Principles of premetastatic niche formation

The article is devoted to premetastatic niche as a complex term, including stromal cells, vessels, extracellular matrix and their changes during interaction with the primary tumor. On example of different malignant tumors authors describe as primary tumor through tumor exosomes prepares certain organs-recipients to metastatic clone implantation. In the area of premetastatic niche under the influence of tumorous exosomes polarization of macrophages towards M2 type takes place. The cells are the main agents, providing survival as well as migration of tumorous cells. Affecting extracellular matrix, macrophages change the microcirculatory bed permeability. This mechanism is directed towards increase of its permeability to entrance of metastatic clone cells form vessels into premetastatic niche. Besides macrophages fibroblasts and polypotent bone marrow stem cells are also reprogrammed, that results in metabolism and local immunity changes at the place of future implantation. As a result, only when tissue of recipient-organ is prepared for contact with metastatic clone, their interaction take place with consequent formation of secondary tumor metastatic niche. Thus, this review describes pathogenesis of metastasis, different from its early understanding as spread of metastatic clone with lymph and blood. These peculiarities may in future have significant impact in practical medicine, Blockage of signal spread from primary tumor through exosomes is one of the promising directions in pathogenetic therapy of malignant tumors. Investigation of principles of premetastatic niche formation may become a theoretical substantiation for prophylaxis of metastatic disease and inhibition of micrometastasis to macrometastasis transformation.