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.
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.