Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Melanoma risk only partially associated vith exposure to UVB from sunlight

21.12.2005


Researchers at The University of Texas M. D. Anderson Cancer Center have found that the risk of developing melanoma, the most deadly form of skin cancer, is only partially associated with exposure to ultraviolet B (UVB) radiation, the rays in sunlight that increase in summer and cause sunburn.

The report in the Dec. 21 issue of the Journal of the National Cancer Institute also indicates that only nonmalignant skin cancers (basal and squamous cell carcinoma) are strongly associated with exposure to UVB radiation.

That does not mean, however, that sunbathing poses a minimal risk of developing melanoma. Researchers say that ultraviolet A (UVA) radiation, the rays in sunlight that reach the deeper layers of skin and are associated with signs of aging, can damage the DNA in melanocytes, the pigment-producing cells that give rise to melanoma.



"Although we have refined the common wisdom that excess sun exposure is always associated with increased risk of skin cancer, the take-home message for the public is still the same - limit sun exposure and use a sunscreen that blocks both UVA and UVB rays," says the study’s lead investigator, Qingyi Wei, M.D., Ph.D., professor in the Department of Epidemiology.

The study is a painstaking analysis of the ability of UVB radiation to damage a cell’s chromosomes. Chromosomal injury is one way cells can become cancerous; damage to the genes that make up the chromosome is another, and Wei already has shown in previous studies that melanoma patients often have a reduced capacity to repair the DNA damage that results from UVB exposure.

In the novel study, researchers looked at how often chromosomes break in cells from skin cancer patients compared with cells from a control group.

Wei and his team of 16 collaborators at M. D. Anderson gathered white blood cells from 469 skin cancer patients treated at M. D. Anderson (238 of whom were diagnosed with melanoma) as well as from 329 cancer-free control subjects.

Using the theory that the ability to induce breaks in a cell’s chromosome is, in part, based on a person’s genes, and would therefore hold true for all types of body cells, the investigators exposed the blood cells to excess UVB exposure. These findings were linked to whether each of the study participants had one of the three forms of skin cancer. They found that UVB radiation affects cell chromosomes more severely in patients with nonmalignant basal and squamous cell carcinoma than those in melanoma patients. The frequency of UVB-induced chromosome breaks was higher in nonmalignant skin cancer patients than in the control group, but was the same in melanoma patients and the control group. In fact, a higher frequency of chromosomal breaks was associated with a more than twofold-increased risk for both basal cell and squamous cell carcinoma, Wei says.

These findings indicate that in skin cells it is better to have broken chromosomes that cause cells to die or acquire a "simple," treatable cancer, than for the skin cells to remain intact but sustain genetic damage that can lead to much more serious cancer, Wei adds.

They also found a strong dose-response relationship among UVB radiation, chromosome breaks and squamous cell carcinoma. Sun exposure increases a person’s risk of developing squamous cell carcinoma. Investigators discovered, however, that the risk of developing basal cell carcinoma increases to a certain point, given exposure to UVB radiation, but does not continue to increase with excess sun exposure. These experimental data fit well to the incidence data of skin cancers in the general population.

Wei says these conclusions may help explain for why nonmalignant skin cancers are so common - more than 1 million cases are diagnosed each year in the United States - and why they are so easy to treat. Squamous skin cells lie near the top of the skin’s layers, while basal skin cells lie near the base of the skin’s layers. In both cases, these cells actively reproduce. When their chromosomes are damaged by sunlight, the cells often die or form a simple kind of cancer at the surface that is nonmalignant and easy to remove by surgery or treat in other ways, he says.

Melanoma, on the other hand, is now known to be resistant to chromosomal breaks from UVB radiation, which means that the cell’s chromosomes stay intact long enough to continually amass genetic damage from UVA radiation, according to previously published data. "This allows the cells to hang in there longer, potentially passing on genetic mutations to daughter cells which can result in a cancer that is not sensitive to treatment," Wei says. "If you think of a chromosome as walls that hold up the house, which is the cell, and DNA as individual bricks, then in common squamous and basal cell carcinoma, UV in sunlight knocks down the walls, and usually these cells die or form a nonmalignant cancer," says Wei.

"But if UV sunlight doesn’t hurt the walls too much, but endangers the house with broken bricks, this can form a much more malignant cancer in which the cell can continue to replicate, passing on to daughter cells genetic mutations that can lead to a dangerous cancer," he says.

According to the National Cancer Institute, close to 60,000 cases of melanoma are expected in 2005, along with more than 7,700 associated deaths.

Stephanie Dedeaux | EurekAlert!
Further information:
http://www.mdanderson.org

More articles from Life Sciences:

nachricht Light-driven reaction converts carbon dioxide into fuel
23.02.2017 | Duke University

nachricht Oil and gas wastewater spills alter microbes in West Virginia waters
23.02.2017 | Rutgers University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Organ-on-a-chip mimics heart's biomechanical properties

23.02.2017 | Health and Medicine

Light-driven reaction converts carbon dioxide into fuel

23.02.2017 | Life Sciences

Oil and gas wastewater spills alter microbes in West Virginia waters

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>