Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Artificial light at night stimulates breast cancer growth in laboratory mice

21.12.2005


Results from a new study in laboratory mice show that nighttime exposure to artificial light stimulated the growth of human breast tumors by suppressing the levels of a key hormone called melatonin. The study also showed that extended periods of nighttime darkness greatly slowed the growth of these tumors.



The study results might explain why female night shift workers have a higher rate of breast cancer. It also offers a promising new explanation for the epidemic rise in breast cancer incidence in industrialized countries like the United States.

The National Cancer Institute and the National Institute of Environmental Health Sciences, agencies of the federal National Institutes of Health, provided funding to researchers at the Bassett Research Institute of the Mary Imogene Bassett Hospital in Cooperstown, New York and The Thomas Jefferson University in Philadelphia, Pa. The results are published in the December 1, 2005 issue of the scientific journal Cancer Research.


"This is the first experimental evidence that artificial light plays an integral role in the growth of human breast cancer," said NIEHS Director David A. Schwartz, M.D. "This finding will enable scientists to develop new strategies for evaluating the effects of light and other environmental factors on cancer growth."

"The risk of developing breast cancer is about five times higher in industrialized nations than it is in underdeveloped countries," said Les Reinlib, Ph.D., a program administrator with the NIEHS’ grants division. "These results suggest that the increasing nighttime use of electric lighting, both at home and in the workplace, may be a significant factor."

Previous research showed that artificial light suppresses the brain’s production of melatonin, a hormone that helps to regulate a person’s sleeping and waking cycles. The new study shows that melatonin also plays a key role in the development of cancerous tumors.

"We know that many tumors are largely dependent on a nutrient called linoleic acid, an essential fatty acid, in order to grow," said David Blask, M.D., Ph.D., a neuroendocrinologist with the Bassett Research Institute and lead author on the study. "Melatonin interferes with the tumor’s ability to use linoleic acid as a growth signal, which causes tumor metabolism and growth activity to shut down."

To test this hypothesis, the researchers injected human breast cancer cells into laboratory mice. Once these cells developed into cancerous tumors, the tumors were implanted into female rats where they could continue to grow and develop.

The researchers then took blood samples from 12 healthy, premenopausal volunteers. The samples were collected under three different conditions – during the daytime, during the nighttime following 2 hours of complete darkness, and during the nighttime following 90 minutes of exposure to bright fluorescent light. These blood samples were then pumped directly through the developing tumors.

"The melatonin-rich blood collected from subjects while in total darkness severely slowed the growth of the tumors. "These results are due to a direct effect of the melatonin on the cancer cells," said Blask. "The melatonin is clearly suppressing tumor development and growth."

In contrast, tests with the melatonin-depleted blood from light-exposed subjects stimulated tumor growth. "We observed rapid growth comparable to that seen with administration of daytime blood samples, when tumor activity is particularly high," Blask said.

According to the researchers, melatonin exerts a strong influence on the body’s circadian rhythm, an internal biological clock that regulates sleep-wake cycle, body temperature, endocrine functions, and a number of disease processes including heart attack, stroke and asthma. "Evidence is emerging that disruption of one’s circadian clock is associated with cancer in humans, and that interference with internal timekeeping can tip the balance in favor of tumor development," said Blask.

"The effects we are seeing are of greatest concern to people who routinely stay in a lighted environment during times when they would prefer to be sleeping," said Mark Rollag, Ph.D., a visiting research scientist at the University of Virginia and one of the study co-authors. "This is because melatonin concentrations are not elevated during a person’s normal waking hours."

"If the link between light exposure and cancer risk can be confirmed, it could have an immediate impact on the production and use of artificial lighting in this country," said Blask. "This might include lighting with a wavelength and intensity that does not disrupt melatonin levels and internal timekeeping."

"Day workers who spend their time indoors would benefit from lighting that better mimics sunlight," added Blask. "Companies that employ shift workers could introduce lighting that allows the workers to see without disrupting their circadian and melatonin rhythms."

John Peterson | EurekAlert!
Further information:
http://www.niehs.nih.gov/

More articles from Health and Medicine:

nachricht Researchers release the brakes on the immune system
18.10.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht Norovirus evades immune system by hiding out in rare gut cells
12.10.2017 | University of Pennsylvania School of Medicine

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>