Discussion of cancer stem cells as the cause of tumors
Do tumors develop their own stem cells that lead to constant cancer outbreaks? After three studies in August provided new evidence for the theory of cancer stem cells as the cause of recurrent cancer, there was an intense discussion among experts about the potential of this approach, which has been known since the late 1990s. The previous cancer therapies may have to be adjusted in principle.
Cancer often returns after supposedly successful surgery, chemotherapy or radiation therapy. The three independent studies by researchers from the Université Libre de Bruxelles (Belgium), the Hubrecht Institute in Utrecht (Netherlands) and the University of Texas Southwestern Medical Center (USA) suggest that cancer stem cells are responsible for the onset of cancer . The treatment should therefore not only be aimed at eliminating cancer cells, but also cancer stem cells. The studies were published in the specialist magazines "Nature" and "Science".
Cancer stem cells source of tumor growth The results of the three current studies provide relatively clear evidence that "in certain brain, skin and intestinal tumors, cancer stem cells are the source of tumor growth", the scientific journal Science reported in an overview article in early August. The studies by researchers from the United States and the Benelux have sparked heated discussions because they contradict the previous assumption of a monoclonal cancer development theory in which all cancer cells are the same and every single cell with the ability to divide can be the starting point for new tumors. Cancer stem cell theory assumes that there is a hierarchy of cancer cells. The cancer stem cells are to be distinguished from the other cancer cells and are essentially responsible for the re-outbreak of supposedly overcome cancer.
Confirmation of the cancer stem cell hypothesis in the mouse model According to their article in the journal Nature, the scientists led by Cédric Blanpain from the Belgian Université Libre de Bruxelles came to the conclusion that "most of it." Tumor growth is triggered by a few cells, which in some ways resembled the stem cells of healthy skin. ”Normal human stem cells can reproduce all kinds of other cell types, but the so-called cancer stem cells serve to grow cancer cells. The Dutch researchers led by Hans Clevers from the Hubrecht Institute in Utrecht have examined the cancer stem cell hypothesis as part of their study and found in "mouse models direct, functional evidence for the presence of stem cell activity in primary intestinal adenomas, a precursor of colorectal cancer" the specialist magazine "Science". The recognized cancer specialist at the University of Houston, who was not involved in the studies, Jeffrey M. Rosen, also sees the current studies as confirmation of the cancer stem cell theory.
Cancer stem cells cause brain tumors to break out The most unequivocal evidence for the existence of cancer stem cells came from the study also published in the journal "Nature" by evolutionary biologist Luis Parada from the University of Texas Southwestern Medical Center. Parada and colleagues had injected mice with labeled cancer cells from gliomas (brain tumors). The resulting tumors in the brain of the mice were treated with chemotherapy. Although the majority of the treatment was successful and the tumors could be removed, the cancer usually broke out again relatively shortly after the treatment. According to the results of the US researchers, a “relatively calm part of the endogenous glioma cells, with properties similar to those in cancer stem cells, survived in the mice.” According to Luis Parada, these could be the “real enemy”. The cancer stem cells are "responsible for ensuring long-term tumor growth through the production of highly proliferative cells," said the US researcher. The first non-representative studies in humans would have provided comparable results.
Adaptation of cancer therapies necessary? In all three studies to test the cancer stem cell hypothesis, the scientists used genetic cell labeling techniques to track the proliferation (proliferation) of certain cells in the growing tumors. The cancer stem cells determined in this way survive chemotherapy and then reproduce new cancer cells that could continue to multiply. Successful treatment would also have to localize and eliminate cancer stem cells. However, it will only be necessary to check whether the cancer therapies need to be adapted accordingly in further studies on humans. It also remains unclear how cancer stem cells can be killed without doing too much harm to the organism. However, the scientific discussion in cancer research is now increasingly moving in a new direction. (fp)
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