Cancer therapy causes cancer?

Cancer therapy causes cancer?

(18.08.2010) Therapies with the use of the „PUMA protein“ The targeted destruction of defective cells may favor the occurrence of further cancers at a later date.

Researchers at the Biozentrum at the Medical University of Innsbruck are now in the specialist journal „Genes & Development“ have come to the conclusion that cancer therapies in which activated programmed cell death is induced by stimulated endogenous functions may be the cause of later cancers. For example, their study explains why, for example, children who have been cured of leukemia often develop other cancers 20 or 30 years later, emphasized Andreas Villunger, Head of the Development Immunology Section at the Medical University of Innsbruck. „Around 15 percent of new cancer cases are now new tumor types that occur in cancer survivors.“, what loud Villunger „with the aggressive apoptosis-inducing therapy, thus the purposeful destruction of faulty cells, with the first cancer illness“ ... The therapies involved use a process that is triggered by the protein "p53" (also called "guardian of the genome").

The protein registers damage in the cells and sends other proteins as helper, the latter differing from proteins that repair, inhibit or destroy damaged cells. The cancer therapies used in this case use the activated for the destruction of cells „PUMA protein“, to kill the cancer cells in the body. The „Show experiments with leukemic mice“ however, „that precisely this controlled cell death itself can promote the development of cancer“, so Villunger.

The researchers eliminated in the framework study by the study „p53“ triggered protection mechanism and actually expected, „that these cells are now highly susceptible to tumor formation in vivo when exposed to harmful radiation, "says Villunger „Genes & Development“. However, in contrast to the expectations of the scientists, no tumor formation could be detected under irradiation, especially in those lymphocytes without "PUMA" protein. In control groups with intact "p53“-Protective mechanism were after several, genome-damaging radiation, however, clearly tumor formation to recognize ...

Villunger and his team conclude that tumor formation after cancer therapy is triggered by the revision of bone marrow stem cells. When combating cancer with the help of radiation (radiotherapy), the cells take so much damage that the "PUMA protein" is activated and kills the cells. However, about 90 percent of the affected blood and stem cells die in the process. Subsequently, the few surviving stem cells have to repair the resulting DNA damage and renew in parallel dead blood cells. "This dual task puts the stem cells under great pressure during cell division, which can again cause cell damage," said the immunologist Villunger. Since stem cells, without the PUMA protection mechanism, mostly survived the cells after irradiation and then used self-healing, more stem cells were used and the individual cell was not under comparable stress. The result: error-free cell division.

As a consequence of the existing forms of therapy, which have been practiced successfully for years and have already saved the lives of countless people, the treatment of patients should be handled with care or moderation. Otherwise it is to be feared that with the treatment of a current illness the cornerstone for later tumor building is laid. (Sb)

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Picture: Rolf van Melis