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      Low Intensity and Frequency Pulsed Electromagnetic Fields Selectively Impair Breast Cancer Cell Viability

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          Abstract

          Introduction

          A common drawback of many anticancer therapies is non-specificity in action of killing. We investigated the potential of ultra-low intensity and frequency pulsed electromagnetic fields (PEMFs) to kill breast cancer cells. Our criteria to accept this technology as a potentially valid therapeutic approach were: 1) cytotoxicity to breast cancer cells and; 2) that the designed fields proved innocuous to healthy cell classes that would be exposed to the PEMFs during clinical treatment.

          Methods

          MCF7 breast cancer cells and their normal counterparts, MCF10 cells, were exposed to PEMFs and cytotoxic indices measured in order to design PEMF paradigms that best kill breast cancer cells. The PEMF parameters tested were: 1) frequencies ranging from 20 to 50 Hz; 2) intensities ranging from 2 mT to 5 mT and; 3) exposure durations ranging from 30 to 90 minutes per day for up to three days to determine the optimum parameters for selective cancer cell killing.

          Results

          We observed a discrete window of vulnerability of MCF7 cells to PEMFs of 20 Hz frequency, 3 mT magnitude and exposure duration of 60 minutes per day. The cell damage accrued in response to PEMFs increased with time and gained significance after three days of consecutive daily exposure. By contrast, the PEMFs parameters determined to be most cytotoxic to breast cancer MCF-7 cells were not damaging to normal MCF-10 cells.

          Conclusion

          Based on our data it appears that PEMF-based anticancer strategies may represent a new therapeutic approach to treat breast cancer without affecting normal tissues in a manner that is non-invasive and can be potentially combined with existing anti-cancer treatments.

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          Most cited references32

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          A novel assay for apoptosis. Flow cytometric detection of phosphatidylserine expression on early apoptotic cells using fluorescein labelled Annexin V.

          In the early stages of apoptosis changes occur at the cell surface, which until now have remained difficult to recognize. One of these plasma membrane alterations is the translocation of phosphatidylserine (PS) from the inner side of the plasma membrane to the outer layer, by which PS becomes exposed at the external surface of the cell. Annexin V is a Ca2+ dependent phospholipid-binding protein with high affinity for PS. Hence this protein can be used as a sensitive probe for PS exposure upon the cell membrane. Translocation of PS to the external cell surface is not unique to apoptosis, but occurs also during cell necrosis. The difference between these two forms of cell death is that during the initial stages of apoptosis the cell membrane remains intact, while at the very moment that necrosis occurs the cell membrane looses its integrity and becomes leaky. Therefore the measurement of Annexin V binding to the cell surface as indicative for apoptosis has to be performed in conjunction with a dye exclusion test to establish integrity of the cell membrane. This paper describes the results of such an assay, as obtained in cultured HSB-2 cells, rendered apoptotic by irradiation and in human lymphocytes, following dexamethasone treatment. Untreated and treated cells were evaluated for apoptosis by light microscopy, by measuring the amount of hypo-diploid cells using of DNA flow cytometry (FCM) and by DNA electrophoresis to establish whether or not DNA fragmentation had occurred. Annexin V binding was assessed using bivariate FCM, and cell staining was evaluated with fluorescein isothiocyanate (FITC)-labelled Annexin V (green fluorescence), simultaneously with dye exclusion of propidium iodide (PI) (negative for red fluorescence). The test described, discriminates intact cells (FITC-/PI-), apoptotic cells (FITC+/PI-) and necrotic cells (FITC+/PI+). In comparison with existing traditional tests the Annexin V assay is sensitive and easy to perform. The Annexin V assay offers the possibility of detecting early phases of apoptosis before the loss of cell membrane integrity and permits measurements of the kinetics of apoptotic death in relation to the cell cycle. More extensive FCM will allow discrimination between different cell subpopulations, that may or may not be involved in the apoptotic process.
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            Calcium and cancer: targeting Ca2+ transport.

            Ca2+ is a ubiquitous cellular signal. Altered expression of specific Ca2+ channels and pumps are characterizing features of some cancers. The ability of Ca2+ to regulate both cell death and proliferation, combined with the potential for pharmacological modulation, offers the opportunity for a set of new drug targets in cancer. However, the ubiquity of the Ca2+ signal is often mistakenly presumed to thwart the specific therapeutic targeting of proteins that transport Ca2+. This Review presents evidence to the contrary and addresses the question: which Ca2+ channels and pumps should be targeted?
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              Calcium orchestrates apoptosis.

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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2013
                11 September 2013
                : 8
                : 9
                : e72944
                Affiliations
                [1 ]Department of Environmental Science, University of Siena, Siena, Italy
                [2 ]Institute of Biomechanics, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
                [3 ]Electromagnetic Fields and Microwave Electronics Laboratory, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
                [4 ]Amphasys AG, Technopark Luzern, Root D4, Switzerland
                [5 ]The Center of Competence in Aerospace Biomedical Science and Technology, Lucerne University of Applied Sciences and Arts, Hergiswil, Switzerland
                [6 ]Department of Surgery, National University Hospital, Singapore, Singapore
                University of Chicago, United States of America
                Author notes

                Competing Interests: One of the authors, Grit Shade, is an employee of Amphasys, the company that provided the authors with the prototype of the Impedance Flow Cytometer utilized to conduct some of the experiments in the manuscript. GS provided technical support only. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

                Conceived and designed the experiments: AFO JF SC. Performed the experiments: SC. Analyzed the data: AFO SC. Contributed reagents/materials/analysis tools: ME JF GS. Wrote the paper: AFO SC CB. Realized PEMFs device and provided technical support: JF CB. Provided IFC instrument, technical support and help with analysis and interpretation of the IFC results: GS.

                Article
                PONE-D-12-38065
                10.1371/journal.pone.0072944
                3770670
                24039828
                821b3122-c063-4b9b-a8f2-b8e40aa60b5a
                Copyright @ 2013

                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.

                History
                : 27 November 2012
                : 22 July 2013
                Page count
                Pages: 13
                Funding
                This study was partially supported by the Swiss Federal Office of Public Health ( http://www.bag.admin.ch/) under the mandate number 11.003272, "Effects of pulsed electromagnetic fields on the proliferation of different mechano-sensitive cell types". The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding received for this study.
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