Age explains the genetic mutations of skin cancer

Spanish and UK researchers have studied the effect of age on the acquisition and selection of cancer-driving mutations in normal sun-exposed skin — and concluded that age is the factor that explains most of the genetic mutations associated with the appearance and development of different cancerous tumours that affect the skin. Their study has been published in the journal Annals of Oncology.

According to team leader Professor Conrado Martínez-Cadenas, from Jaume I University, the research started by sequencing 46 genes in biopsies of normal skin from 123 healthy individuals, to compare all the mutations that appear and find out the causes, observing both age and phototype or sun exposure, among many other factors. The samples were collected in 2019 and analysed in 2020.

Prof Martínez-Cadenas said that, according to the results, age explains 55.16% of the mutations, while the skin phototype — if it is lighter or darker, with up to six degrees identified — is behind 17.92% of mutations. According to the study’s conclusions, ageing is not only associated with an exponential increase in the number of accumulated somatic genetic mutations in the normal epidermis, but also with the selection and expansion of cancer-associated mutations.

Prof Martínez-Cadenas highlighted that in other types of cancerous diseases, age was already identified as an important factor. “But we initially thought that in the skin, due to being exposed to the sun, the phototype and the history of chronic exposure to the sun would have more weight in mutations, and it is not true.” Indeed, the difference between mutations in areas chronically exposed to the sun and those that are only exposed intermittently is not even significant.

The trend for the appearance of mutations apparently worsens after 60 years, with Prof Martínez-Cadenas saying that “from a certain age, regardless of what you have done, the mutations related to the predisposition to having cancer increase”. The explanation for this fact is that “the human DNA repair systems start working much worse than in youth and early middle age”, he added. On the other hand, smokers also present more mutations of this type in different tissues, “even if these mutations have nothing to do with their lungs”.

Prof Martínez-Cadenas added that the specific causes of somatic mutations that lead to other types of cancer remain unknown in approximately 70% of cases.

Image credit: ©stock.adobe.com/au/goodluz

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