Response of neuroblastoma cells to RF currents as a function of the signal frequency

Abstract

Background Capacitive-resistive electric transfer (CRET) is a non-invasive therapeutic strategy that applies radiofrequency electric currents within the 400–600 kHz range to tissue repair and regeneration. Previous studies by our group have shown that 48 h of intermittent exposure to a 570 kHz CRET signal at a subthermal density of 50 μA/mm 2 causes significant changes in the expression and activation of cell cycle control proteins, leading to cycle arrest in human cancer cell cultures. The present study investigates the relevance of the signal frequency in the response of the human neuroblastoma cell line NB69 to subthermal electric treatment with four different signal frequency currents within the 350–650 kHz range. Methods Trypan blue assay, flow cytometry, immunofluorescence and immunoblot were used to study the effects of subthermal CRET currents on cell viability, cell cycle progression and the expression of several marker proteins involved in NB69 cell death and proliferation. Results The results reveal that among the frequencies tested, only a 448 kHz signal elicited both proapoptotic and antiproliferative, statistically significant responses. The apoptotic effect would be due, at least in part, to significant changes induced by the 448 kHz signal in the expression of p53, Bax and caspase-3. The cytostatic response was preceded by alterations in the kinetics of the cell cycle and in the expression of proteins p-ERK1/2, cyclin D1 and p27, which is consistent with a potential involvement of the EGF receptor in electrically induced changes in the ERK1/2 pathway. This receives additional support from results indicating that the proapototic and antiproliferative responses to CRET can be transiently blocked when the electric stimulus is applied in the presence of PD98059, a chemical inhibitor of the ERK1/2 pathway. Conclusion The understanding of the mechanisms underlying the ability of slowing down cancer cell growth through electrically-induced changes in the expression of proteins involved in the control of cell proliferation and apoptosis might afford new insights in the field of oncology.

Effects of the signal modulation on the response of human fibroblasts to in vitro stimulation with subthermal RF currents

“…In sum, the results of this study, which are consistent with previously reported collagenogenic and cytoproliferative effects of electric stimulation with the nonmodulated CRET signal (Hernández-Bule et al 2019, 2017, reveal that subthermal CRET stimulation is also effective in promoting fibroblast proliferation, the modulated signal being more effective than the nonmodulated one in eliciting such response. Furthermore, although in the short term (4 h:10 min) both signals induce significant overexpression of the collagen-specific chaperone Hsp47, only the modulated signal induces significant activation and overexpression of Hsp27 in the same early phase, as well as decorin overexpression 20 hours later (24 hours after the exposure onset).…”

“…We have also reported that, as is the case for other RF electric and magnetic fields, the cellular response to CRET currents is non-linearly dependent on the frequency of the sinusoidal signal (Hernández-Bule et al 2019). The modulation of the carrier signal is another parameter that has been shown relevant, both in the bioeffects induced by RF electromagnetic fields (Barbault et al 2009;Blackman 2012;Juutilainen et al 2011) as in those elicited by RF electric currents such as those used by the electric scalpel when in modes cutting vs. coagulation (Karaki et al 2019).…”

Response of human cancer cells to simultaneous treatment with sorafenib and radiofrequency current

“…Subthermal CRET treatments can also exert anti-proliferative and/or cytotoxic effects in neuroblastoma and HCC cell lines through altering the expression of proteins involved in the MAPK/ERK1/2 signaling pathway ( 11 , 21 ). This pathway, when inhibited by sorafenib, restrains cell proliferation and induces apoptosis in HCC cells ( 17 , 25 ).…”

“…Indeed, our previous studies have revealed that electrical currents used in CRET therapies, when applied in vitro at subthermal densities, could induce significant effects on the proliferation ( 8 ), differentiation ( 9 , 10 ) or viability of different human cell types ( 1 ). These effects, which differ between distinct cell types and are non-linearly dependent on RF signaling parameters, such as frequency, modulation or current density, were found to be mediated by electrically-induced changes in the regulation of proteins involved in the aforementioned processes ( 11 , 12 ). In cancer cells, CRET currents have been shown to induce anti-proliferative and/or cytotoxic responses ( 11 , 13 – 15 ).…”

“…These effects, which differ between distinct cell types and are non-linearly dependent on RF signaling parameters, such as frequency, modulation or current density, were found to be mediated by electrically-induced changes in the regulation of proteins involved in the aforementioned processes ( 11 , 12 ). In cancer cells, CRET currents have been shown to induce anti-proliferative and/or cytotoxic responses ( 11 , 13 – 15 ).…”