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      Metformin sensitizes the response of oral squamous cell carcinoma to cisplatin treatment through inhibition of NF-κB/HIF-1α signal axis

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          Abstract

          Resistance towards chemotherapy is a common complication in treatment of oral cancers, which leads to treatment failure and poor outcome. In recent years, a growing body of evidence has shown that tumour hypoxia significantly contributes to chemoresistance. Metformin, a widely used oral hypoglycaemic drug, can reportedly potentiate the efficacy of chemotherapeutic drugs in various cancers; however, the underlying mechanisms are intricate and have not been fully understood. In this study, we explored the role of metformin in chemosensitivity of oral squamous cell carcinoma cells (OSCC) to cisplatin both in vitro and in vivo, and attempted to elucidate its possible underlying mechanisms. Encouragingly, we found that metformin synergistically enhanced cisplatin cytotoxicity and reversed the chemoresistance to certain extent. This mechanism could likely be related with inhibition of the NF-κB/HIF-1α signal axis and lead to the downregulation of hypoxia-regulated genes products. Therefore, metformin could serve as a chemosensitiser for cisplatin-based regimens for OSCC, thereby providing a theoretical basis for future use in the treatment of oral cancers.

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          Global estimates of cancer prevalence for 27 sites in the adult population in 2008.

          Recent estimates of global cancer incidence and survival were used to update previous figures of limited duration prevalence to the year 2008. The number of patients with cancer diagnosed between 2004 and 2008 who were still alive at the end of 2008 in the adult population is described by world region, country and the human development index. The 5-year global cancer prevalence is estimated to be 28.8 million in 2008. Close to half of the prevalence burden is in areas of very high human development that comprise only one-sixth of the world's population. Breast cancer continues to be the most prevalent cancer in the vast majority of countries globally; cervix cancer is the most prevalent cancer in much of Sub-Saharan Africa and Southern Asia and prostate cancer dominates in North America, Oceania and Northern and Western Europe. Stomach cancer is the most prevalent cancer in Eastern Asia (including China); oral cancer ranks as the most prevalent cancer in Indian men and Kaposi sarcoma has the highest 5-year prevalence among men in 11 countries in Sub-Saharan Africa. The methods used to estimate point prevalence appears to give reasonable results at the global level. The figures highlight the need for long-term care targeted at managing patients with certain very frequently diagnosed cancer forms. To be of greater relevance to cancer planning, the estimation of other time-based measures of global prevalence is warranted. Copyright © 2012 UICC.
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            Therapeutic targeting of hypoxia and hypoxia-inducible factors in cancer.

            Insufficient tissue oxygenation, or hypoxia, contributes to tumor aggressiveness and has a profound impact on clinical outcomes in cancer patients. At decreased oxygen tensions, hypoxia-inducible factors (HIFs) 1 and 2 are stabilized and mediate a hypoxic response, primarily by acting as transcription factors. HIFs exert differential effects on tumor growth and affect important cancer hallmarks including cell proliferation, apoptosis, differentiation, vascularization/angiogenesis, genetic instability, tumor metabolism, tumor immune responses, and invasion and metastasis. As a consequence, HIFs mediate resistance to chemo- and radiotherapy and are associated with poor prognosis in cancer patients. Intriguingly, perivascular tumor cells can also express HIF-2α, thereby forming a "pseudohypoxic" phenotype that further contributes to tumor aggressiveness. Therefore, therapeutic targeting of HIFs in cancer has the potential to improve treatment efficacy. Different strategies to target hypoxic cancer cells and/or HIFs include hypoxia-activated prodrugs and inhibition of HIF dimerization, mRNA or protein expression, DNA binding capacity, and transcriptional activity. Here we review the functions of HIFs in the progression and treatment of malignant solid tumors. We also highlight how HIFs may be targeted to improve the management of patients with therapy-resistant and metastatic cancer.
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              Regulation of hypoxia-inducible factor-1α by NF-κB

              HIF (hypoxia-inducible factor) is the main transcription factor activated by low oxygen tensions. HIF-1α (and other α subunits) is tightly controlled mostly at the protein level, through the concerted action of a class of enzymes called PHDs (prolyl hydroxylases) 1, 2 and 3. Most of the knowledge of HIF derives from studies following hypoxic stress; however, HIF-1α stabilization is also found in non-hypoxic conditions through an unknown mechanism. In the present study, we demonstrate that NF-κB (nuclear factor κB) is a direct modulator of HIF-1α expression. The HIF-1α promoter is responsive to selective NF-κB subunits. siRNA (small interfering RNA) studies for individual NF-κB members revealed differential effects on HIF-1α mRNA levels, indicating that NF-κB can regulate basal HIF-1α expression. Finally, when endogenous NF-κB is induced by TNFα (tumour necrosis factor α) treatment, HIF-1α levels also change in an NF-κB-dependent manner. In conclusion, we find that NF-κB can regulate basal TNFα and, in certain circumstances, the hypoxia-induced HIF-1α.
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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                20 October 2016
                2016
                : 6
                : 35788
                Affiliations
                [1 ]Department of Oral and Maxillofacial Surgery, Nanjing Stomatological Hospital, Medical School of Nanjing University , No 30 Zhongyang Road, Nanjing, China
                [2 ]Central Laboratory of Stomatology, Nanjing Stomatological Hospital, Medical School of Nanjing University , Nanjing, P.R China
                [3 ]Department of Anesthesia, Nanjing Stomatological Hospital, Medical School of Nanjing University , Nanjing, P.R China
                Author notes
                [*]

                These authors contributed equally to this work.

                Article
                srep35788
                10.1038/srep35788
                5071902
                27762347
                aa4eea6c-e570-4828-bfe9-5a1b3a2d29c8
                Copyright © 2016, The Author(s)

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 04 July 2016
                : 05 October 2016
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