Sunscreen alone cannot be relied upon to prevent malignant melanoma, the most deadly form of skin cancer, a new study has found.
The study explains more about the mechanism by which UV light leads to melanoma and also explores the extent to which sunscreen is able to prevent UV light from damaging healthy cells.
In the study, carried out at Cancer Research UK's Manchester Institute, based at the University of Manchester, and at The Institute of Cancer Research, London, scientists examined the molecular effects of UV light on the skin of mice at risk of melanoma and whether disease development was blocked by sunscreen.
UV light directly damages the DNA in the skin's pigment cells, increasing the chances of developing melanoma.
The researchers showed that it causes faults in the p53 gene, which normally helps protect from the effects of DNA damage caused by UV light.
The study also showed that sunscreen can greatly reduce the amount of DNA damage caused by UV, delaying the development of melanoma in the mice.
But, importantly, the study also found that sunscreen did not offer complete protection and UV light could still target p53 to induce melanoma, albeit at a reduced rate.
"UV light has long been known to cause melanoma skin cancer, but exactly how this happens has not been clear. These studies allow us to begin to understand how UV light causes melanoma," said Professor Richard Marais, study author and Cancer Research UK scientist, based at the University of Manchester.
"UV light targets the very genes protecting us from its own damaging effects, showing how dangerous this cancer-causing agent is.
"Very importantly, this study provides proof that sunscreen does not offer complete protection from the damaging effects of UV light.
"This work highlights the importance of combining sunscreen with other strategies to protect our skin, including wearing hats and loose fitting clothing, and seeking shade when the sun is at its strongest," Marais said.
The research was published in the journal Nature.