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. Author manuscript; available in PMC: 2012 Sep 21.
Published in final edited form as: Trends Pharmacol Sci. 2011 Apr 27;32(8):487–494. doi: 10.1016/j.tips.2011.03.010

Figure 1. Models of chemoresistance.

Figure 1

According to the stochastic model of tumor progression, drug resistance is due to a pre-existent or acquired mutation (mutated cells are represented by green nuclei) in any tumor cell (a). According to the CSC hypothesis, acquired resistance derives from CSCs (in red) which may be intrinsically resistant or mutated after chemotherapy (b). Mutations in non-stem cell clones are ineffective, since they cannot propagate the tumor. Constitutively resistant tumors are enriched of drug-resistant CSCs. Modified from [7] with permission from Macmillan Publishers Ltd: Nature Reviews Cancer © 2005.