Navigation Links
Exposure to dim light at night may make breast cancers resistant to tamoxifen
Date:7/24/2014

PHILADELPHIA For rats bearing human breast tumors, exposure to dim light at night made the tumors resistant to the breast cancer drug tamoxifen, according to data published in Cancer Research, a journal of the American Association for Cancer Research. The negative effects of dim light exposure on tamoxifen treatment were overcome by giving rats a melatonin supplement during the night.

"Resistance to tamoxifen is a growing problem among patients with hormone receptor-positive breast cancer," said Steven M. Hill, PhD, professor of structural and cellular biology and the Edmond and Lily Safra chair for breast cancer research at Tulane University School of Medicine in New Orleans. "Our data, although they were generated in rats, have potential implications for the large number of patients with breast cancer who are being treated with tamoxifen, because they suggest that nighttime exposure to light, even dim light, could cause their tumors to become resistant to the drug by suppressing melatonin production.

"Our study does not identify how much light exposure is needed to suppress nighttime melatonin production, and potentially drive tamoxifen resistance in humans, but we think that it could be as a little as the amount of light that comes in the bedroom window from a street light," continued Hill, who is also director of the Tulane Center for Circadian Biology. "We are working toward conducting the studies that will answer this question.

"Although melatonin supplements are readily available over the counter at most drug and health-food stores, our research is not at a point where we can make a general recommendation that breast cancer patients taking tamoxifen should go out and buy melatonin," Hill added. "Melatonin is produced by our bodies at a very specific time of day, exclusively during darkness at night, and taking melatonin supplements at the wrong time of day would potentially disrupt the circadian system, particularly the natural melatonin cycle, which may, in itself, paradoxically impair breast cancer responsiveness to tamoxifen."

For the study, Hill and colleagues analyzed rats living in either normal light/dark conditions, with 12 hours of light followed by 12 hours of complete darkness, or conditions in which there were 12 hours of normal light followed by 12 hours of dim light. Melatonin levels in the blood of rats living in normal light/dark conditions rose during the dark period before decreasing again during the light period. In rats living in the dim night light conditions, melatonin levels remained low throughout the light/dark cycle.

Tumor growth in rats living in the dim night light conditions was 2.6-fold faster compared with tumor growth in rats living in normal light/dark conditions. In addition, tumors in rats living in dim night light conditions were completely resistant to tamoxifen, whereas tumors in rats living in normal light/dark conditions regressed significantly. If rats living in dim night light conditions were given a nighttime melatonin supplement, their tumors regressed.

"These data suggest that, in the not-too distant-future, it may be possible to combine melatonin and tamoxifen," said Hill. "However, before this is done we would need to identify the optimal times of day to give the two because if the timing between the two is off, the advantage of giving them in combination may be lost. This brings up another important point: Our levels of melatonin are not determined by sleep, as many people think. It is actually the darkness that is important. During the night, if you sleep in a brightly lit room, your melatonin levels may be inhibited; however, if you are in the dark but cannot sleep, your melatonin levels will rise normally."


'/>"/>

Contact: Jeremy Moore
jeremy.moore@aacr.org
215-446-7109
American Association for Cancer Research
Source:Eurekalert

Related medicine news :

1. Antibody therapy prevents gastrointestinal damage following radiation exposure in mice
2. Genetic variants, tobacco exposure and lung cancer risk
3. Leaded Gas Exposure Linked to Later Violence: Study
4. Majority of states fail to address youth exposure to alcohol marketing
5. Prenatal exposure to pollution especially dangerous for children with asthma
6. Novel biomarkers reveal evidence of radiation exposure
7. Education May Protect Brain From Exposure to Solvents
8. Taking Anti-HIV Meds Prior to Exposure May Help Prevent Infection
9. New research showing how real-life exposure to violence disrupts a childs sleep habits
10. BPA exposure effects may last for generations
11. How MyTownInsurance.com Helps Insurance Carriers Manage their Loss Exposure through On-Line Marketing
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/21/2017)... ... January 21, 2017 , ... Phytocéane invites you to ... the rest of the world with ZANZIBAR SHOWER GEL. Inspired by the beauty of ... Virgin Coconut Oil and moisturizing vegetal coral to create this gentle, crystal-clear shower gel ...
(Date:1/21/2017)... ... January 21, 2017 , ... The Nobel Biocare™ dental ... in media for its creos™ line of bone regenerative products. Specifically, the ... which he utilizes creos™ allo.gain™ bone graft for a variety of bone reconstruction ...
(Date:1/20/2017)... Boca Raton, FL (PRWEB) , ... January 20, 2017 , ... ... supplement development, announced it attended the January ECRM trade show to continue the marketing ... technologically advanced vitamin C supplement, known for providing 400 percent better absorption than traditional ...
(Date:1/20/2017)... ... ... Michael and Betsy Brauser celebrated 5 years of Betsy’s participation in a ... has been life-saving as she has been on the trial for more than six ... ovarian cancer in 2009. She underwent standard chemotherapy but a year later went to ...
(Date:1/20/2017)... ... ... biographical account following a man who went on to support his country and serve the ... Lynn Haven, Florida and at the age of 5, his family moved to Pensacola Florida. ... Navy and got married right out of boot camp. , He and his wife ...
Breaking Medicine News(10 mins):
(Date:1/20/2017)... 2017  Ethicon Endo-Surgery, Inc. announced today ... Inc., a privately held medical device company ... used in operating rooms worldwide. The acquisition ... energy devices with Megadyne,s innovative portfolio of ... in Ethicon,s goal to deliver the most ...
(Date:1/20/2017)... -- Wells Specialty Pharmacy announces the acquisitions and merger of ... Winter Park, Florida and Pharm-EZ Medical, LLC, ... been consolidated into the 3796 Howell Branch Road Facility. ... Chad Tomlinson , former Vice President of Operations, has ... Tomlinson is a Graduate of Florida State University and has ...
(Date:1/19/2017)... The global immunomodulators market is expected ... to a new study by Grand View Research, ... driven by high R&D investments employed by the ... new and therapeutically advanced drugs. This is believed ... unprecedented rate into the immunomodulators market hence providing ...
Breaking Medicine Technology: