Functional role of solid tumor stem cells in disease etiology and susceptibility to therapeutic interventions.

Cancer stem cells (CSCs) are defined by their innate stem cell like properties and can be identified by specific markers that include antigens, molecules and signaling pathways. Like stem cells, CSC divide indefinitely giving rise to both more CSCs and differentiated cell progeny. CSCs can give rise to tumors that phenotypically resemble their origin, either morphologically or by expression of tissue specific genes. Tumors arise from a single cell, the CSC, but the cells that constitute the tumor are not identical to each other. Evidence of heterogeneous populations within a tumor has led to an investigation of the cellular hierarchy of cancers. This review gives an overview of cancer stem cells, from breast, cervical, lung, prostate, head and neck, glioblastoma, pancreatic and colorectal cancers and mechanisms implicated in tumor development and therapeutic interventions.