Figure 1. Cancer stem cell properties and therapeutic resistance.

An illustration of a solid tumor depicts the cellular milieu, comprised of differentiated tumor bulk, a small number of CSCs, and tumor vasculature. The CSC niche provides cues that direct CSCs to undergo self-renewal to maintain the CSC sub-population, or differentiation to generate the tumor bulk. Conventional chemotherapeutic approaches target the tumor bulk, but due to their inherent chemoresistance, CSCs remain largely unaffected and potentially lead to tumor repopulation and/or metastasis. CSC directed therapeutics that target critical regulatory pathways in CSCs, such as Wnt, Notch and HH, have the potential to inhibit tumor repopulation and metastasis, resulting in tumor degeneration.