Cancer Stem Cell Quiescence and Plasticity as Major Challenges in Cancer Therapy

Figure 1

Cancer stem cell (CSC) properties and experimental methods for phenotypic and functional characterization of CSCs. (a) CSCs express cell surface antigens (CD133, CD34, and CD44) and signaling molecules (OCT4, NANOG, and SOX2) linked to a stem-like phenotype. CD: cluster of differentiation; OCT-4: octamer-binding transcription factor 4. (b) CSCs possess clonal properties and may be maintained in vitro for long intervals in serum-free medium. Under these conditions, they are able to form clonal tumorospheres. (c) CSCs present increased Hoechst efflux capacity compared to normal cells. Based on this property, they are designated as the side population (SP). (d) Multilineage differentiation (in the presence of serum) is another property of CSCs. Differentiation ability is verified by the decrease in the expression of stem cell markers accompanied by an increase in the expression of differentiation markers. Differentiated cells lose their tumorigenic potential. (e) CSCs at limiting dilutions are able to generate tumors after serial xenografting into immunocompromised mice. These tumors recapitulate the characteristics of the tumor from which CSCs were derived. Figure was constructed in part with objects from Servier Medical Art documents under license from Creative Commons Attribution 3.0 France (http://creativecommons.org/licenses/by/3.0/fr/legalcode).

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