23 July 2014
Exposure to light at night can render breast cancer completely resistant to tamoxifen, a widely used breast cancer drug, says a new study by Tulane University School of Medicine cancer researchers.
In a new study entitled 'Circadian and Melatonin Disruption by Exposure to Light at Night Drives Intrinsic Resistance to Tamoxifen Therapy in Breast Cancer,' published in the journal Cancer Research, experts claim that light exposure shuts off production of the hormone melatonin, which is vital to the success of tamoxifen in treating breast cancer.
In tests, melatonin by itself was found to delay the formation of tumors and significantly slow their growth, but tamoxifen caused a dramatic regression of tumors in subjects with either high nighttime levels of melatonin during complete darkness, or those receiving melatonin supplementation during dim light at night exposure.
Principal investigator and co-leader David Blask explained: "High melatonin levels at night put breast cancer cells to 'sleep' by turning off key growth mechanisms. These cells are vulnerable to tamoxifen. But when the lights are on and melatonin is suppressed, breast cancer cells 'wake up' and ignore tamoxifen.
According to the researchers, the study could make light at night a new and serious risk factor for developing resistance to tamoxifen and other anti-cancer drugs, and make the use of melatonin in combination with tamoxifen, administered at the optimal time of day or night, standard treatment for breast cancer patients.
Posted by Philip Briggs
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