Forschungsgemeinschaft Funk e.V.

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Edition No. 1, November 1995
Growth behaviour of human leukemia HL-60 cells influenced by high frequency electromagnetic fields for the investigation of cancer promoting effects

Dr. med R. Fitzner, E. Langer , Dipl.-Ing. E. Zemann, Institut für Klinische Chemie und Klinische Biochemie der Freien Universität Berlin, Hindenburgdamm 30, D-12200 Berlin

For quite some time now, the question has been discussed of wether electromagnetic fields may cause or promote cancer. The cancerogenic effect of agents is that they either initiate tumors or promote tumors. Initiation of tumors means a transformation of normal cells into melignant tumor cells, i.e. a change in the genetic factors of the cell, whereas tumor promotion describes the augmentative effects in transformed cells, which characterize the propagation tendency, the degree of malignity of the tumor und thus its aggressive potential.

Through numerous in-vitro-investigations using animal and human tumor cells already transformed, we were able to prove that not additional promotion of these cells was caused by being exposed to 50 Hz magnetic fields.

This study deals with the results of in-vitro-tests of human leukemia HL-60 cells in suspension cultures exposed to high frequency electromagnetic fields of 1.8 GHz pulsed with 217 Hz and 900 MHz pulsed with 217 Hz. The question is wether an additional promotion of growth of transformed human tumor cells and because of this a cancerogenic effect can be proved. As critical analytical indicators of the growth speed of leukemia cells the doubling time and the synthesis and release of the enzyme thymidine kinase (TK) have been determined. Cells exposed to electromagnetic fields are compared with identical controls not exposed to high frequency fields. A provable effect would lead to a multiple acceleration of cell division and to the generation and release of thymidine kinase in suspension cultures.

Biochemically, thymidine kinase is an intracellular enzyme which catalyses the phosphorylation of thymidine into thymidine monophosphate. Thymidine triphosphate generated from thymidine monophosphate ist used for the DNA synthesis in cells. In high-differentiated tissues with terminated cell proliferation (for instance kidney parenchyma, nerve tissue) the thymidine kinase activity is only low. The extracellular serum activity is low with healthy adults. With patients with proliferative malignomas (for instance myeloic or lymphoblastic leukemia, but also solid tumors like small-cell-type lung carcinomas, mamacarcinomas and brain tumors) serum activity is significantly higher.

The experimental equipment consists of a GTEM-cell, model 5302, made by EMCO, USA, a signal generator, type SMT 03, by Rhode & Schwarz, Germany, and band amplifiers for the frequency range of 900 MHz and 1.8 GHz. A thermostat maintains a constant temperature of 37 °C ± 0.1 °C. The samples are exposed to high frequency electromagnetic fields for 8 and 24 hours. For the in vitro tests, cells of human leukemia origin HL-60 were used. The cells were cultered in RPMI 1640 medium. To determine thymidine kinase activity in the cell culture supernatant a radio enzyme assay is employed.

Already transformed human white blood cells (leukemia cells), which were exposed to high frequency fields (900 MHz and 1.8 GHz, pulsed with 217 Hz) show no multiple increase in growth speed compared with identical control cells not exposed, because doubling time and thymidine kinase activity, measured in the cell culture supernatants, do not differ essentially from each other.

Due to the test results based on the parameters doubling time and thymidine kinase activity, an additional promotion of human leukemia cells exposed to high frequency fields of 900 MHz and 1.8 GHz, pulsed with 217 Hz, can be excluded. Based on these investigations, which simulated electromagnetic field conditions as they exist in digital mobile telephone networks, a cancerogenic effect of electromagnetic fields can therefore not be determined.

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