Should be the term actually refers to any type of chemotherapy drug treatment in the cells brought to the death or prevented from growing. The pathogen can be just as cancer cells. In another sense, therefore, antibiotics are regarded as "chemotherapy".
Today the term is however used almost exclusively for the reduction or destruction of tumors with so-called cytotoxic drugs. The compromise also colloquially referred to as cell poisons cancer cells essential substances in their function: Further divisions are stopped and removed the damaged cells from the patient's body.
Prevention of cell division
The treat tumors cytostatics used to achieve this in different ways (more on that in the chapter on "substances"): Some place in the genetic information directly - they are similar, for example, natural building blocks of genetic material DNA (German: DNA for deoxyribonucleic acid - see picture, a new screen window ). They are incorporated in the division of tumor cells instead of the "real" molecules. Thus, the genetic information is destroyed. If anything, nor is daughter cells, so they continue to grow no more.
Other cytostatic drugs inhibit the duplication of genetic material and the uniform distribution on two new cells during cell division - they stop enzymes that are involved in the structure of DNA, or "glue" the coil of DNA (see figure, a new screen window).
Some cytotoxic drugs do not work on cell division, but on the normal function and metabolism of tumor cells. To block auxiliary molecules that are important for the production of proteins. So they stop the supply of "building material" for the cell, ie structure of proteins, enzymes and other substances needed by the cancer cell to grow.
Programmed cell death: Why is not just toxic chemotherapy?
Tumor cells "explode" when chemotherapy is not easy. This would take patients also did not: An extensive tissue destruction, called a tumor necrosis or tumor lysis would poison her body as after a burn or a severe infection with cell debris and degradation products literally: the kidneys, blood clotting and the immune system would be overwhelmed.
Although it is mainly used in cancer patients with large tumors are rapidly reduced by the treatment, some necrotic. The currently used therapeutic regimens targeted but mainly to tumor cells to prevent the uncontrolled parts first.
Such damaged cells become inactive and are detected via an endogenous control mechanism and selectively degraded. Their remains recovered on the metabolism, just as he did with all aged or become functionless cells usually does well. The technical term for this is apoptosis, this mechanism is also known as programmed cell death.
The success of chemotherapy is therefore rarely seen overnight: it takes several days or even weeks, before we can assess the response of a tumor safely.
On the topics apoptosis, impaired cell aging and cell death is disturbed intensively researched. The number of scientific publications it is in the thousands, even if one considers only German-language article (as an example an overview of work at the German Cancer Research Center in ....
Effect: Non-cancer-specific
Lexicon
Differentiation (grading): a measure of maturity of the tumor cells. Well "differentiated" tumor cells are normal, mature cells relatively similar."Undifferentiated" tumor cells have hardly similarities with the tissue of origin.
Most cytotoxic drugs intervene in cell division or metabolic processes that play not only in tumor cells, but in all cells play an important role. You are not cancer-specific effect.
Nevertheless, they damage tumor cells almost predominantly far more than healthy tissue. The reason lies in the biological behavior of cancer cells: The majority of normal cells is mature, the technical term is called differentiated. In most tissues, cell division takes place just as much as is necessary for the preservation and regeneration.
The healthy cells instead fulfill their tissue-specific tasks - say they are "grown up".Where there is no cell division, cytostatics can not even attack the genetic material.Where no anabolic metabolism, the production of daughter cells prepared, the corresponding processes are not disturbed.
The rapidly growing tumor tissue, however, is marked by a high proportion of immature and undifferentiated cells (in tumor diagnosis: degree of differentiation or grading) - they are much more sensitive to chemotherapy.
Affected by cytotoxic drugs but also healthy tissue, which divide as fast as cancer cells: These are about the mucous cells in the mouth and digestive tract, which must be replaced due to high mechanical stress constantly. Also affected are the root hair cells, blood cells and to a lesser extent, other rapidly regenerating tissues. This impairment explains part of the typical side effects of many chemotherapy regimens (more on that in the "side effects").
How exactly does the biological behavior of tumor cells differs from that of healthy tissue is the subject of intense research. Some tumors have been found so-called stem cells, of which only runs out of growth, while the rest of the cells is not involved.Whether that is true for all cancers and in every phase of tumor growth, for most cancers can not be assessed. What consequences it would have for the planning of chemotherapy, if there is such a "division of labor" would be in each tumor tissue, is also still unknown.
Treatment planning: What is the role of tumor biology?
In order to make cancer cells as directly as possible and protect healthy cells as much as possible, it is important to know as much about the biological properties of a tumor. The processing of tissue samples for biopsy or surgery under the microscope and by molecular biological methods is one reason the standard in cancer diagnosis. These studies provide important information about the behavior of cancer cells, their growth rate, the degree of deviation from normal tissue and thus the degree of malignancy. The results facilitate treatment planning. The underlying tests are intensive research ever closer and more meaningful.
Tests are usually right sensitivity with which the response of a tumor to different medications before starting treatment to be tested, have lived up to expectations so far not met (more on that in Chapter "chemotherapeutic sensitivity and resistance").
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