Effects of extremely low-frequency pulsed electromagnetic fields (ELF-PEMFs) on glioblastoma cells (U87)

Abstract

The impact of extremely low-frequency pulsed electromagnetic fields (ELF-PEMFs) at various frequencies and amplitudes was investigated on cell cycle, apoptosis and viability of the Glioblastoma Multiforme (GBM) cell line (U87), in vitro. The GBM is a malignant brain tumor with high mortality in humans and poorly responsive to the most common type of cancer treatments, such as surgery, chemotherapy and radiation therapy. U87 cells with five experimental groups (I-V) were exposed to various ELF-PEMFs for 2, 4 and 24 h, as follows: (I) no exposure, control; (II) 50 Hz 100 ± 15 G; (III) 100 Hz 100 ± 15 G; (IV) 10 Hz 50 ± 10 G; (V) 50 Hz 50 ± 10 G. The morphology properties, cell viability and gene expression of proteins involved in cell cycle regulation (Cyclin-D1 and P53) and apoptosis (Caspase-3) were investigated. After 24 h, the cell viability and Cyclin-D1 expression increased in Group II (30%, 45%), whereas they decreased in Groups III (29%, 31%) and IV (21%, 34%); P53 and Caspase-3 elevated only in Group III; and no significant difference was observed in Group V, respectively, compared with the control (p < 0.05). The data suggest that the proliferation and apoptosis of human GBM are influenced by exposure to ELF-PEMFs in different time-dependent frequencies and amplitudes. The fact that some of the ELF-PEMFs frequencies and amplitudes favor U87 cells proliferation indicates precaution for the use of medical devices related to the MFs on cancer patients. On the other hand, some other ELF-PEMFs frequencies and intensities arresting U87 cells growth could open the way to develop novel therapeutic approaches.

Comparative Analysis of Biological Effects Induced on Different Cell Types by Magnetic Fields with Magnetic Flux Densities in the Range of 1–60 mT and Frequencies up to 50 Hz

“…Incidence on Cell Shape, Cytoskeleton, Cell Adhesion and Differentiation MF exposure can modify the shape of different cell types. These shape changes, which involve the whole cell or specialized components of it, depend on the kind of MF, on the cell type considered, as well as on their corresponding mode of growth [7,11,12,16,19,27,31,32]. For example, PBLs lose their round shape and became irregularly elongated [11], whereas the surface microvilli of U937 cells, which are commonly few and short, become abundant and lamellar-shaped under exposure conditions, i.e., after 24 h exposure to a SMF of 6 mT [11,16,32].…”

“…Control HaCaT cells have typical polygonal epithelial morphology, while 96 h exposed cells (2 mT, 50 Hz, ELF-EMF) appear in totally confluent monolayers [31]. A 24 h exposure to a 10 Hz, 5 mT, ELF-PMF induces significant morphological changes in U87 cells, mainly including processes and soma alteration, decreased body mass, and increased cell surface, shortening of the processes, shrinkage/swelling of the soma, and apoptotic-like cell morphologies (surface blebs, pyknotic nucleus) [7]. Microvilli are mainly composed of cytoskeletal components.…”

“…Increases of 30% and 45% were instead found when the same cells were exposed, again for 24 h, to a 10 mT, 50 Hz, ELF-PMF. The protein p53 was downregulated in both exposure conditions, with lower levels of expression as the B and f values increase [7]. Cyclin-D1 is involved in regulating the cell cycle progression, and drives the G1/S phase transition [35], whereas the "guardian of the genome", p53, is an enzyme that plays a central role during the execution of apoptosis [36].…”

“…• type of MF, i.e., static or time-varying; therefore, also the magnetic flux density (B) and oscillation frequency (f ) must be taken into account [3][4][5][6][7]; • type of biological target, from molecules to a whole organism, by including constitutive differences between in vitro and in vivo model systems. For instance, the MF induced inside the human body depends on the anatomy of the exposed person, e.g., height, posture, body mass index (BMI).…”

“…The maximum possible exposure near a specific source often differs by some orders of magnitude from the average individual exposure of a person. For example, at 5 cm from a vacuum cleaner, B is of about 40 µT, but at 1 m it will be around 0.2 µT [9,10]; • alternation and duration of exposure [5][6][7][11][12][13].…”