I change melanoma for testicular cancer
Testicular cancer as a payback for UV protection
In their research, Gareth Bond and his colleagues worked with the p53 protein, mutations in which occur in most tumors. p53 monitors the state of DNA and, if a lot of damage accumulates in it, launches a cellular suicide program; if p53 does not work, mutations in DNA can easily make the cell malignant.
Because of this, inherited mutations in the p53 gene are extremely rare: natural selection would simply purge them from the population. But they still exist, and it is not always clear what allowed them to avoid negative selection.
The researchers analyzed about 60 thousand nucleotide substitutions that can be found in the human genome. Such replacements cause variations in the color of hair or eyes, but can also cause a variety of diseases. Comparing healthy cells with cancerous ones, the scientists found 86 nucleotide substitutions that were associated with cancer and were located in DNA regions controlled by p53. As a result, it was possible to determine the nucleotide substitution, to which p53 gravitated especially strongly. And she, as it turned out, was associated with testicular cancer.
Evolutionary analysis has shown that this mutation has become fixed in the genome as people move from Africa to the north: in Caucasians it occurs in 80% of cases, while in blacks – only in 24%. And, probably, this is the reason why white people get testicular cancer 4-5 times more often.
When a malicious mutation is fixed in the genome, it means that there is some benefit from it, and this benefit outweighs the harm. Earlier studies have shown that the gene in which an oncogenic nucleotide replacement was found is needed to protect the skin from solar ultraviolet radiation. New experiments have revealed that the work of the protective gene depends on p53, which activates it, and the stronger p53 acts, the better the protection, the more melanocytes appear in the skin.
The detected mutation enhances the interaction between p53 and the UV protection gene, but it also increases the likelihood that a person will get testicular cancer. It is also worth saying that of all the nucleotide substitutions found, this one turned out to be strong enough to influence the behavior of p53.
Drawing from an article in Cell – VMObviously, in evolution, this type of tumor has become a lesser evil than DNA damage from ultraviolet radiation, which inevitably had to appear in "pale" people who left Africa.
The results of the study are published in the journal Cell (Zeron-Medina et al., A Polymorphic p53 Response Element in KIT Ligand Influences Cancer Risk and Has Underground Natural Selection).
Prepared based on ScienceNOW: Testicular Cancer May Be the Price Paid for Sun Protection.
Portal "Eternal youth" http://vechnayamolodost.ru14.10.2013