Use of SPF30 sunscreen before exposure to ultraviolet-B delays melanoma, says study

Use of sun protection factor 30 (SPF30) sunscreen prior to exposure to ultraviolet-B (UVB) light can delay incidence of melanoma, according to a new research conducted by Ohio State University Comprehensive Cancer Center.

The Pelotonia-funded study was performed on a mouse model of the disease.

It was carried out by Ohio State University Comprehensive Cancer Center, Department of Molecular Genetics assistant professor Christin Burd and a senior undergraduate biology student Andrea Holderbaum.

The study found that if the genetically engineered mice were exposed to a single dose of UVB light one day after applying chemical 4-hydroxytamoxifen (4OHT) to the skin, melanomas appeared much more rapidly, and there were many more tumours.

Researchers used the mouse model to test the ability of different sunscreens labelled SPF30 to prevent melanoma.

Sunscreens containing a range of UV-blocking agents were applied to the mice prior to exposure to the UVB light and all the sunscreens were found to delay melanoma onset and reduce tumour development.

Genetically engineered mice developed melanoma around 26 weeks after 4OHT was applied to the skin.

However, the study has not compared the melanoma-preventing capacity of the different sunscreens.

Burd said: "Over the past 40 years, the melanoma incidence rate has consistently increased in the United States.

"Sunscreens are known to prevent skin from burning when exposed to UV sunlight, which is a major risk factor for melanoma. However, it has not been possible to test whether sunscreens prevent melanoma, because these are generally manufactured as cosmetics and tested in human volunteers or synthetic skin models.

"We have developed a mouse model that allows us to test the ability of a sunscreen to not only prevent burns but also to prevent melanoma."

Burd also explained that a major limitation of the study is that the short dose of UVB used in these experiments is equivalent to the amount of UVB exposure a person might experience in a weeklong beach vacation.

She added: "Sunscreens were never meant to handle a week’s worth of sun given at one time, and we are working to reduce the UVB dose we use in our studies."

Burd noted that another limitation of the model is that it used only UVB light, which means that the mice were exposed to only a portion of the entire UV spectrum present in sunlight.

She added: "We are currently seeking funding to purchase a solar simulator, which will better model all wavelengths of sunlight.

"However, funding for these studies can be hard to come by because sunscreens are primarily developed by the cosmetics industry, which has pledged not to use animals in the development of their products."

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Image: Christin Burd, assistant professor in Ohio State University Comprehensive Cancer Center Department of Molecular Genetics and the Department of Molecular Virology, Immunology & Medical Genetics. Photo: courtesy of AACR.