Influence of a 50 Hz magnetic field and of all-trans‑retinol on the proliferation of human cancer cell lines

Abstract

Abstract. In vitro exposure to power frequency magnetic fields (MF) has been reported to influence cell proliferation and differentiation. However, the nature of the response of different human cancer cell types to these fields has not been sufficiently characterized. The present work investigates the response of two proliferating human cell lines of neuroblastoma (NB69) and hepatocarcinoma (HepG2) to a 42 h, intermittent treatment with a weak, 100 µT, 50 Hz MF, alone or in combination with 0.5 µM all-trans-retinol (ROL), a retinoid currently applied in oncostatic therapies. In each experimental replicate the cell samples were submitted to one of the following treatment combinations: MF+/ROL+, MF+/ ROL-, MF-/ROL+ or MF-/ROL-. The proliferative response was determined by cell counting (Trypan blue exclusion), BrdU incorporation and by spectrophotometric analysis of total protein and DNA content. The results show that when administered separately, the two treatments, MF and ROL, significantly enhanced cell proliferation in both cell lines. In NB69 simultaneous administration of MF and ROL induced an additive effect on cell proliferation, associated to increased DNA content. By contrast, in HepG2 the ROL-induced cell proliferation and increased protein content were partially blocked by simultaneous exposure to MF. Taken together, these data show that both agents, a weak MF and ROL at a low concentration, induce proliferative responses in the two assayed human cell lines. However, significant differences were observed between the responses of the two cellular species to the combined treatment with ROL and MF, indicating that the mechanisms underlying the cellular response to each of the two agents can mutually interact in a manner that is cell type-specific.

The Proliferative Response of NB69 Human Neuroblastoma Cells to a 50 Hz Magnetic Field is mediated by ERK1/2 Signaling

“…At 42 hours of intermittent exposure, a significant increase was observed in the percent of cells in S-phase, of DNA synthesis, which is consistent with the increase in the cell number obtained 21 hours later, at the end of the 63-hour exposure period. These data confirm previous results from our group [32][33][34] and highlight the importance of intermittency in the functional changes induced by weak ELF-MF in cellular biosystems. The intermittent treatment also induced early, transient and cyclic activation of ERK1/2, which peaked at the "On" intervals of field exposure.…”

“…Previous data by our group indicate that intermittent exposure to a 50 Hz, 100 µT MF could enhance proliferation in NB69 cells from a human neuroblastoma [32][33][34]. The present study was addressed to confirm and characterize such a proliferative response, and investigate the signaling events involved in it.…”

“…Two types of intermittence were tested, 5 min On/10 min Off or 3 h On/3 h Off. Both intermittence patterns had been shown to affect different biological systems in vitro [19,23,32,34]. All procedures and analysis were conducted blindly for experimental conditions.…”

“…The MF exposure set-up has been described elsewhere by Trillo et al, [34]. The MF was created by a wave generator Newtronic Model 200MSTPC (Madrid, Spain) connected to pairs of coils set in a Helmholtz configuration.…”

Antagonistic Effects of a 50 Hz Magnetic Field and Melatonin in the Proliferation and Differentiation of Hepatocarcinoma Cells

“…The exposure set-up has been described before by Trillo et al [12]. Briefly, the system consists of a function generator (Newtronics Model 200MSTPC, Madrid, Spain) and an ammeter (Hewlett Packard, model 974A, Loveland, CO, USA), connected in series to two identical pairs of coils.…”