Cancer Stem Cells: From an Insight into the Basics to Recent Advances and Therapeutic Targeting

Figure 1

Theories of origin of cancer stem cells. There are three possible theories: (i) CSCs could have possibly originated either from normal stem cells when they underwent mutation or oncogenic transformation, (ii) from progenitor cells who also undergone mutations, and (iii) from the fully differentiated cells that undergone several mutations via dedifferentiation (curved black arrows indicate self-renewal, while the straight arrows indicate the expression promotion).