title: Transient suppression of X-ray-induced apoptosis by exposure to power frequency magnetic fields in MCF-7 cells.
abstract: Epidemiological studies suggest that exposure to power frequency magnetic fields may be a risk factor for breast cancer in humans. To study the relationship between exposure to 60-Hz magnetic fields (MFs) and breast cancer, cell cycle distribution, apoptosis, and the expression of related proteins (p21, Bax, and Bcl-2) were determined in MCF-7 cells following exposure to magnetic fields (60 Hz, 5 mT) alone or in combination with X rays. It was found that exposure of MCF-7 cells to 60-Hz MFs for 4, 8, and 24 h had no effect on cell cycle distribution. Furthermore, 60-Hz MFs failed to affect cell growth arrest and p21 expression induced by X rays (4 Gy). Similarly, 60-Hz MFs did not induce apoptosis or the expression of Bax and Bcl-2, two proteins related to apoptosis. However, exposure of cells to 60-Hz MFs for 24 h after irradiation by X rays (12 Gy) significantly decreased apoptosis and Bax expression but increased Bcl-2 expression. The effects of exposure to 60-Hz MFs on X-ray-induced apoptosis and Bax and Bcl-2 expressions were not observed at 72 h. These data suggest that exposure to 60-Hz MFs has no effects on the growth of MCF-7 cells, but it might transiently suppress X-ray-induced apoptosis through increasing the Bcl-2/Bax ratio.
authors.affiliation: Department of Radiation Medicine, Fourth Military Medical University, Xi'an, 710032, China.
authors.forename: G R
authors.initials: GR
authors.lastname: Ding
authors.forename: T
authors.initials: T
authors.lastname: Nakahara
authors.forename: F R
authors.initials: FR
authors.lastname: Tian
authors.forename: Y
authors.initials: Y
authors.lastname: Guo
authors.forename: J
authors.initials: J
authors.lastname: Miyakoshi
mesh_terms: D017209:Apoptosis / Q000528:radiation effects; D015153:Blotting, Western; D002453:Cell Cycle / Q000528:radiation effects; D004574:Electromagnetic Fields; D005434:Flow Cytometry; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014965:X-Rays; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)