Surface markers of cancer stem cells in solid tumors

Cancer stem cells (CSCs) are a small subpopulation of cells within tumors with capabilities of self-renewal, differentiation, and tumorigenicity. Successful cancer treatment would need to eliminate CSCs. The CSCs can be identified and isolated by both CSC-specific cell surface marker expression and functional assay, such as floating spheres, and aldehyde dehydrogenase (ALDH) activity assay. However, lack of universal expression of surface markers limits their usage to identify CSCs. Here, we give a brief overview of the current known surface markers of CSCs and associated tumor types. Finally, the possible reasons for contradiction are discussed in these surface markers. In this review, I not only provide an overview of the current known surface markers but also highlight the importance of achieving maximal accuracy of a new marker.