The Cancer Stem Cell Niche
Tumors are heterogeneous and composed of cells with different phenotypic, genetic, and functional features. In some tumors, a subset of cells can recapitulate the primary tumor upon serial transplantation into immunodeficient mice. These rare highly tumorigenic cells are often called cancer stem cells (CSCs) based on their ability to self-renew and differentiate into bulk tumor cells, giving rise to tumor tissue that recapitulates the heterogeneity seen in the primary tumor. As CSCs efficiently propagate malignancy, their therapeutic targeting holds promise for cancer eradication. However, several studies have shown that CSCs are refractive to standard therapies. Akin to normal stem cells, CSCs are believed to reside in a specialized microenvironment, or niche, which provides cues for the maintenance and propagation of CSCs. Recent studies have implicated an important role for the niche in mediating the treatment resistance of CSCs. In this chapter, we will review the current knowledge on the CSC niche and its contribution to tumorigenesis.
