[Angiogenesis--principles and significance in urologic tumors]

Physiologically, angiogenesis in adults is a controlled process which plays a role, for example, in wound healing. Pathological angiogenesis is observed in tumor formation and represents a multifactorial process, in which specific angiogenic factors, as well as growth factors, extracellular matrix proteins and cell adhesion molecules are involved. Tumor growth is characterized by an imbalance in favor of angiogenic over angiogenesis-inhibiting factors. Some of the most frequently examined angiogenic factors are vascular endothelial growth factor, acidic/basic fibroblast growth factors and the platelet-derived endothelial cell growth factor. The most important angiogenesis inhibitors are angiostatin and thrombospondin. To date, the clinical relevance of tumor angiogenesis has been shown for several human tumors. For most urological tumors, the grade of tumor vessel formation, measured as microvessel density, has been associated with metastases, tumor growth and clinical course. The prognostic value of this feature of malignant growth seems to be higher than that of most of the classical and newer prognostic factors. Systematic investigations of tumor angiogenesis are becoming increasingly relevant for diagnostic and therapeutic strategies and offer opportunities for the development of new specific therapeutic approaches in clinical oncology.