The significance of cancer stem cells in oncogenesis and immunotherapy of tumors
Summary. According to the modern theories of oncogenesis it is supposed that genetic, epigenetic and transcriptional changes in normal cells lead to its oncotransformation into cancer cells, which are characterized by stable proliferation, invasion, metastasis, replication immortality, angiogenesis and also resistance to growth suppression and apoptosis, which altogether determine characteristics of cancerous growth. The analyses of genetic variety and antigen composition of primary tumors showed significant intratumoral heterogeneity of different types of cancers, which are consisting of mixture of genetically different sub clones of cells of primary heterogenic tumor, among which only one or perhaps several types of cells can develop metastasis, recurrent growth of the tumor or induce the tumor in experiment, which had become the basis for expression of the separate cell clone — cancer stem cells (CSC) possessing the features of normal stem cells and the tumor as well. In this review the detailed analyses of major data concerning the features of CSC is presented — these are large migration ability, chemo and radio resistivity, ability to induce the tumor growth in experiment, differential mimicry, ability to infusion with host cells, angiogenesis and induction of vessel growth. It is noted that there is no common view on the nature of CSC and the attempt to divide it in several subpopulations is pointed out: the tumor initiating stem cells, tumor progenitor cells, resistant to chemotherapy tumor stem cells. Each of this subpopulations has ability to self reproduction or transformation into one another. The detection of specific oncogenic or embryonic proteins on CSC is required not only to characterize and verify the types of CSC in histologically different tumors, but also for making a prognosis of treatment results. The development of innovation biotechnological drugs like monoclonal antibodies or oncovaccines targeting the CSC will allow to improve the strategy of combined treatment in patients with malignant neoplasms.
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