Skin Color & Skin Cancer
So far, the process of eumelanin production has been analyzed, as well as the relationship between eumelanin production becoming elevated as a tanning response in the presence of high levels of light radiation being emitted from the sun. The migratory routes of early ancestors have also been compared, along with the mutations within their skin that followed suit. This module intends to answer the questions as to why a lower amount of eumelanin within the skin can lead to skin cancer, as well as how higher levels of eumelanin present is able to defend the skin against harmful radiation.
Considering all the various races and ethnicities in the United States, those who consider themselves to be non-hispanic white have a far greater chance of developing skin cancer throughout the course of their lives. Noticeably, those who have lighter skin tone, such as those who consider themselves to be non-hispanic white, have a lot less eumelanin within their skin cells than other ethnicities. So it’s understood that skin cancer can occur due to harmful light radiation from the sun, and it’s also understood that eumelanin’s rate of production can increase when exposed to sun radiation, but how does the amount of eumelanin within one’s skin affect one’s likelihood to develop skin cancer?
As previously stated in an earlier section, ultraviolet radiation from the sun can penetrate into the skin, down into the cells and into the nucleus. Once the radiation is within the nucleus, it can mutate the DNA’s structure. One of the gene’s that it has the potential to alter is known as the TP53 gene. TP53 is a tumor suppressor gene, meaning that it codes for a tumor suppressor protein, in this case, P53. P53 is an enzyme that is responsible for repairing damaged DNA, initiating apoptosis, or stimulating other reactions that are aimed to suppress a cell’s chances of turning cancerous.
However, if the TP53 gene itself is mutated, not only could its protein be rendered ineffective to protect the cells from cancer formation, but other tumor suppressor genes could be rendered ineffective by the mutation as well. If the intracellular defense mechanisms are made useless by the sun’s radiation, then cancer cells and ultimately a tumor could form without much or any resistance.
But as seen when comparing the rates of skin cancer to the amount of eumelanin produced, there seems to be evidence that eumelanin can play a role in limiting skin cancer’s ability to form as well.
Option 1: Protective Film on the Nucleus
Firstly, eumelanin itself can protect the nucleus from harmful radiation. It forms a protective layer, or film over the outside of the nucleus, and when radiation comes into contact with this film it either absorbs it or bounces off of it.
Option 2: Protective Layer on the Epidermis
Secondly, eumelanin present on the surface of the most superficial layer of the skin, the epidermis, is able to protect the deeper layers of the skin, the dermis and hypodermis. The presence of this layer is also able to protect skin cells that lay more deep within the epidermis as well. Similarly to how eumelanin presence can redirect or absorb radiation to protect the nucleus, it also does the same thing for the epidermis. Skin cells are able to protect themselves without the help of (or very little) eumelanin for about 75% of the time, but the presence of skin cells that have elevated amounts of eumelanin in turn have their rates of protection elevated to around 90% to 95% of radiation being filtered out.
Option 3: Capability to bind with ROS’s
And lastly, eumelanin can also bind to harmful reactive oxygen species (ROS). For the little amount of radiation that can seep through the cracks of the skin’s defenses, and that aren’t able to reach the nucleus due to eumelanin’s protective film, are still able to cause problems at the cellular level. This radiation is able to stimulate the formation of ROS’s, some of which are O2–, H2O2, or a lone OH group. These ROS’s are incredibly reactive, and can cause significant disruptions amongst the DNA’s sugar-phosphate backbone, or the nucleotides themselves. However, eumelanin’s presence within the cell has shown to be potentially able to bind to these ROS’s, further rendering them unable to wreak havoc upon the otherwise defenseless DNA.
Ultimately, eumelanin plays a key role in protecting the skin from harmful radiation due to sunlight exposure. And although the amount of eumelanin within oneself varies from person to person, that doesn’t mean that there aren’t alternative protections that can be used. Sunscreen can be found in a wide range of concentrations, or sun protection factors (SPF). It is important to get exercise and fresh air outside, while experiencing the warmth and vitamin-inducing effects of the sunshine. However, it is essential to properly protect oneself from the harmful effects that the sun can have on ones’s skin. So when at the beach, on the field or at the park during the hot, summer months, be sure to take that extra time to protect from the radiation of the sun.