FOCUS FORMATION OF C3H 10T1/2 COILS AND EXPOSURE TO A 836.55 MHZ MODULATED RADIOFREQUENCY FIELD/

Disruption of communication between transformed cells and normal cells is involved in tumor promotion. We have tested the hypothesis that ex posures to radiofrequency (RF) fields using a form of digital modulati on (TDMA) and a chemical tumor promoter, 12-O-tetradecanoylphorbol-13- acetate (TPA), are copromoters that enhance focus formation of transfo rmed cells in coculture with parental C3H/10T1/2 murine fibroblasts. R F field exposures did not influence TPA's dose-dependent promotion of focus formation in coculture. Cell cultures were exposed to an 836.55 MHz TDMA-modulated field in TEM transmission line chambers, with incid ent energies that simulated field intensities at a user's head. Specif ic absorption rates (SARs) of 0.15, 1.5, and 15 mu W/g were used durin g each digital packet, and the packet frequency was 50/s. The TEM cham bers were placed in a commercial incubator at 37 degrees C and 95% hum idity/5% CO2. The RF field exposures were in a repeating cycle, 20 min on, 20 min off, 24 h/day for 28 days. At 1.5 mu W/g, TPA-induced focu s formation (at 10, 30, and 50 ngl mi) was not significantly different in RF-exposed cultures compared to parallel sham-exposed cultures in ten independent experiments in terms of the number, density, and area of foci. Similarly, at 0.15 and 15.0 mu W/g, in two and four experimen ts, respectively, RF exposure did not alter TPA-induced focus formatio n. Tbe findings support a conclusion that repeated exposures to this R F held do not influence tumor promotion in vitro, based on the RF fiel d's inability to enhance TPA-induced focus formation. (C) 1997 Wiley-L iss, Inc.