Magnetic Fields and Cancer: Epidemiology, Cellular Biology, and Theranostics

Bron: www.mdpi.com/1422-0067/23/3/1339/htm
Int. J. Mol. Sci. 2022, 23(3), 1339; doi.org/10.3390/ijms23031339

by Massimo E. Maffei
Department Life Sciences and Systems Biology, University of Turin, Via Quarello 15/a, 10135 Turin, Italy

Received: 30 December 2021 / Revised: 22 January 2022 / Accepted: 22 January 2022 / Published: 25 January 2022
(This article belongs to the Special Issue The Effect of Magnetic Fields on Living Organisms: Biomolecular and Cellular Mechanisms)

Abstract
Humans are exposed to a complex mix of man-made electric and magnetic fields (MFs) at many different frequencies, at home and at work. Epidemiological studies indicate that there is a positive relationship between residential/domestic and occupational exposure to extremely low frequency electromagnetic fields and some types of cancer, although some other studies indicate no relationship. In this review, after an introduction on the MF definition and a description of natural/anthropogenic sources, the epidemiology of residential/domestic and occupational exposure to MFs and cancer is reviewed, with reference to leukemia, brain, and breast cancer. The in vivo and in vitro effects of MFs on cancer are reviewed considering both human and animal cells, with particular reference to the involvement of reactive oxygen species (ROS). MF application on cancer diagnostic and therapy (theranostic) are also reviewed by describing the use of different magnetic resonance imaging (MRI) applications for the detection of several cancers. Finally, the use of magnetic nanoparticles is described in terms of treatment of cancer by nanomedical applications for the precise delivery of anticancer drugs, nanosurgery by magnetomechanic methods, and selective killing of cancer cells by magnetic hyperthermia. The supplementary tables provide quantitative data and methodologies in epidemiological and cell biology studies. Although scientists do not generally agree that there is a cause-effect relationship between exposure to MF and cancer, MFs might not be the direct cause of cancer but may contribute to produce ROS and generate oxidative stress, which could trigger or enhance the expression of oncogenes.

Keywords: magnetic field; cancer; epidemiology; therapy; diagnostics; theranostic; MRI; magnetic nanoparticles; nanomedicine; reactive oxygen species


5. Conclusions
The potential health effects of man-made EMF have been a topic of scientific interest since the late 1800s and have received particular attention during the last 40 years. Since the first studies suggesting a relationship between MF and childhood cancer 29, the scientific community has evaluated the possible mechanisms for the effects of MFs on biological systems. Epidemiological studies are often controversial and sometimes misleading. Nevertheless, there is a consensus on the positive relationship between residential/domestic exposure to ELF EMF and the occurrence of brain cancer, whereas contrasting results require more experimentation to assess the influence of occupational exposure to MFs on brain cancer. The epidemiology of leukemia as related to ELF EMF in adults is controversial in both residential/domestic and occupational exposure. For children, leukemia is not associated to occupational exposure, whereas a growing body of evidence indicates a correlation between residential/domestic exposure to ELF EMF and childhood leukemia. Breast cancer has been related to ELF EMF exposure more in residential/domestic epidemiological studies than in occupational, but the melatonin hypothesis, although recently revisited, finds little consensus. When studied at the cellular and in vitro level, MFs exert their effect on both human and animal (rat and mice, mainly) cells when used at a high intensity and for a long time. The common response is the production of ROS, which trigger a cascade of other cellular responses which might be the direct consequence of MF exposure. The use of MF is instrumental for the diagnosis and therapy (theranostic) of cancer. MRI is instrumental for the precise diagnosis of different cancers, whereas MNPs open the new era of nanomedicine, allowing (i) the smart delivery of anticancer drugs, (ii) nanosurgery through their magnetomechanic properties, and (iii) fighting the cancer cells in situ by exploiting their capability to generate heat (hyperthermia) via hysteresis loss or through Neel- and Brownian relaxation losses.

Although humans do not perceive the presence or changes of MFs, variations in MF intensity and inclination exert biological effects, with the greatest effects observed at the cellular and subcellular level. The basic response to MF relies on ROS-production with RPM playing a potential role in magneto-perception. Scientists do not generally agree that there is a cause-effect relationship between exposure to MF and cancer, also because of the difficulty in obtaining reproducible effects that are consistent with the hypothesis that MF may cause or promote cancer. MFs might not be the direct cause of cancer but may contribute to ROS-production and generate oxidative stress through RPM 611, which could trigger or enhance the expression of oncogenes 612. Large-scale epidemiological studies are needed to help resolve these issues along with in depth studies on the relationship between magnetoreception, ROS-generation, and cancer.

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