The authors performed a series of experiments to assess the response of heat shock protein 70 (hsp70) and regulator genes to electromagnetic fields (EMFs). Different cell types were used:

The authors exposed the cells to different EMFs. They used GSM signals at 1.71 GHz, but the modulation employed was either at a pulse repetition frequency of 217 Hz and a pulse width of 0.576 ms (GSM-217), or a signal simulating a typical conversation with 2, 8, and 217 Hz components (GSM-Talk). The time-averaged SAR for GSM-217 was between 1.5 and 2 W/kg, and that for GSM-Talk was 0.4 W/kg. The cells were exposed for either 6 or 48 hours.

The exposed cells (and control cells that were sham-exposed) were analyzed for growth regulatory genes, hsp70 levels, cardiac differentiation, and cell cycle phases.

Statistically significant changes were confined to the p53 -/- cells exposed to GSM-217 fields for 48 hours. A prominent increase of hsp70 levels was seen throughout the differentiation period, and was accompanied by early and transient increases of c-jun, p21, and c-myc genes. Cardiac differentiation and cell cycle phases were not affected.

The authors postulate that the genetic background of cells determine responses to GSM modulated EMFs. They also suggest that the different results obtained with GSM-Talk EMFs might be related to the lower SAR value. They point out that further research needs to be done to examine whether the observed changes would be short-term, or persist and result in sustained biological effects.