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Melatonin-Depleted Blood from Premenopausal Women Exposed to Light at Night Stimulates Growth of Human Breast Cancer Xenografts in Nude Rats
Blood with low melatonin from premenopausal women exposed to light at night promotes growth of human breast tumors in rats
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Abstract
Exposure to bright, white light at night can suppress melatonin levels and increase tumor growth in breast cancer models.
- Increasing intensities of white fluorescent light during dark phases resulted in a dose-dependent reduction of nocturnal melatonin levels in rats.
- Tumor growth and linoleic acid uptake were stimulated in rat hepatomas and human breast cancer xenografts exposed to higher light intensities.
- Blood samples collected from healthy, premenopausal women showed that melatonin-rich blood collected at night reduced tumor proliferation when perfused to tumors.
- Tumors perfused with blood from subjects exposed to bright light at night exhibited a pattern of high proliferative activity similar to daytime conditions.
- These findings suggest that the circadian melatonin signal may play a role in inhibiting breast cancer growth and its effects can be disrupted by light exposure at night.
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