Medical/biological study (experimental study)

Electromagnetic fields alter the expression of estrogen receptor cofactors in breast cancer cells med./bio.

By: Girgert R, Gründker C, Emons G, Hanf V

Published in: Bioelectromagnetics 2008; 29 (3): 169-176

Aim of study (acc. to author)

This in vitro study should analyze the changes in expression of cofactors of the estrogen receptors in human breast cancer cells exposed to low frequency electromagnetic fields.

Background/further details

In previous studies (see publication 1254, publication 5621) a decrease in efficacy of the selective estrogen receptor modulator tamoxifen was observed in breast cancer cells exposed to electromagnetic fields. Tamoxifen is applied in estrogen receptor positive breast cancer therapy as it binds to estrogen receptors of breast cancer cells and through this prevents their proliferation. As estrogen receptors can be modified by cofactors, gene expression of these cofactors (coactivator: AIB1, SRC-1, corepressor: N-Cor, SMRT) should be elucidated. It is reported that in tumors which express higher amounts of coactivators and less corepressors tamoxifen induces proliferation of the breast cancer cells and significantly reduces the disease-free survival.

Endpoint

molecular biosynthesis: expression of estrogen receptor cofactors

Exposure

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: continuous for 24 h up to 96 h	magnetic flux density: 1.2 µT

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	continuous for 24 h up to 96 h

Exposure setup

Exposure source	coil(s)
Setup	75 cm long copper tube with a diameter of 30 cm, closed at both ends by a copper plate, copper wire wound round the tube and connected to a signal generator, for stabilization of magnetic field small sensor coil in the center of the tube
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.2 µT	-	-	-	-

Reference articles

Girgert R et al. (2005): Induction of tamoxifen resistance in breast cancer cells by ELF electromagnetic fields

Exposed system:

intact cell/cell culture
MCF-7 (breast cancer cell line, p40 and p181 clone)

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: gene expression (microarray analysis, RT-PCR), protein expression of estrogen receptor cofactors (Western Blot, densitometry)

Investigated system:

DNA/RNA

Investigated organ system:

breast

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The gene expression of both coactivators were more strongly expressed in the exposed breast cancer cells while the gene expression of the two corepressors decreased. The RNA analysis was confirmed by protein analysis.
The observed increased estrogen receptor coactivators expression and decreased estrogen receptor corepressors can explain the decrease in efficacy of tamoxifen during exposure to electromagnetic fields.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit (Federal Ministry of the Environment, Nature Conservation, and Nuclear Safety), Germany

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