Cancer stem cell and niche.

Recent research on cancer has generated a new model for cancer growth-cancer stem cell model. This model can explain the inefficiency of conventional therapy. Tumor tissue, like normal tissue, is continuously repopulated from pools of self-renewing stem cells growing in a "niche", which is made up of a specialized vascular bed of endothelial cells, associated cells of mesenchymal origin and extracellular matrix components. In this review, we will introduce the models of cancer development, the roles of stem cells in tumor progression, the components of niche which affects the cell fate of cancer stem cells (CSCs), their different regulatory factors, as well as the clinical implication of CSCs in cancer treatment.