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      Plumbagin induces G 2/M arrest, apoptosis, and autophagy via p38 MAPK- and PI3K/Akt/mTOR-mediated pathways in human tongue squamous cell carcinoma cells

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          Abstract

          Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone; PLB), a naturally occurring naphthoquinone isolated from the roots of Plumbaginaceae plants, has been reported to possess anticancer activities in both in vitro and in vivo studies, but the effect of PLB on tongue squamous cell carcinoma (TSCC) is not fully understood. This study aimed to investigate the effects of PLB on cell cycle distribution, apoptosis, and autophagy, and the underlying mechanisms in the human TSCC cell line SCC25. The results have revealed that PLB exerted potent inducing effects on cell cycle arrest, apoptosis, and autophagy in SCC25 cells. PLB arrested SCC25 cells at the G 2/M phase in a concentration- and time-dependent manner with a decrease in the expression level of cell division cycle protein 2 homolog (Cdc2) and cyclin B1 and increase in the expression level of p21 Waf1/Cip1, p27 Kip1, and p53 in SCC25 cells. PLB markedly induced apoptosis and autophagy in SCC25 cells. PLB decreased the expression of the anti-apoptotic proteins B-cell lymphoma 2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xl) while increasing the expression level of the pro-apoptotic protein Bcl-2-associated X protein (Bax) in SCC25 cells. Furthermore, PLB inhibited phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), glycogen synthase kinase 3β (GSK3β), and p38 mitogen-activated protein kinase (p38 MAPK) pathways as indicated by the alteration in the ratio of phosphorylation level over total protein expression level, contributing to the autophagy inducing effect. In addition, we found that wortmannin (a PI3K inhibitor) and SB202190 (a selective inhibitor of p38 MAPK) strikingly enhanced PLB-induced autophagy in SCC25 cells, suggesting the involvement of PI3K- and p38 MAPK-mediated signaling pathways. Moreover, PLB induced intracellular reactive oxygen species (ROS) generation and this effect was attenuated by l-glutathione (GSH) and n -acetyl- l-cysteine (NAC). Taken together, these results indicate that PLB promotes cellular apoptosis and autophagy in TSCC cells involving p38 MAPK- and PI3K/Akt/mTOR-mediated pathways with contribution from the GSK3β and ROS-mediated pathways.

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          Most cited references 48

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          Mitogen-activated protein kinases in innate immunity.

          Following pathogen infection or tissue damage, the stimulation of pattern recognition receptors on the cell surface and in the cytoplasm of innate immune cells activates members of each of the major mitogen-activated protein kinase (MAPK) subfamilies--the extracellular signal-regulated kinase (ERK), p38 and Jun N-terminal kinase (JNK) subfamilies. In conjunction with the activation of nuclear factor-κB and interferon-regulatory factor transcription factors, MAPK activation induces the expression of multiple genes that together regulate the inflammatory response. In this Review, we discuss our current knowledge about the regulation and the function of MAPKs in innate immunity, as well as the importance of negative feedback loops in limiting MAPK activity to prevent host tissue damage. We also examine how pathogens have evolved complex mechanisms to manipulate MAPK activation to increase their virulence. Finally, we consider the potential of the pharmacological targeting of MAPK pathways to treat autoimmune and inflammatory diseases.
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            Akt, FoxO and regulation of apoptosis.

            Forkhead box O (FoxO) transcription factors are downstream targets of the serine/threonine protein kinase B (PKB)/Akt. The Akt kinase regulates processes of cellular proliferation and survival. Phosphorylation of FoxOs by Akt inhibits transcriptional functions of FoxOs and contributes to cell survival, growth and proliferation. Emerging evidence suggests involvement of FoxOs in diverse intracellular signaling pathways with critical roles in a number of physiological as well as pathological conditions including cancer. The FoxO signaling is regulated by their interactions with other intracellular proteins as well as their post-translational modifications such as phosphorylation. FoxOs promote cell growth inhibitory and/or apoptosis signaling by either inducing expression of multiple pro-apoptotic members of the Bcl2-family of mitochondria-targeting proteins, stimulating expression of death receptor ligands such as Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), or enhancing levels of various cyclin-dependent kinase inhibitors (CDKIs). Coupled with their ability to cross-talk with p53, FoxOs represent an important class of tumor suppressors in a variety of cancers. This review summarizes our current understanding of mechanisms by which Akt and FoxOs regulate cell growth and survival that in turn offers opportunities for development of novel strategies to combat cancer. This article is part of a Special Issue entitled: P13K-AKT-FOxO axis in cancer and aging. 2011 Elsevier B.V. All rights reserved.
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              The p38 signalling transduction pathway, a Mitogen-activated protein (MAP) kinase pathway, plays an essential role in regulating many cellular processes including inflammation, cell differentiation, cell growth and death. Activation of p38 often through extracellular stimuli such as bacterial pathogens and cytokines, mediates signal transduction into the nucleus to turn on the responsive genes. p38 also transduces signals to other cellular components to execute different cellular responses. In this review, we summarize the characteristics of the major components of the p38 signalling transduction pathway and highlight the targets of this pathway and the physiological function of the p38 activation.
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                Author and article information

                Journal
                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                Drug Design, Development and Therapy
                Dove Medical Press
                1177-8881
                2015
                16 March 2015
                : 9
                : 1601-1626
                Affiliations
                [1 ]Department of Oral and Maxillofacial Surgery, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, People’s Republic of China
                [2 ]Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, FL, USA
                [3 ]Guizhou Provincial Key Laboratory for Regenerative Medicine, Stem Cell and Tissue Engineering Research Center and Sino–US Joint Laboratory for Medical Sciences, Guizhou Medical University, Guiyang, Guizhou, People’s Republic of China
                [4 ]Research Center for Bioengineering and Sensing Technology, University of Science and Technology Beijing, Beijing, People’s Republic of China
                [5 ]Department of Internal Medicine, University of Utah and Salt Lake Veterans Affairs Medical Center, Salt Lake City, UT, USA
                [6 ]Department of Colorectal Surgery, General Hospital of Ningxia Medical University, Yinchuan, Ningxia, People’s Republic of China
                [7 ]Cancer Center, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing, People’s Republic of China
                Author notes
                Correspondence: Shu-Feng Zhou, Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, 12901 Bruce B Downs Boulevard, Tampa, FL 33612, USA, Tel +1 813 974 6276, Fax +1 813 905 9885, Email szhou@ 123456health.usf.edu
                Jia-Xuan Qiu, Department of Oral and Maxillofacial Surgery, The First Affiliated Hospital of Nanchang University, 17 Yongwaizheng St, Nanchang 330006, Jiangxi, People’s Republic of China, Tel +86 791 8869 5069, Fax +86 791 8869 2745, Email qiujiaxuan@ 123456163.com
                Article
                dddt-9-1601
                10.2147/DDDT.S76057
                4365758
                © 2015 Pan et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

                The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

                Categories
                Original Research

                Pharmacology & Pharmaceutical medicine

                tscc, cell cycle, ros, p38 mapk, gsk3β

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