The cancer stem cell-vascular niche complex in brain tumor formation.

The cancer stem cell (CSC) theory hypothesizes that a small subpopulation of cells within a tumor mass is responsible for the initiation and maintenance of the tumor. The idea that brain tumors arise from this specific subset of self-renewing, multipotent cells that serve as the locus for tumor formation, has gained great support as evidenced by recent advancements in the biology of breast and colon cancer. It is well established that recruitment of bone marrow-derived proangiogenic progenitor cells and angiogenesis are key events in the process of brain tumor formation; however, the orchestration of these events by the CSC population has only recently been unveiled. In this review, we first introduce the CSC theory and examine the functional development of the vascular niche, its purpose, constituents, and contribution to the development of the CSC-vascular niche complex. Through this discussion, we aim to shed light on the events that may be targeted for therapeutic intervention.