title: Antagonistic effects of a 50 Hz magnetic field and melatonin in the proliferation and differentiation of hepatocarcinoma cells.
abstract: OBJECTIVE
  Epidemiological and experimental evidence exists indicating that exposure to weak, extremely low frequency magnetic fields (ELF - MF) could affect cancer progression. It has been proposed that such hypothetical action could be mediated by MF-induced effects on the cellular response to melatonin (MEL), a potentially oncostatic neurohormone. The present study investigates the response of HepG2 cells to intermittent exposure to a 50 Hz, 10 µT MF, in the presence or absence of MEL at physiological (10 nM) or pharmacological doses (1 µM).
  
  
  METHODS
  The Trypan blue cell exclusion test, BrdU incorporation and PCNA expression assays were carried out to assess the cellular response in terms of viability and proliferation. In addition, albumin and alpha-fetoprotein, were analyzed as specific hepatocellular differentiation markers.
  
  
  RESULTS
  The results indicate that the MF exerts significant cytoproliferative and dedifferentiating effects that can be prevented by 10 nM MEL. Conversely, MEL exerts cytostatic and differentiating effects on HepG2 that are abolished by simultaneous exposure to MF.
  
  
  CONCLUSIONS
  As a whole, these results support the hypothesis that ELF - MF and MEL exert opposite, mutually counteracting effects on cell proliferation and differentiation.
authors.affiliation: Dept. Investigación-BEM, Hospital Ramón y Cajal-IRYCIS, Madrid, Spain. mariancid@yahoo.es
authors.forename: María Antonia
authors.initials: MA
authors.lastname: Cid
authors.forename: Alejandro
authors.initials: A
authors.lastname: Ubeda
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Hernández-Bule
authors.forename: María Antonia
authors.initials: MA
authors.lastname: Martínez
authors.forename: María Ángeles
authors.initials: MÁ
authors.lastname: Trillo
mesh_terms: D000418:Albumins / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival; D004261:DNA Replication; D056945:Hep G2 Cells; D006801:Humans; D060526:Magnetic Fields; D008550:Melatonin / Q000494:pharmacology* / Q000502:physiology; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D000509:alpha-Fetoproteins / Q000378:metabolism
chemical_list: D000418:Albumins; D000970:Antineoplastic Agents; D018809:Proliferating Cell Nuclear Antigen; D000509:alpha-Fetoproteins; D008550:Melatonin