[Angiogenesis in tumors. Part I. Its role in the determination of biological characteristics of tumors; factors controlling the onset and development of angiogenesis].
The tumor stroma gains increasing attention in recent years. Angiogenesis (AG) is defined as formation of new vessels from the endothelium of the preexisting vasculature. The vascular bed does not only provide supply of nutrition factors and oxygen as well as elimination of metabolic waste, but the neo-formed vessels represent also a gate for lymphogenous and hematogenous metastatic spread of the tumor. For tumor growth beyond the size of several mm, AG must be started to form vascular supply of tumor cells. After the switch to angiogenic phenotype, the tumor starts to exhibit rapid, almost exponential growth. AG is a complex process, involving degradation of the basement membrane of preexisting vessel, proliferation of endothelial buds or solid strands towards the angiogenic stimulus, maturation of endothelial cells with formation of a luminized capillary, connection of such capillaries with creation of vascular loops, and finally formation of a functional vessel, surrounded by basement membrane and pericytes. The most intensive AG is observed at the periphery of the tumor. AG is regulated by numerous angiogenic and anti-angiogenic factors, which can be synthesized and released by tumor cells themselves, stromal elements, as well as inflammatory cells, namely macrophages. The issues of regulation of AG and importance of AG for tumor growth, progression and metastasis are discussed.
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Fingerlandův ústav patologie, Fakultní nemocnice, Hradec Králové.
D000818:Animals; D016228:Endothelial Growth Factors / Q000502:physiology; D006801:Humans; D008222:Lymphokines / Q000502:physiology; D009369:Neoplasms / Q000098:blood supply* / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors