title: Focus formation of C3H/10T1/2 cells and exposure to a 836.55 MHz modulated radiofrequency field.
abstract: Disruption of communication between transformed cells and normal cells is involved in tumor promotion. We have tested the hypothesis that exposures to radiofrequency (RF) fields using a form of digital modulation (TDMA) and a chemical tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), are copromoters that enhance focus formation of transformed cells in coculture with parental C3H/10T1/2 murine fibroblasts. RF 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 incident energies that simulated field intensities at a user's head. Specific absorption rates (SARs) of 0.15, 1.5, and 15 muW/g were used during each digital packet, and the packet frequency was 50/s. The TEM chambers were placed in a commercial incubator at 37 degrees C and 95% humidity/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 muW/g, TPA-induced focus formation (at 10, 30, and 50 ng/ml) 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 muW/g, in two and four experiments, respectively, RF exposure did not alter TPA-induced focus formation. The findings support a conclusion that repeated exposures to this RF field do not influence tumor promotion in vitro, based on the RF field's inability to enhance TPA-induced focus formation.
authors.affiliation: Jerry L. Pettis Memorial Veterans Administration Medical Center, Loma Linda, California 92357, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Cain
authors.forename: D L
authors.initials: DL
authors.lastname: Thomas
authors.forename: W R
authors.initials: WR
authors.lastname: Adey
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002273:Carcinogens / Q000633:toxicity; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D004574:Electromagnetic Fields; D005347:Fibroblasts; D051379:Mice; D008809:Mice, Inbred C3H; D018715:Microscopy, Video; D011846:Radio Waves; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity
chemical_list: D002273:Carcinogens; D013755:Tetradecanoylphorbol Acetate