Cancer's Link Behind Sun Damage

Melanoma genetic evidence for ultraviolet exposure

/ Author:  / Reviewed by: Chris Galloway, M.D.

(RxWiki News) An important part of the scientific process is trying to figure out why common sense beliefs are true. Observing that sun damage and sun burn seemed to cause melanoma still needed solid proof.

Molecular evidence for the role of sun exposure was revealed.  

More important than which genes were mutated was the pattern of the mutations, which was very consistent with the alterations that are caused by ultraviolet light.

"Talk to your doctor if you notice any suspicious changes in a mole."

Researchers concluded the level of damage and mutations were clearly related to the amount of lifetime exposure to ultraviolet light without protection.

Scientists took 25 different aggressively metastatic melanoma tumors from different patients and sequenced the entire genome, looking at all of the DNA that had been changed from the original cell.

An average of 80,000 DNA mutations were found in each melanoma tumor. This finding strongly supports the central cancer theories that it takes quite a few genetic errors to alter a normal cell into a tumor.

Many times, extensive damage from ultraviolet light will cause a cell to die. In the case of these 25 melanomas, the damage caused specific mutations that caused cancer, instead of the cell dying.

Two genes involved in sending signals important to cell growth,  BRAF and NRAS, were effected in 24 of the 25 tumors. 

One other changed gene leaped out of the data: PREX2, previously implicated in breast cancer for blocking a tumor-suppressor pathway, was altered in 44 percent of patients. Many cancers share these alterations in growth genes, referred to as oncogenes in the scientific literature.

The researchers concluded that PREX2 seems to be important for cancer aggression as mutations in the gene meant greatly increased levels of growth in those cancers.

"By looking across the entire genome you can more accurately determine the background mutation rate and the different classes of mutations, and more confidently describe the pattern of ultraviolet-induced mutagenesis in melanoma," said Michael F. Berger, coauthor of the paper.

The study was published May 9, 2012 in the journal Nature.

No conflicts of interest were reported by the researchers.

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Review Date: 
May 11, 2012
Last Updated:
July 5, 2012