Skin cancers, specifically melanoma, rank among the top 10 most common types of cancers in America and are responsible for about 7,200 deaths a year. There are many risk factors associated with a higher chance of developing melanoma, including exposure to UV rays, age, family history, and having fair skin. Two additional risk factors are the presence of nevi, or moles, on the skin as well as a person’s sex, with males more likely to develop metastatic melanomas than females. Why were these two factors singled out? As a new research study suggests, there may be a genetic link between the sex of an individual and mole formation that would influence melanoma outcomes in patients.
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The study, conducted by Alessia Visconti and colleagues at King’s College in London as well as the University of Turin in Italy, looked at where and how many nevi form on different parts of the body and how sex differences in the human genome influence those locations. They did so by studying pairs of identical twins, as well as comparing a portion of the twins to unrelated people. They counted the number of nevi in four different areas of the body: the head and neck, the trunk (back abdomen and chest), the upper limbs, and the lower limbs. They found that women had twice as many nevi on their lower limbs as men did, while men had more nevi on their torsos. Looking at the factor of heritability, or how much of the variation in a trait is because of genetics as opposed to environmental factors, the scientists found that heritability of nevi count was high for both women and men. They also performed genotypes on each study participant, which allowed them to learn about variations in their DNA sequences. When they compared the differences between all the participants to see if there were any common patterns in variation, they found that there were in fact mutations in genes that correlated with the number of nevi in each of the four locations above.
The results of this study demonstrate that the number of moles, one of the established risk factors for melanoma, is not solely due to the amount or degree of sun exposure, but also to variations in genes present in the body. Furthermore, it demonstrates that men tend to have more moles on the upper limbs and trunk compared to women, which may explain why men have poorer outcomes with melanoma. Men have a higher risk of developing melanoma on the upper body where more of their moles are, and in later stages, cancer can spread to vital organs faster than melanoma that begins in the lower body. Thus, this study raises awareness for the genetic factors that influence melanoma and may inform new diagnosis and treatment options in the different sexes.
Featured Image Source: Damian Gretka
