How UV Radiation Causes Basal Cell Carcinoma and other types of skin cancer
Ultraviolet radiation (UV) refers to a short wavelength electromagnetic band spectrum that is invisible to the human eye. Sources of UV radiation found in everyday life include the sun, tanning beds, and black lights. While we may not be able to see it, certain types of UV radiation may pose a serious health risk.
Skin cancers are abnormal growths that start in the cells that comprise the epidermal layers of the skin. They are the most commonly diagnosed type of cancer in the United States each year representing more cases than all other cancers combined.
Basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma are common skin cancer subtypes affecting different cells of the skin. BCC is the most common type, affecting the inner layer of the epidermis where new skin cells are made. SCC affects the middle and outer layer of the epidermis. Malignant melanoma originates in the pigment-producing cells of the inner layer of the epidermis.
Deoxyribonucleic acid (DNA) functions as a chemical storage medium for genetic information. DNA is contained within packages called chromosomes (highly compacted strands of DNA ) that exist within the nuclei of every living cell in the human body and determines everything about you from the color of your hair to how tall you are to how long you will live.
The structure of DNA is composed of a phosphate group bound to a sugar (ribose) which forms the helix “backbone” of the molecule. The phosphate-sugar backbone is bound to a base - either cytosine, guanine, adenine or thymine - forming a nucleotide. Complementary nucleotides bond to one another to form a tight double-helix coil.
Frequent and ample exposure to harmful UV radiation has been shown to cause significant increases in risk to the development of skin cancer in humans via direct damage to DNA.
Although most of the UV spectrum is absorbed efficiently by atmospheric gasses rendering the radiation ineffective, ultraviolet A (UVA) and ultraviolet B radiation (UVB) pass through and are readily absorbed by cellular life on earth.
The pigment melanin provides our skin with some protection against the sun, but some UV radiation is inevitably absorbed. Most of the radiation absorbed is transformed into heat, but the small amount that isn’t may change the chemical structure of the DNA molecules in unpredictable ways resulting in lesions at sites along the DNA strand.
DNA lesions are classified based on their features:
- Abascal lesions occur where the phosphate-sugar backbone is intact but the base is missing. The easiest way to think of this is to imagine ordering something and receiving an empty box.
- Mismatch lesions form when two non-complementary bases bond. Think of it like trying to put a large object in a box that is too small or putting on two left shoes.
- Modified bases occur when bases undergo changes to their chemical structure. In other words, the information stored on the DNA is corrupt.
- Single-stranded breaks refer to compromises in the phosphate-sugar backbone. In this case, it’s somewhat like receiving a package in a damaged box.
- Double-strand breaks are the most deleterious DNA lesions. The DNA is essentially cracked wide open, like the bottom of a box giving way and the contents (in this case genetic material) spilling out.
In skin cancer, mismatch lesions presenting as covalent bonds among two thymine nucleobases are the direct result of overexposure to UVB. The damage caused may eventually lead to mutations that interrupt normal DNA repair processes, causing abnormal growth. In more than 50% of BCC cases, there is evidence of a mutation in tumor suppressor gene p53, rendering it inactive.
Protecting yourself from the sun is the first step in reducing your risk of developing skin cancer. Limit your time outside during the summer months and apply sunscreen daily.
If you can’t avoid the sun, wear clothing designed to absorb UV radiation. Shield your neck and head from the sun by wearing hats, scarfs, or similar garments. Skip indoor tanning - it’s not any safer than being out in the sun. Sunglasses with UV-absorbing lenses can help keep your eyes safe.
Early detection of skin cancer is crucial in reducing the risk of mortality. Consult the experts at Advanced Cancer Treatment Centers if you have any concerns about your personal risk factors for skin cancer.