Medical/biological study (experimental study)

ERK1/2 phosphorylation, induced by electromagnetic fields, diminishes during neoplastic transformation med./bio.

By: Jin M, Blank M, Goodman R

Published in: J Cell Biochem 2000; 78 (3): 371-379

Aim of study (acc. to author)

The question whether an extremely low frequency electromagnetic field can act as co-promoter during neoplastic transformation should be clarified in mouse cells in vitro.

Background/further details

The cell line used could be modified in its transformation status. Adding of retinyl acetate leads to suppression of the cell transformation thus affording the cell examination at three stages: 1. before initiation of transformation, 2. early in the transformation, and 3. at full of transformation.
TPA treated cells were used as positive control.

Endpoint

cell transformation: co-promoter effect (oncogene/Hsp levels, signal pathways, AP-1 activation)

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: up to 180 min continuous	electric field strength: 11 µV/m (for 8µT) magnetic flux density: 300 µT maximum (0.8, 8, 80, 300 µT)

General information

Cells were exposed: i) during suppression of neoplastic phenotype ii) 4 days after withdrawal of RAC iii) during full neoplastic transformation

Exposure 1

Main characteristics

Frequency	60 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	up to 180 min continuous

Exposure setup

Exposure source	Helmholtz coils
Chamber	100 mm Petri dishes on Plexiglas stand, horizontal orientation
Setup	coils consisting of 164 turns of 19-gauge wire on a square form (13 cm long, 14 cm wide) with 8 cm spacing; coils shielded in µ-metal containers
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
electric field strength	11 µV/m	-	calculated	-	for 8µT
magnetic flux density	300 µT	maximum	measured	-	0.8, 8, 80, 300 µT

Exposed system:

intact cell/cell culture
INITC3H 10T1/2 cells (derived from mouse embryo fibroblasts, transformed carcinogenically by methylcholanthrene, resulting neoplastic phenotype can be suppressed by the presence of retinyl acetate)

Methods Endpoint/measurement parameters/methodology

cell transformation: oncogene/Hsp levels (c-Fos/Hsp70 level; phosphor imager), signal pathway (phosphorylation of mitogen activated protein kinase (MAPK)/stress activated protein kinase (SAPK); Western blot, phosphor imager), AP-1 DNA binding activation (EMSA)
cell viability/cell division/proliferation: general cell health (trypan blue staining, light microscopy)

Investigated system:

isolated bio./chem. substance
intact cell/cell culture

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

The exposure to electromagnetic field induced significant increases in Hsp70, c-Fos levels and in AP-1 DNA binding activation in non-transformed cells (stage 1). These effects reduced in transformed cells.
Phosphorylation of mitogen-activated protein kinase was most pronounced before the onset of transformation, but this increase diminished during the transformation process. No changes in phosphorylation of the stress-activated protein kinase was detected in cells exposed to electromagnetic fields at any transformation stage.
The results of the examined parameters indicate that electromagnetic fields did not affect the cell transformation rate or acted as a co-promoter.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Robert I. Goodman Fund

Martínez MA et al. (2019): Involvement of the EGF Receptor in MAPK Signaling Activation by a 50 Hz Magnetic Field in Human Neuroblastoma Cells
Martinez MA et al. (2012): The Proliferative Response of NB69 Human Neuroblastoma Cells to a 50 Hz Magnetic Field is mediated by ERK1/2 Signaling
Lee HJ et al. (2012): Combined effects of 60 Hz electromagnetic field exposure with various stress factors on cellular transformation in NIH3T3 cells
Mannerling AC et al. (2010): Effects of 50-Hz magnetic field exposure on superoxide radical anion formation and HSP70 induction in human K562 cells
Goodman R et al. (2009): Extremely low frequency electromagnetic fields activate the ERK cascade, increase hsp70 protein levels and promote regeneration in Planaria
Friedman J et al. (2007): Mechanism of short-term ERK activation by electromagnetic fields at mobile phone frequencies
Sun WJ et al. (2001): Exposure to 50 Hz electromagnetic fields induces the phosphorylation and activity of stress-activated protein kinase in cultured cells
Miyakoshi J et al. (2000): Exposure to extremely low frequency magnetic fields suppresses x-ray-induced transformation in mouse C3H10T1/2 cells
Lin H et al. (1998): Magnetic field activation of protein-DNA binding
Goodman R et al. (1998): Magnetic field stress induces expression of hsp70
Lin H et al. (1998): Myc-mediated transactivation of HSP70 expression following exposure to magnetic fields
Saffer JD et al. (1997): Power frequency magnetic fields do not contribute to transformation of JB6 cells
Rao S et al. (1996): Regulation of c-fos is affected by electromagnetic fields
Balcer-Kubiczek EK et al. (1996): Rodent cell transformation and immediate early gene expression following 60-Hz magnetic field exposure
Goodman R et al. (1994): Increased levels of hsp70 transcripts induced when cells are exposed to low frequency electromagnetic fields
Phillips JL et al. (1992): Magnetic field-induced changes in specific gene transcription