Melatonin reduces estrogen available to tumors and inhibits angiogenesis
Melatonin is a hormone that communicates information concerning environmental light conditions to various parts of the body and plays a vital role in the synchronization of circadian rhythms (the body clock). Melatonin has also been shown to have anti-cancer properties, especially in breast cancer. Low levels of melatonin as a result of excessive exposure to light at night is associated with increased risk of breast cancer. Now a new study has demonstrated that melatonin reduces estrogen production in normal breast cells near malignant cells, in addition to reducing tumor angiogenesis (new blood vessel formation).
Anti-cancer activities of melatonin
Melatonin influences the expression of genes involved in cell proliferation, immune responses, cell adhesion, apoptosis (programmed cell death), cell cycle, and angiogenesis in ways that have anticancer effects in breast cancer cells. For example, melatonin induces the expression of tumor suppressor genes. Melatonin has also been shown to interfere with estrogen-signaling pathways and reduce aromatase activity (in which androgens are converted into estrogens) in human breast cancer cells, thereby inhibiting breast cancer growth.
Sources of melatonin
Melatonin is synthesized and secreted by the pineal gland in the brain. Melatonin is produced at night (or in darkness) and nocturnal light disrupts melatonin synthesis. Women can maintain their melatonin levels by getting enough sleep, avoiding night shift work and light exposure at night (using red rather than blue or green light when light is necessary), and consuming melatonin-rich foods.
Common foods that are very good sources of melatonin include almonds, cherries (especially sour or tart cherries), and tomatoes. Other very good sources of melatonin include white and black mustard seeds, sunflower seeds, fennel seed, red, brown and green algae, and flaxseed. Walnuts, oats, and sweet corn also contain some melatonin. On the other hand, red meat consumption has been shown reduce circulating melatonin.
While melatonin supplements, which typically are taken to aid sleep or as part of an anti-aging regimen, are effective in increasing circulating melatonin levels, there are few studies concerning their impact on breast cancer risk or breast cancer recurrence. Safe and effective dosages for breast cancer survivors have not been established and we do not encourage taking melatonin.
Latest research shows that melatonin reduces VEGF
The study referenced at the beginning of this news article was designed to investigate the role of melatonin in the regulation of vascular endothelial growth factor (VEGF) in breast cancer cells. VEGF is vital for tumor blood vessel formation. To conduct the study, the authors co-cultured hormone receptor positive (ER+/PR+) MCF-7 human breast cancer cells with human umbilical vein endothelial cells (HUVECs).
VEGF was found to stimulate the proliferation of HUVECs when VEGF was added to the culture, whereas melatonin counteracted this effect. Furthermore, melatonin was found to inhibit VEGF production and VEGF mRNA expression in MCF-7 cells. The co-culturing of breast cancer cells with umbilical endothelial cells stimulated the proliferation of the endothelial cells and heightened VEGF levels in the culture media. In addition, conditioned media from MCF-7 cells stimulated the proliferation of HUVECs. Melatonin was shown to counteracted all three effects.
Taken together, the findings indicate that melatonin might play a role in the interactions between malignant cells and nearby endothelial cells by down regulating VEGF expression in the cancer cells. The authors conclude that lower levels of VEGF induced by melatonin could be important in reducing the number of estrogen-producing normal cells in local proximity to malignant cells, in addition to reducing tumor angiogenesis.