Tumor Vessel Associated-Pericytes

Abstract

In blood vessels, the crosstalk between vascular endothelial cells and mural cells (pericytes/vascular smooth muscle cells) play a central role in the regulation of vascular formation, maturation, remodeling, stabilization and function. During embryonic development as well as tumor growth and metastasis the process of angiogenesis is tightly regulated by vascular endothelial growth factor. Since vascular endothelial growth factor receptor is mainly expressed on endothelial cells, much effort has been made towards the context of endothelial cell biology in anti-angiogenic therapy. This endothelial cell-centred view has greatly ignored the fact that newly formed capillary networks stay in close contact to the surrounding tissue including peri-endothelial mural cells such as pericytes and smooth muscle cells. Pericytes play a pivotal role during vascular morphogenesis and stabilization. In this respect the interplay between endothelial cells and pericytes has drawn a lot of attention in the last decade. Today the mechanistic and molecular analysis of pericyte physiology is a rapidly growing field in biomedical research. It is highly appreciated that pericyte-mediated vessel maturation is a critical determinant of the therapeutic window in anti-angiogenic therapy. Due to the increasing evidence of the importance of pericytes in tumor biology this review summarizes the origin of pericytes, markers that determine, signaling pathways which are important in pericyte function and biology, as well as the role of pericytes during tumor progression.