Scientists announced the discovery of cancer stem cells

Three independent groups of scientists simultaneously reported the discovery of so-called cancer stem cells - small groups of cells that are responsible for the growth of cancerous tumors. The isolation of such cells changes not only the understanding of the mechanism of development of malignant neoplasms, but also the approach to their treatment. Two works devoted to this topic were published on August 1 in the journal Nature and another one - in the journal Science.

Thus, the hypothesis has been confirmed that the ability of cancerous tumors to resume their growth after a long period of remission is based on the existence of a small group of cells that can “wait out” the effects of both chemotherapy and radiation therapy in a dormant state, in order to then begin active division and launch the same process in other types of cancer cells, initiating the re-development of the disease.

The first assumptions about the existence of such a catalyst and, accordingly, the hierarchical nature of cancer cell growth appeared back in the 1990s during a study of the development of leukemia in mice, but they have not yet been confirmed using the example of malignant tumors developing in various tissues of the body.

All the research teams that reported their findings used genetic marking techniques to track the processes occurring in tumors and how different types of cells are involved. Each team had its own objects of study.

So, a team led by biologist Luis Parada of the University of Texas Southwestern Medical Center (UTSMC) in Dallas, whose work was published in Nature, focused on glioblastoma, a type of brain cancer. They hypothesized that genetic markers found in healthy adult neural stem cells might be similar to those found in glioblastoma stem cells. Based on this assumption, the authors actually found a few cells in the tumor with these markers, while the rest of the tumor cells did not.

Further studies showed that standard chemotherapy killed all cells except the labeled ones, after which the tumor growth resumed, with the labeled cells giving rise to all the others. When the authors managed to suppress the division of the labeled cells, the tumor actually disintegrated into fragments that did not become the basis for the development of new glioblastomas.

A group led by Cédric Blanpain from the Free University of Brussels (Université Libre de Bruxelles, ULB), whose work was also published in Nature, studied skin cancer, and all tumor cells were used as objects of study. They managed to find out that cancer cells differ in their division scenario - some of them can divide a limited number of times, and some, and these are the very same stem cells, can divide indefinitely. It turned out that when cancer becomes aggressive, the tumor mostly forms stem cells capable of unlimited division, and not other types of cells. According to Blanpain, this discovery may be the key to a new strategy for treating cancer at early stages - instead of removing stem cells, they are transformed with the help of therapeutic action into another type of cell with a limited ability to divide.

And finally, a third group of researchers led by Hans Clevers of the Hubrecht Institute in Utrecht, the Netherlands, whose work was published in Science, focused on the cells that form intestinal adenomas, the precursors of intestinal cancer. They first bred a line of mice, which the authors called "confetti mice" - the rodents carried a genetic marker that, when exposed to a certain substance, caused intestinal cells to produce molecules of four colors, depending on what cells they originated from. The scientists managed to obtain tumors that were stained with the same color, but consisted of different types of cells, which shows that they all originated from one source - a stem cell. A change in the color of these cells led to the appearance of many cells of a similar color, which confirmed the version that stem cells produce all the others.

As Parada noted, it is too early to say that the new data obtained is applicable to all types of cancer. But if further research proves that this is the case, the methods of fighting cancer will change dramatically. In particular, the assessment of the effectiveness of chemotherapy will change - doctors will focus not on stopping the growth or even the complete disappearance of the tumor, but on whether the cancer stem cells died as a result of the treatment.

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