Differential gene expression in breast cancer cells exposed to low frequency magnetic fields

Objective: Recently we observed a decreased sensitivity of MCF-7 breast cancer cells to the frequently prescribed antiestrogenic drug tamoxifen when cells were exposed to low frequency electromagnetic fields (ELF-EMF). The behavior of the exposed cells bears similiarities to breast cancer cells with aquired tamoxifen resistance. To reveal the molecular basis of the altered growth characteristics gene expression in exposed cells was compared to the expression in non-exposed cells. Methods: MCF-7 cells were exposed to a 50Hz sinusoidal electromagnetic field of 1.2µT field intensity in a specially designed incubator for 48 hours. RNA was purified from exposed cells and from sham exposed control cells. cDNA of RNA was biotin-labeled by reverse transcription and subjected to microarray analysis on Human Breast Cancer and Estrogen Receptor Signalling Gene Array from SuperArray. Results: Of the 112 genes represented on the employed microarray at least 11 genes were differentially expressed in the MCF-7 cells exposed to 1,2µT. No gene repression by the magnetic field treatment could be observed. The expression of a tight junction associated protein and of the trefoil factor 1, pS2 was clearly increased. The expression of the other genes was increased to a lower extent. Among these genes were various proteases and two receptors for components of extracellular matrix. Among the differentially expressed genes only two genes were involved in receptor signalling. Conclusions: 1) Weak 50Hz electromagnetic fields modulate expression of several genes in breast cancer cells. 2) Most altered genes appear to be involved in metastatic processes. 3) There is no obvious link of the differentially expressed genes represented on the employed microarray to the phenomenon of tamoxifen resistance. 4) It is worthwhile to analyze to exposed cells for further sets of differentially expressed genes.

Eingereicht von: PD Dr. Rainer Girgert

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