A genetic variant that greatly boosts the risk of testicular cancer may protect light-skinned individuals from skin cancer by helping them to tan.

A team led by Douglas Bell at the US National Institutes of Health in Bethesda, Maryland, and Gareth Bond at the University of Oxford, UK, surveyed data from genome-wide association studies (GWAS). They focused on polymorphisms in DNA binding sites for the tumour-suppressor protein p53. One variant, in a gene called KITLG, has one of the strongest effects of any pro-cancer variant identified by GWAS and was vastly more common in caucasians. In mice, the p53–KITLG interaction boosted the growth of pigment-producing cells after exposure to ultraviolet radiation, and so might protect against excessive sun damage and cancer.

Cell 155, 410–422 (2013)