EMT and Stem Cell-Like Properties Associated with HIF-2α Are Involved in Arsenite-Induced Transformation of Human Bronchial Epithelial Cells

PLOS ONE, Dec 2019

Background Arsenic is well-established as a human carcinogen, but the molecular mechanisms leading to arsenic-induced carcinogenesis are complex and elusive. It is not been determined if the epithelial-mesenchymal transition (EMT) and stem cell-like properties contribute in causing to carcinogen-induced malignant transformation and subsequent tumor formation. Methods To investigate the molecular mechanisms underlying EMT and the emergence of cancer stem cell-like properties during neoplastic transformation of human bronchial epithelial (HBE) cells induced by chronic exposure to arsenite. HBE cells were continuously exposed to arsenite. Spheroid formation assays and analyses of side populations (SPs) were performed to confirm that arsenite induces the acquired EMT and cancer stem cell-like phenotype. Treated HBE cells were molecularly characterized by RT-PCR, Western blots, immunofluorescence, Southwestern assays, reporter assays, and chromatin immunoprecipitation. Results With chronic exposure to arsenite, HBE cells undergo an EMT and then acquire a malignant cancer stem cell-like phenotype. Twist1 and Bmi1 are involved in arsenite-induced EMT. The process is directly regulated by HIF-2α. The self-renewal genes, Oct4, Bmi1, and ALDH1, are necessary for arsenite-mediated maintenance of stem cells. Conclusions EMT, regulated by HIF-2α, and the development of a cancer stem cell-like phenotype are associated with arsenite-induced transformation of HBE cells.

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EMT and Stem Cell-Like Properties Associated with HIF-2α Are Involved in Arsenite-Induced Transformation of Human Bronchial Epithelial Cells

et al. (2012) EMT and Stem Cell-Like Properties Associated with HIF-2a Are Involved in Arsenite-Induced Transformation of Human Bronchial Epithelial Cells. PLoS ONE 7(5): e37765. doi:10.1371/journal.pone.0037765 EMT and Stem Cell-Like Properties Associated with HIF- 2a Are Involved in Arsenite-Induced Transformation of Human Bronchial Epithelial Cells Yuan Xu 0 Yuan Li 0 Ying Pang 0 Min Ling 0 Lu Shen 0 Xiaojun Yang 0 Jianping Zhang 0 Jianwei Zhou 0 Xinru Wang 0 Qizhan Liu 0 Surinder K. Batra, University of Nebraska Medical Center, United States of America 0 1 Institute of Toxicology, Nanjing Medical University , Nanjing , People's Republic of China, 2 The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University , Nanjing , People's Republic of China, 3 Department of General Surgery, The Second Affiliated Hospital, Nanjing Medical University , Nanjing , People's Republic of China Background: Arsenic is well-established as a human carcinogen, but the molecular mechanisms leading to arsenic-induced carcinogenesis are complex and elusive. It is not been determined if the epithelial-mesenchymal transition (EMT) and stem cell-like properties contribute in causing to carcinogen-induced malignant transformation and subsequent tumor formation. Methods: To investigate the molecular mechanisms underlying EMT and the emergence of cancer stem cell-like properties during neoplastic transformation of human bronchial epithelial (HBE) cells induced by chronic exposure to arsenite. HBE cells were continuously exposed to arsenite. Spheroid formation assays and analyses of side populations (SPs) were performed to confirm that arsenite induces the acquired EMT and cancer stem cell-like phenotype. Treated HBE cells were molecularly characterized by RT-PCR, Western blots, immunofluorescence, Southwestern assays, reporter assays, and chromatin immunoprecipitation. Results: With chronic exposure to arsenite, HBE cells undergo an EMT and then acquire a malignant cancer stem cell-like phenotype. Twist1 and Bmi1 are involved in arsenite-induced EMT. The process is directly regulated by HIF-2a. The selfrenewal genes, Oct4, Bmi1, and ALDH1, are necessary for arsenite-mediated maintenance of stem cells. Conclusions: EMT, regulated by HIF-2a, and the development of a cancer stem cell-like phenotype are associated with arsenite-induced transformation of HBE cells. - Funding: This work was supported by the Natural Science Foundations of China (30872146 and 81072327), Research Fund for the Doctoral Program of Higher Education of China (20103234110005), and Key Program of Educational Commission of Jiangsu Province of China (11KJA330002), a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (2010). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. . These authors contributed equally to this work. The epithelial-mesenchymal transition (EMT) is a developmental process by which epithelial cells are converted to mesenchymal cells during embryogenesis [1]. EMT, which involves loss of cell polarity, decreases in cell-to-cell adhesion, and increased capacity for migration, is necessary for tumor metastasis and organ fibrosis [2]. EMT, however, has not been considered to be involved in transformation of normal cells to malignant cells in the initiation of tumorigenesis [3]. A concept recently proposed to explain the characteristics of neoplastic tissues is the existence of self-renewing, stem-like cells within tumors, which have been called cancer stem cells (CSCs) [4]. Within a tumor, CSCs, which constitute a small portion of neoplastic cells, are defined by their capacity to produce new tumors. For this reason, they have also been termed tumorinitiating cells [5]. The process of EMT generates cells with stemlike properties [6]. The link between EMT and induction of cancer stem cells may explain why EMT induces tumor initiation and progression. Arsenic is well-established as a human carcinogen [7]. A positive correlation exists between arsenic exposure and increased incidences of various forms of cancer, as documented by reports from arsenic-endemic areas of the world [8]. To deal with this problem, it is essential to elucidate molecular mechanism involved in arsenic-induced carcinogenesis. Exposure to arsenic disrupts the dynamics of stem cells (SCs) in human and rodent skin in vivo and in vitro, resulting in an overabundance of stem cells/CSCs [9,10], an event likely involved in development of skin cancer. Arsenite apparently transforms prostate epithelial stem/progenitor cells into cancer stem-like cells that drive oncogenesis [11]. Arsenic affects human stem cells by blocking differentiation pathways, which are considered to be targets in carcinogenesis [12,13]. Chronic exposur (...truncated)


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Yuan Xu, Yuan Li, Ying Pang, Min Ling, Lu Shen, Xiaojun Yang, Jianping Zhang, Jianwei Zhou, Xinru Wang, Qizhan Liu. EMT and Stem Cell-Like Properties Associated with HIF-2α Are Involved in Arsenite-Induced Transformation of Human Bronchial Epithelial Cells, PLOS ONE, 2012, 5, DOI: 10.1371/journal.pone.0037765