From one to ten
Scientists have found out how many mutations are needed to cause cancer
The appearance of only ten "successful" mutations in the DNA of most cells is enough for them to "rebel" and give rise to a malignant cancer, according to an article published in the journal Cell (Martincorena et al., Universal Patterns of Selection in Cancer and Somatic Tissues).
"We have solved one of the oldest questions concerning cancer – how many mutations must appear in DNA for a normal cell to turn into a cancerous one. As it turned out, their number is extremely small. For example, typical liver cancer cells contain about 4 mutations, and rectal cells generate cancer through about 10 "typos" in DNA," said Peter Campbell from the Sanger Institute (in a press release 1 to 10 mutations are needed to drive cancer, scientists find, figure from which is given below – VM).
Cancer is now considered one of the main causes of human death in developed countries, and its main feature is that the frequency of its development increases markedly in older years. As scientists suggest, this is due to two things – the deterioration of the body's ability to "repair" breaks in DNA at the onset of old age and the accumulation of a number of potentially dangerous, but not fatal mutations in the genome.
Scientists have been trying to use both of these patterns for a long time to predict the likelihood of developing cancer in a particular person, but so far such forecasts either do not work at all, or are extremely low in accuracy.
British geneticists have calculated for the first time how many mutations are required for the origin of most of the most common types of cancer by studying the genomes of approximately 7,600 cancerous tumors extracted from the bodies of patients in British clinics.
The development of cancer, as scientists explain, follows the same Darwinian laws as the evolution of all other forms of life – favorable mutations that contribute to the survival of cancer cells gradually accumulate in the body, and unsuccessful versions of them lead to the death of their carriers and their disappearance from a kind of cancer "gene pool".
By analyzing and comparing the DNA of cancer cells extracted from tumors of the same type, but belonging to different people, Campbell and his colleagues hoped to find such "successful" mutations and understand what minimum number of them is necessary for the development of cancer, and how long they can "survive" in the human body.
This analysis revealed two curious things that biologists did not expect to see. Firstly, it turned out that "successful" mutations can exist in cells for a very long time and not attract the attention of the body's self-defense systems, which contributes to their accumulation and the development of cancer even if mutations appear in a particular body tissue quite rarely.
Secondly, the number of such "typos" in DNA necessary for the development of cancer turned out to be extremely small – in some organs cancer can occur even after one such mutation, and in others – after 3-4 or 10 changes in the structure of a number of key genes.
What is even more interesting, about half of these "successful" mutations were in genes that had not previously been associated with the development of cancer, and were unknown to scientists studying malignant tumors. Studying them, geneticists hope, will help us better assess the likelihood of developing cancer, and also help us understand how the accumulation of mutations may be associated with aging of the body.
Portal "Eternal youth" http://vechnayamolodost.ru