Angiogenesis and endocrine tumors

Endocrine tumors are characteristically hypervascularized. This property re calls that of normal endocrine tissues, which possess a dense and specializ ed capillary network. The cellular and molecular mechanisms of the angiogen esis process associated with endocrine tumorigenesis are poorly known. Most normal endocrine cells consistuvely express high levels of angiogenic fact ors, such as VEGF, which likely play an important role in the development o f the characteristic vascular architecture of normal endocrine tissues. Cli nical and experimental data suggest that a surexpression of such angiogenic factors is unlikely to be involved in the induction of the angiogenic proc ess associated with endocrine tumorigenesis. In contrast, according to some experimental observations, the loss of endocrine-specific anti-angiogenic factors may be required for the initiation of the angiogenic process and th e transition from endocrine hyperplasia to endocrine neoplasia. Such inhibi tory factors remain to be indentified and characterized. A better understan ding of the mechanisms of angiogenesis in endocrine tumors is important for the delineation of novel therapeutic strategies.