06 September 2012

Target for oncologists: cancer stem cells

The "Koshcheeva needle" of a cancerous tumor

Ekaterina Pustolyakova, SB RASScientists from several laboratories located in different parts of the globe came to similar conclusions almost simultaneously: there are stem cancer cells that give rise to tumors and trigger the disease.

The assumption of their presence has existed for several years. However, only now it has received official confirmation – after the publication of articles in the journals Nature and Science. Perhaps a landmark event for humanity comments on the director of the Institute of Chemical Biology and Fundamental Medicine SB RAS Academician Valentin Viktorovich Vlasov.

Stem cells have been known for years. Their main difference from differentiated ones (differentiation is a property associated with the specialization of work, the ability to perform certain functions in the body: mechanical work – muscle cells, signal transmission – nerve cells, and so on), is that they can endlessly divide and turn into various types of differentiated cells. A few years ago, researchers suspected that there were cancer cells with stem cell abilities.

Cancer is a very complex phenomenon, it is not one kind, but a complex of diseases. There is a set of "abnormal" cells in the tumor to varying degrees, which differ in properties: they have mutations in various genes, gene regulation systems are disrupted. The diversity of cancer cells has been noted for a long time, and it has also become clear for a long time that it is one of the reasons why it is so difficult to fight cancer.

After all, if the cells are standard and identical, then acting on them with a substance toxic to them, you can kill them all. For example, in infectious diseases there is a specific agent, virus or bacterium. Therefore, such diseases are relatively easy to cure with the help of certain drugs.

With a cancerous tumor, this does not work, or rather, it turns out at the first stage of treatment, and then the neoplasm often grows again, and the cells in it are already less sensitive to the same drug. What kind of picture do therapists observe? A cancer patient has been admitted, the doctor begins to treat him using a chemical that kills cancer cells. After a session of such therapy, the patient seems to be recovering. However, after some time, tumor growth or the appearance of unfavorable cells in the blood is observed again - moreover, they are already with altered properties, and the medicine that helped the first time does not help a second time.

That is, after the death of the main part of the neoplasm, some cells remained resistant to the drug, and they multiplied. Sometimes secondary tumors occur many years after the first effective therapeutic procedure, that is, harmful cells were hiding somewhere, and did not manifest themselves for a long time. This, as well as a number of other observations, allowed us to assume that there are cancer stem cells that can endlessly divide and change. It has been assumed for a long time, and the term "cancer stem cells" has been used for several years, however, the final proof of their existence was obtained only recently by groups of researchers in different countries: several laboratories came to this conclusion in parallel.

What gives such knowledge to researchers and doctors? First of all, the direction in which you need to work. Until now, during treatment, believing that this way it is possible to eradicate the tumor, they tried to create drugs that act on cancer cells, which are found in large numbers in the patient. Practice has shown: at the same time, the struggle drags on and often becomes hopeless. Now it became clear – it is necessary to aim at infinitely multiplying stem cells, to break the Koshcheev needle. They will be destroyed – and the tumor will come to an end. Using modern approaches, it is possible to create drugs that act on specific cells. It is only necessary to find features in their structure in order to accurately catch them on the fly. And then it will become much easier to fight tumor diseases.

Where stem cancer cells come from in humans at all is difficult to say. Traditionally, it was believed that mutations in cells constantly occur in our body under the influence of a variety of factors. There are many genes working in them, whose work is coordinated. If you disrupt the functions of one, usually nothing terrible happens, because the cell has a number of protective mechanisms that fight the consequences of mutations that constantly arise. In addition, the human immune system is also on guard and kills the "wrong" cells.

However, in the presence of certain combinations of changes in several genes at once, a breakdown of regulatory systems will occur in the cell. Cancer will occur when harmful mechanisms start working at the same time, and the useful ability of protection will be disabled. A simple analogy: someone picks up the password to the computer. Guessing one sign will not achieve anything, however, the sign combination will start everything. And the most dangerous thing is if this happens to an infinitely dividing stem cell. In humans, such cells (normal, necessary for tissue renewal) are everywhere: in the blood, in the lungs, and in the liver .... All of them, when the functions of their genes are disrupted, can become dangerous. The study of cancer stem cells and the mechanisms of their formation will bring us new knowledge that is important both for understanding the functioning of the human body and for creating approaches to cancer prevention, diagnosis and therapy.

Portal "Eternal youth" http://vechnayamolodost.ru06.09.2012

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