en Cancer Biology Cancer Biology مقاله کامل Full Length/Original Article <p><strong>Background:</strong> Arsenic trioxide (ATO) has been reported as an effective anti-cancer and a US Food and Drug Administration (FDA) approved drug for treatment of some cancers. The aim of this study is to determine the underlying apoptosis molecular and cellular mechanisms of ATO in the presence or absence of ionizing radiation (IR) <em>in vitro</em> in the glioblastoma multiforme (GBM) cell line, U87MG. <strong>Methods:</strong> Cells were treated by different concentrations of ATO either in presence or absence of IR. Viability and apoptosis pathway of both treated and control groups were evaluated using MTT assay and the expression analysis of <em>Bax</em>, <em>Bcl-2</em>, and <em>caspase-3</em> genes, respectively. All treatments were performed on 100-&mu;m diameter spheroids. <strong>Results:</strong> Results showed a significant reduction in the survival of the cells in all treated groups. As expected, cell survival was much less in combination treatment than treatment with only ATO. Moreover, combination therapy made <em>Bax</em> and <em>caspase-3</em> up-regulated and <em>Bcl-2</em> down-regulated. <strong>Conclusion:</strong> ATO and radiation had a synergistic apoptotic effect on GBM cells by up-regulation of <em>caspase-3</em> and alteration of the <em>Bax</em>-<em>Bcl-2</em> balance; therefore, ATO may act as a potential anti-cancer agent against GBM cells through triggering the mitochondrial pathway of apoptosis.</p> Arsenic trioxide, Radiation, Apoptosis, Glioblastoma, Spheroids 330 337 http://ibj.pasteur.ac.ir/browse.php?a_code=A-10-1-658&slc_lang=en&sid=1 Kave Moloudi Yes Radiation Sciences Department, Faculty of allied Medicine school, Iran University of Medical Sciences, Tehran, Iran Ali Neshasteriz No Radiation biology research center, Iran University of medical sciences, Tehran, Iran Arshad Hosseini No Department of Medical Biotechnology, Faculty of allied Medicine, Iran University of Medical Sciences, Tehran, Iran Nazila Eyvazzadeh No Radiation Research Center, Faculty of Paramedicine, AJA University of Medical sciences, Tehran, Iran Mehdi Shomali No Radiology Department, Faculty of allied Medicine, Tehran University of Medical Sciences, Tehran, Iran Samira Eynali No Medical physics and Biomedical Engineering Department, school of Medicine, Tran University of Medical Sciences, Tehran, Iran Elahe Mirzaei No Microbiology Department, Faculty of Science, Islamic Azad University, Tehran, Iran Asaad Azarnezhad No Cellular & Molecular Research Center, Kurdistan University of Medical Sciences, Sanandaj, Iran