The second one is not superfluous
The most tenacious cancer cells have a "spare" – another genome
Cancer cells multiply rapidly, mutate rapidly and form clones that are resistant to external influences, which significantly complicates the fight against them. Scientists have approached the development of a cancerous tumor as an evolutionary process to which the principles of Darwinian natural selection are applicable, having developed a new antitumor strategy
One of the main features of cancer cells is that they divide quickly. At the same time, many errors may occur in the process of copying genetic material, and all these structural disorders of the genome are transmitted to the next generations of cells. Therefore, in tumor cells, unlike healthy human cells, it is rare to see the "correct" 46 chromosomes, but chromosomes with duplicated or, conversely, missing sections are often found.
In some cancer cells, there is even a complete doubling of the genome! The reason for this phenomenon is unknown, but such duplication of hereditary information gives a certain advantage to a progressive cancer tumor – it becomes clear if we turn to the principles of natural selection.
As you know, most higher organisms (and all multicellular animals) practice sexual reproduction. In other words, their offspring carry the genes of both parents. And although this is not the most "economical" way of reproduction, organisms go for it, since it is more preferable for the survival of the species. Why? One of the reasons is that during asexual reproduction (or in the case of parthenogenesis in higher organisms), all genetic mutations accumulated by the "parent", including "harmful" ones, are transmitted to the offspring. There is no possibility to return to the original version of the genes, and when a critical accumulation of harmful mutations occurs, the population dies out – this phenomenon is known as the Meller ratchet.
To some extent, a cancer cell can be considered a separate unicellular organism, it is not for nothing that tumor cells can multiply indefinitely "in vitro". In this sense, they can be likened to the simplest single–celled higher organisms - amoebas, in which there is no sexual process. And an additional copy of the genome for cancer cells is like a spare wheel for a car, since it allows them to "drive", i.e. survive and divide, even if fatal mutations have occurred in the main copy.
A group of scientists from the UK, USA and Belgium using computer modeling proved that natural selection really contributes to the doubling of the genome at a sufficiently high level of harmful mutations. By continuing research on human tumor samples as part of the TRACERx lung cancer program, they obtained data confirming this hypothesis.
The article by López et al. Interplay between whole-genome doubling and the accumulation of deleterious alterations in cancer evolution is published in the journal Nature Genetics.
It turned out that when the genome doubles in cancer cells, there are more mutations in them, but this does not prevent the cells from living and reproducing further. Analysis of the results of positive and negative selection before and after genome doubling allowed scientists to identify genes that both promote and prevent the progression of cancer. According to the researchers, the results of this work open up the possibility of creating new anti-cancer drugs aimed at viable cancer cells with a doubled genome.
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