Tumor Angiogenesis: A Focus on the Role of Cancer Stem Cells

Angiogenesis is the process of growth of new blood vessels. Tumor angiogenesis plays pivotal roles in tumor development, progression, and metastasis. The conventional notion of tumor vasculature is that new tumor blood vessels sprout from preexisting vasculature near the tumor; hence, tumor endothelial cells are derived from normal endothelial cells. However, recent evidence suggests that CD133‐positive cancer stem cells (CSCs) in glioblastomas generate tumor endothelial progenitor cells, which further differentiate into tumor endothelial cells. This chapter offers an overview of current knowledge on the role of CSCs in tumor angiogenesis. Furthermore, we discuss our recent discoveries related to human hepatoblastoma stem cells. Future efforts to elucidate the characteristics of tumor angiogenesis should enable the development of effective new anti‐angiogenic therapies