Cancer stem cells and response to therapy.

The cancer stem cell (CSC) model states that cancers are organized in cellular hierarchies, which explains the functional heterogeneity often seen in tumors. Like normal tissue stem cells, CSCs are capable of self-renewal, either by symmetric or asymmetric cell division, and have the exclusive ability to reproduce malignant tumors indefinitely. Current systemic cancer therapies frequently fail to eliminate advanced tumors, which may be due to their inability to effectively target CSC populations. It has been shown that embryonic pathways such as Wnt, Hedgehog, and Notch control self-renewal and cell fate decisions of stem cells and progenitor cells. These are evolutionary conserved pathways, involved in CSC maintenance. Targeting these p.