Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger, an indirect antioxidant, as well as an important immunomodulatory agent. In both in vitro and in vivo investigations, melatonin protected healthy cells from radiation-induced and chemotherapeutic drug-induced toxicity. Furthermore, several clinical studies have demonstrated the potential of melatonin, either alone or in combination with traditional therapy, to yield a favorable efficacy to toxicity ratio in the treatment of human cancers. This study reviews the literature from laboratory investigations that document the antioxidant and oncostatic actions of melatonin and summarizes the evidence regarding the potential use of melatonin in cancer treatment. This study also provides rationale for the design of larger translational research-based clinical trials.

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There have been allegations in the media and in the courts that cell phones and other types of hand-held transceivers are a cause of cancer. There have also been numerous public objections to the siting of TV, radio and cell phone transmission facilities because of a fear of cancer induction. A recent publication in Radiation Research by Repacholi et al. (147, 631-640, 1997) which suggests that exposure to radiofrequency (RF) radiation may increase lymphoma incidence in mice has contributed to this controversy. The goal of this review is to provide biomedical researchers a brief overview of the existing RF radiation-cancer studies. This article begins with a brief review of the physics and technology of cell phones. It then reviews the existing epidemiological studies of RF radiation, identifying gaps in our knowledge. Finally, the review discusses the cytogenetics literature on RF radiation and the whole-animal RF-radiation carcinogenesis studies. The epidemiological evidence for an association between RF radiation and cancer is found to be weak and inconsistent, the laboratory studies generally do not suggest that cell phone RF radiation has genotoxic or epigenetic activity, and a cell phone RF radiation-cancer connection is found to be physically implausible. Overall, the existing evidence for a causal relationship between RF radiation from cell phones and cancer is found to be weak to nonexistent.

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The objective of this study was to examine the potential radioprotective properties of pharmacological doses of melatonin in whole-body irradiated mice. CD2-F1 male mice were treated with melatonin, a secretory product of the pineal gland, and then whole-body irradiated with an acute dose (150 cGy) of 137Cs gamma rays. Peripheral blood and bone marrow cells were examined for genetic damage, which was determined by comparing the incidence of micronuclei (MN) in both melatonin pre-treated and non-treated irradiated animals (and control mice). The percentages of polychromatic erythrocytes (PCEs) in unirradiated mice ranged between 3.1 +/- 0.23 and 3.2 +/- 0.19 in the peripheral blood and between 51.0 +/- 2.03 and 52.8 +/- 2.00 in the bone marrow. Whole-body irradiation resulted in a significant decrease in the percentages of PCEs in the peripheral blood and bone marrow cells. In both tissues, irradiated mice that were pre-treated with melatonin (5 or 10 mg/kg) exhibited a dose-dependent increase in the observed incidence of PCEs relative to the expected incidence. The incidence of MN in unirradiated mice ranged between 4.2 +/- 0.92 and 4.6 +/- 0.97 in the peripheral blood and between 5.0 +/- 1.05 and 5.5 +/- 1.08 in the bone marrow. Whole-body irradiation resulted in a significant increase in the incidence of MN in both tissues. In both tissues, irradiated mice that were pre-treated with melatonin exhibited a significant and dose-dependent reduction in the observed incidence of MN (relative to the expected incidence). Under the experimental conditions tested, the data indicate that melatonin has the ability to protect the genetic material of hematopoietic cells of mice from the damaging effects of acute whole-body irradiation.

Human peripheral blood lymphocytes which were pretreated in vitro with melatonin, an endogenously synthesized pineal hormone, for 20 min at 37 +/- 1 degree C exhibited a significant and concentration-dependent reduction in the frequency of gamma-radiation-induced micronuclei compared with irradiated cells which did not receive the pretreatment. The extent of the reduction observed with 2.0 mM melatonin was similar to that found in lymphocytes pretreated for 20 min with 1.0 M dimethylsulfoxide, a known free radical scavenger. These observations indicate that melatonin may have an active role in protection of humans against genetic damage due to endogenously produced free radicals, and also may be of use in reducing damage due to exposure to physical and chemical mutagens and carcinogens which generate free radicals.