly glycolytic, remain less clear. For a largely unknown regulatory mechanism, a rate-limiting glycolytic enzyme pyruvate kinase M2 (PKM2) isoform is exclusively expressed in embryonic, proliferating, and tumor cells, and plays an essential role in tumor metabolism and growth. Because the receptor tyrosine kinase/PI3K/AKT/mammalian target of rapamycin (RTK/PI3K/AKT/mTOR) signaling cascade is a frequently altered pathway in cancer, we explored its potential role in cancer metabolism. We identified mTOR as a central activator of the Warburg effect by inducing PKM2 and other glycolytic enzymes under normoxic conditions. PKM2 level was augmented in mouse kidney tumors due to deficiency of tuberous sclerosis complex 2 and consequent mTOR activation, and was reduced in human cancer cells by mTOR suppression. mTOR up-regulation of PKM2 expression was through hypoxia-inducible factor 1α (HIF1α)-mediated transcription activation, and c-Myc-heterogeneous nuclear ribonucleoproteins (hnRNPs)-dependent regulation of PKM2 gene splicing. Disruption of PKM2 suppressed oncogenic mTOR-mediated tumorigenesis. Unlike normal cells, mTOR hyperactive cells were more sensitive to inhibition of mTOR or glycolysis. Dual suppression of mTOR and glycolysis synergistically blunted the proliferation and tumor development of mTOR hyperactive cells. Even though aerobic glycolysis is not required for breach of senescence for immortalization and transformation, the frequently deregulated mTOR signaling during multistep oncogenic processes could contribute to the development of the Warburg effect in many cancers. Components of the mTOR/HIF1α/Myc-hnRNPs/PKM2 glycolysis signaling network could be targeted for the treatment of cancer caused by an aberrant RTK/PI3K/AKT/mTOR signaling pathway.
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              PKM2 Regulates the Warburg Effect and Promotes HMGB1 Release in Sepsis

              Increasing evidence suggests the important role of metabolic reprogramming in the regulation of the innate inflammatory response, but the underlying mechanism remains unclear. Here, we provide evidence to support a novel role for the pyruvate kinase M2 (PKM2)-mediated Warburg effect, namely aerobic glycolysis, in the regulation of high mobility group box 1 (HMGB1) release. PKM2 interacts with hypoxia-inducible factor 1α (HIF1α) and activates the HIF-1α-dependent transcription of enzymes necessary for aerobic glycolysis in macrophages. Knockdown of PKM2, HIF1α, and glycolysis-related genes uniformly decreases lactate production and HMGB1 release. Similarly, a potential PKM2 inhibitor, shikonin, reduces serum lactate and HMGB1 levels and protects mice from lethal endotoxemia and sepsis. Collectively, these findings shed light on a novel mechanism for metabolic control of inflammation by regulating HMGB1 release and highlight the importance of targeting aerobic glycolysis in the treatment of sepsis and other inflammatory diseases.
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                Author and article information

                Contributors
                fenghuang-zhan@uiowa.edu
                Journal
                J Hematol Oncol
                J Hematol Oncol
                Journal of Hematology & Oncology
                BioMed Central (London )
                1756-8722
                13 January 2017
                13 January 2017
                2017
                : 10
                : 17
                Affiliations
                [1 ]Department of Medicine, Division of Hematology, Oncology and Blood and Marrow Transplantation and Holden Comprehensive Cancer Center, University of Iowa, 585 Newton Rd, 52242 Iowa City, IA USA
                [2 ]Institute of Cancer Research, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
                Article
                392
                10.1186/s13045-017-0392-4
                5237262
                28086949
                d8595aa3-6933-468c-81b6-b11eddf80f66
                © The Author(s). 2017

                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.

                History
                : 23 November 2016
                : 3 January 2017
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/100000054, National Cancer Institute;
                Award ID: R01CA152105
                Award Recipient :
                Funded by: the Multiple Myeloma Research Foundation
                Funded by: FundRef http://dx.doi.org/10.13039/100003887, International Myeloma Foundation;
                Funded by: FundRef http://dx.doi.org/10.13039/100001422, American Society of Hematology;
                Funded by: FundRef http://dx.doi.org/10.13039/100005189, Leukemia and Lymphoma Society;
                Categories
                Research
                Custom metadata
                © The Author(s) 2017

                Oncology & Radiotherapy
                nek2,pyruvate kinase,multiple myeloma,alternative splicing
                Oncology & Radiotherapy
                nek2, pyruvate kinase, multiple myeloma, alternative splicing

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