Melanoma: the main culprit is not moles or ultraviolet light, but genes

Moles and melanoma – what is the connection?
MMA based on the materials of the University of Leeds

A new study has proved that people with an increased number of moles are at risk for developing the most dangerous form of skin cancer.

Strictly speaking, melanoma is not a skin cancer. It arises from melanocytes – pigmented cells located in the dermis, but originating from the neural crest. Thus, melanocytes are cells of neural genesis, and when they become malignant, metastases usually spread to the patient's nervous tissue, which makes melanoma such an aggressive and dangerous cancer.

In a study led by Professors Julia Newton Bishop and Tim Bishop of the Melanoma Genetics Consortium (GenoMEL) at the University of Leeds, scientists examined more than 10,000 people, about half of whom were diagnosed with melanoma. In several clinical laboratories in Europe and Australia, 300,000 genomes of patients were also studied to identify which genes may be associated with the development of melanoma. The results of this work can be read in the latest issue of the journal Nature Genetics.

With such a huge and representative sample, it was found that a well-defined genotype is indeed characteristic of melanoma patients. It has long been known that people with red hair and fair skin who quickly burn in the sun are at increased risk of this disease, and patients who have been diagnosed with this often have genes in their DNA responsible for the appearance of freckles. But such genes are also present in perfectly healthy people.

Professors from Leeds were looking for something similar, but, to their surprise, the connection of melanoma with moles and freckles turned out to be much stronger than previously thought. The genes associated with the appearance of moles and a high risk of melanoma are located on chromosomes 9 and 22. They have nothing to do with skin color, but are rigidly associated with the appearance of moles.

In the world, 48,000 people die from melanoma every year. It is most common in men with fair skin. The number of cases of the disease is growing from year to year – it is believed that this is due to social activity, namely, the fact that most people find it useful to spend as much time in the sun as possible. Moreover, prolonged but constant exposure to sunlight on the skin is not as dangerous as periodic ultraviolet radiation in large doses – for example, when a person spends five days a week in the office, then spends the whole weekend under the scorching sun.

Nevertheless, the question of exactly how genetic prerequisites and sunlight are connected with the development of the disease is not very clear yet. Researchers believe that the main problem is still a genetic predisposition, and not ultraviolet radiation, which only provokes the malignancy of melanocytes of the skin.

The study found that at least five genes are associated with melanoma. A person who has all five variants of these genes characteristic of melanoma in his genome is at about 8 times higher risk of the disease than someone who does not have them at all, although the vast majority of people have at least one "dangerous" variant of one of the described genes in their genome.

Currently, research in this area is continuing, and so far the only thing that researchers can advise people with a large number of moles is to stay in the sun less, which, in general, is not news.

Original article: Bishop et al. Genome-wide association study identifies three loci associated with melanoma risk. Nature Genetics, 2009; DOI: 10.1038/ng.411

Portal "Eternal youth" http://vechnayamolodost.ru 23.07.2009