A recent article published in Frontiers in Medicine described skin cancer as an environmental cancer—UV radiation being the major causative agent. Sunscreens have long been part of the strategy for protection against skin cancer.

Sun Protection Factor (SPF) is a measurement that is used in the ratings of sunscreens. Scientifically, SPF is defined as the ratio of the least amount of ultraviolet energy required to produce a minimal erythema on skin protected by sunscreen to the amount of energy required to produce the same erythema on unprotected skin i.e., the minimal erythema dose.

It has been known that UV-radiation damage is directly, is absorbed by DNA and leads to the formation of pyrimidine dimers. This DNA damage is repaired by groups of enzymes that “excise” these dimers and replace them with the correct sequences. However, when this repair mechanism fails, permanent mutations can occur. The effectiveness of sunscreens is tested by the ability to prevent erythema of skin—around 300 nm is the typical action spectrum that induces both erythema and the formation of pyrimidine dimers.

It is now established that UV-induced skin damage is responsible for cutaneous melanoma. Additionally, a high frequency of BRAF gene-mutations occur in cutaneous melanomas as compared with uveal or mucosal melanomas, suggesting a link between BRAF mutations and UV exposure. Whole-exome and whole-genome sequencing of melanomas have shown many UV signatures in melanomas from sun-exposed body sites suggesting that some BRAF mutations can be caused by “non-informative UV-induced mutations” i.e., changes that do not occur at a dipyrimidine sites. Sunscreens block UV radiation from entering the skin, and hence, prevents cutaneous melanoma.

Mutations of the p53 gene are different in sun-damaged skin and other organs while other tumors have different mutations. Scientists state that sunscreens do reduce these p53 mutations and therefore, sunscreens in general can be expected to reduce the risk of skin cancer.

Source: Frontiers in Medicine (Lausanne). 2019;6:195. Published 2019 Sep 4. doi:10.3389/fmed.2019.00195.