Being the daughter of a private-practicing dermatologist for nearly twenty years, the topic of the sun and the dangers that come along with it have always been on my mind. Whether it be text messages kindly reminding me to both apply and reapply sunscreen, warnings not to tan, or even forcing me to wear hats on the beach, sun safety has always been a priority in the Glass family household. Of course, I was always fully aware that sitting out in the sun for countless hours could not possibly be healthy for me, but I never thought to what extent this seemingly harmless activity was damaging my body. Isn’t a sunburn just a sunburn? Can tanning really be that bad for you? Only once I embarked on my research journey of the genotoxic effects of sun exposure did I realize how naïve I had been regarding its consequences.
The preliminary step to understanding the damage that the sun can cause is first understanding what sunlight is. Sunlight is made up of radiation, the majority of which is visible and ultra-violet. UVR, ultraviolet radiation, is categorized into three distinct types, each with different wavelengths: UVA (315-400 nm), UVB (280-315nm), and UVC (100-280nm). UVB rays are responsible for sunburns as they penetrate the epidermis, the top layer of the skin. Although UVA rays penetrate to deeper layers of the skin, they are still harmful and can cause just as much damage. UVC on the other hand, is almost completely absorbed by the Earth’s atmosphere and therefore less frequently damages the skin.
Skin cancer results from uncontrolled growth of cells found in different layers of the skin and is one of the most commonly diagnosed cancers in the United States. The seriousness of this disease is highlighted by the fact that the number of Americans who have had skin cancer over the past three decades is higher than the number for all other cancers combined. Nonmelanoma skin cancer, including basal cell carcinomas and squamous cell carcinomas, is a major public health concern.
The mechanism by which UV radiation can induce non-melanoma skin cancer is through DNA damage. When our skin cells are exposed to UV radiation, various oncogenes are activated while the tumor suppressor genes are simultaneously inactivated. This results in the improper survival and growth of skin cells. UV radiation also plays an important role in a person’s immune system. People who are immunosuppressed, like organ transplant recipients, are more likely to get skin cancer. Although immunosuppression is needed to prevent a rejection of a transplant, there is an assumed risk of developing skin cancer. For instance, over 50% of renal transplant recipients on long-term immunosuppressive therapy have developed at least one non-melanoma skin cancer. A groundbreaking experiment done by Kripke and colleagues sheds light on the connection between immunosuppression and UV radiation. Two groups of mice were injected with tumor cells, however, only one group was subsequently exposed to UV radiation. In the mice that were exposed to radiation, suppressor cells were produced inhibiting
the mice’s ability to fight off growth of the tumor. In the mice that were not exposed to the radiation, no tumor growth was observed.
Sunscreens, a popular prevention method, work by blocking UV radiation from entering the skin. However, after investigating the type of DNA damage that can be caused by sun exposure, I was interested in learning about the emerging compounds that work to reverse the biochemical changes causing skin cancers on a cellular level. Recently, pharmacologic interventions as well as dietary manipulations are being investigated as potential prevention methods. Since ancient times, the consumption of phytochemicals (chemical compounds derived from plants) has proven to have health benefits, including protection of the skin from sunlight. Lycopene and pomegranates for instance, possess both antioxidant and anticancer properties. Green tea also has been shown in studies to prevent skin cancer by enhancing DNA repair.
Although the damages and dangers of exposure to the sun seem daunting and overwhelming, it is comforting to know that there are new means of prevention and treatment that are being studied at great lengths. Perhaps in the near future, simply adding “photo-protective” foods to our daily diets will make sunscreen use a thing of the past.