[Homeostasis of adult stem cells and carcinogenesis]

Treatment of malignant tumors using radiotherapy, chemotherapy, immunosuppressive drugs required to recover bone marrow transplant by the donor bone marrow or purified adult stem cells. During the next 1-15 years of follow up of these patients compared with healthy individuals of the same age increases the risk of multiple malignancies. It used to be attributed to the influence of therapeutic effects. However, it is revealed that some of the cells and the stroma of the secondary tumors are composed of descendants of transplanted stem cells. This indicates the important role of stem cells in tumor growth. This is also evidenced by numerous studies showing that adult stem cells from both mice and humans multiplied in vitro, after transplantation into the body give the sarcoma, cancer foci and other types of malignant growth. In this, malignant growth is most intense in the presence of focal chronic inflammation. No less than the experimental data, including those obtained in humans suggest that the transplanted stem cells actively colonize stroma of tumor tissue, stimulating the growth of the tumor and its metastasis. The human condition of survival is the presence of rigid homeostatic control mechanisms of low numbers of stem cells in the body and the limit their division, even in areas of regeneration. After the transplantation of stem cells their number in the bloodstream and, consequently, in the pathological foci of regeneration, increases in many dozens of times--this level can not be achieved by the organism itself. This leads to a sharp increase in the rate of regeneration of tissues, which creates conditions for amplification of malignant growth.