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MicroRNA-25 regulates chemoresistance-associated autophagy in breast cancer cells, a process modulated by the natural autophagy inducer isoliquiritigenin

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      Abstract

      Recent findings have revealed that dysregulated miRNAs contribute significantly to autophagy and chemoresistance. Pharmacologically targeting autophagy-related miRNAs is a novel strategy to reverse drug resistance. Here, we report a novel function of isoliquiritigenin (ISL) as a natural inhibitor of autophagy-related miR-25 in killing drug-resistant breast cancer cells. ISL induced chemosensitization, cell cycle arrest and autophagy, but not apoptosis, in MCF-7/ADR cells. ISL also promoted the degradation of the ATP-binding cassette (ABC) protein ABCG2 primarily via the autophagy-lysosome pathway. More importantly, miRNA 3.0 array experiments identified miR-25 as the main target of ISL in triggering autophagy flux. A mechanistic study validated that miR-25 inhibition led to autophagic cell death by directly increasing ULK1 expression, an early regulator in the autophagy induction phase. miR-25 overexpression was demonstrated to block ISL-induced autophagy and chemosensitization. Subsequent in vivo experiments showed that ISL had chemosensitizing potency, as revealed by an increase in LC3-II staining, the downregulation of ABCG2, a reduction in miR-25 expression and the activation of the miR-25 target ULK1. Overall, our results not only indicate that ISL acts as a natural autophagy inducer to increase breast cancer chemosensitivity, but also reveal that miR-25 functions as a novel regulator of autophagy by targeting ULK1.

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      Most cited references 51

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      Effective treatment of metastatic cancers usually requires the use of toxic chemotherapy. In most cases, multiple drugs are used, as resistance to single agents occurs almost universally. For this reason, elucidation of mechanisms that confer simultaneous resistance to different drugs with different targets and chemical structures - multidrug resistance - has been a major goal of cancer biologists during the past 35 years. Here, we review the most common of these mechanisms, one that relies on drug efflux from cancer cells mediated by ATP-binding cassette (ABC) transporters. We describe various approaches to combating multidrug-resistant cancer, including the development of drugs that engage, evade or exploit efflux by ABC transporters.
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        In this article, the American Cancer Society provides an overview of female breast cancer statistics in the United States, including data on incidence, mortality, survival, and screening. Approximately 232,340 new cases of invasive breast cancer and 39,620 breast cancer deaths are expected to occur among US women in 2013. One in 8 women in the United States will develop breast cancer in her lifetime. Breast cancer incidence rates increased slightly among African American women; decreased among Hispanic women; and were stable among whites, Asian Americans/Pacific Islanders, and American Indians/Alaska Natives from 2006 to 2010. Historically, white women have had the highest breast cancer incidence rates among women aged 40 years and older; however, incidence rates are converging among white and African American women, particularly among women aged 50 years to 59 years. Incidence rates increased for estrogen receptor-positive breast cancers in the youngest white women, Hispanic women aged 60 years to 69 years, and all but the oldest African American women. In contrast, estrogen receptor-negative breast cancers declined among most age and racial/ethnic groups. These divergent trends may reflect etiologic heterogeneity and the differing effects of some factors, such as obesity and parity, on risk by tumor subtype. Since 1990, breast cancer death rates have dropped by 34% and this decrease was evident in all racial/ethnic groups except American Indians/Alaska Natives. Nevertheless, survival disparities persist by race/ethnicity, with African American women having the poorest breast cancer survival of any racial/ethnic group. Continued progress in the control of breast cancer will require sustained and increased efforts to provide high-quality screening, diagnosis, and treatment to all segments of the population. © 2013 American Cancer Society, Inc.
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          Mammalian autophagy: core molecular machinery and signaling regulation.

          Autophagy, a cellular catabolic pathway, is evolutionarily conserved from yeast to mammals. Central to this process is the formation of autophagosomes, double-membrane vesicles responsible for delivering long-lived proteins and excess or damaged organelle into the lysosome for degradation and reuse of the resulting macromolecules. In addition to the hallmark discovery of core molecular machinery components involved in autophagosome formation, complex signaling cascades controlling autophagy have also begun to emerge, with mTOR as a central but far from exclusive player. Malfunction of autophagy has been linked to a wide range of human pathologies, including cancer, neurodegeneration, and pathogen infection. Here we highlight the recent advances in identifying and understanding the core molecular machinery and signaling pathways that are involved in mammalian autophagy. Copyright 2009 Elsevier Ltd. All rights reserved.
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            Author and article information

            Affiliations
            1 Department of Mammary Disease, Guangdong Provincial Hospital of Chinese Medicine
            2 School of Chinese Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China
            3 Department of Dermatology, Guangdong Provincial Hospital of Chinese Medicine, The Second Clinical Collage of Guangzhou University of Chinese Medicine
            4 Deapartment of Pharmacology, Chengdu University of Traditional Chinese Medicine
            Author notes
            Correspondence to: Jianping Chen, jpjpchen@ 123456yahoo.com
            Journal
            Oncotarget
            Oncotarget
            ImpactJ
            Oncotarget
            Impact Journals LLC
            1949-2553
            August 2014
            9 July 2014
            : 5
            : 16
            : 7013-7026
            25026296
            4196180
            Copyright: © 2014 Wang et al.

            This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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