Cancer stem cells - A therapeutic target?

Cancer stem cells (CSCs) form a highly tumorigenic core in most human tumors. Although there is no consensus regarding CSC phenotype from different tumor types, CSCs from different cancers share a primitive undifferentiated nature, including a capacity to expand and differentiate, albeit aberrantly, into the major cell types observed in the corresponding tumor. This review focuses on the development of therapeutics targeting CSCs, for which new assays that replace those reporting the inhibition of cell division and rapid tumor shrinkage will be required to account for the quiescent nature and properties of CSCs. The inhibition of signaling pathways related to the stem cell nature of the CSCs may appear an attractive target for novel therapeutics, but these targets could result in significant unwanted off-target effects against essential healthy tissue stem cells. Instead, the ideal therapies targeting CSCs will be directed against functions that contribute to the oncogenic nature of CSCs relative to healthy stem cells, an altogether more challenging task.