Patients suffering from a type of skin cancer known as melanoma who also carry genetic variants in the gene MC1R - associated with red hair and freckles - have 42% more mutations in their cancers compared to individuals without these variations, reports a study published in Nature Communications this week. These findings have implications for understanding individuals’ risk of developing melanoma.

The protein MC1R, or the melanocortin 1 receptor, is involved in skin pigmentation. It is well known that some individuals carry genetic variants of MC1R: two copies of these so-called ‘R variants’ are associated with red hair, while people with one copy of an R variant do not generally have red hair but show altered responses to UV, or sun exposure, compared to people with no R variants. MC1R variants are also known to be associated with an increased risk of developing melanoma.

David Adams and colleagues investigated how many mutations were present in melanoma samples taken from cohorts of patients with and without R variants. They analysed two previously published datasets composed of 273 and 132 melanoma samples each, including sequenced DNA information from the samples. They found that individuals with one or two R variants displayed an increase in the number of mutations in the DNA of their melanoma samples compared to those with no R variants. When they examined only one specific type of mutation (involving a base change from C to T) in the melanomas of patients with one or more R variants, they found an increase of 42% in the number of these mutations in the melanoma samples of these patients.

In addition, the authors found that another factor associated with an increase in the number of mutations was age: each year of age was associated with a 1.7% increase in the number of mutations in the melanoma samples.