Cancer stem cell definitions and terminology: the devil is in the details

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The cancer stem cell (CSC) concept has important therapeutic implications, but its investigation has been hampered both by a lack of consistency in the terms used for these cells and by how they are defined. Evidence of their heterogeneous origins, frequencies and their genomic, as well as their phenotypic and functional, properties has added to the confusion and has fuelled new ideas and controversies. Participants in The Year 2011 Working Conference on CSCs met to review these issues and to propose a conceptual and practical framework for CSC terminology. More precise reporting of the parameters that are used to identify CSCs and to attribute responses to them is also recommended as key to accelerating an understanding of their biology and developing more effective methods for their eradication in patients.

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Figure 1: Models of cancer stem cell evolution: perturbation of the normal differentiation hierarchy.
Figure 2: Proposed model of cancer stem cell evolution.
Figure 3: Effects of therapies.


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The Year 2011 Working Conference on Cancer Stem Cells was supported by a Cancer Stem Cell Grant of the Medical University of Vienna, Austria. The authors would like to thank S. Sonnleitner and K. Krassel for their helpful technical support. H.E.J. was supported by the EU 6th FP to MSCNET (LSHC-CT-2006-037602). M.C. is supported by a Fellowship from the Scottish Funding Council (SCD/04) and J.V.M. by the NIHR Biomedical Research Centre Funding Scheme, UK.

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Correspondence to Peter Valent or Connie Eaves.

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Supplementary information

Supplementary information S1

Classification of therapies according to their effects (PDF 427 kb)

Supplementary information S2

Overview of Mechanisms of CSC Resistance to Therapy and Strategies to Overcome Resistance (PDF 199 kb)

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