1. ¹Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Palo Alto, California, USA
2. ²Department of Pathology, Stanford University, Palo Alto, California, USA

Correspondence: Christopher Y. Park, Institute for Stem Cell Biology and Regenerative Medicine and Department of Pathology, Stanford University, 1050 Arastradero Road, Palo Alto, California 94305-5542, USA. E-mail: cypark@stanford.edu

Received 3 September 2008; Accepted 21 October 2008; Published online 9 December 2008.

Abstract

Cancer stem cells (CSCs) are defined by their ability to (i) fully recapitulate the tumor of origin when transplanted into immunodeficient mouse hosts, and (ii) self-renew, demonstrated by their ability to be serially transplanted. These properties suggest that CSCs are required for tumor maintenance and metastasis; thus, it has been predicted that CSC elimination is required for cure. This prediction has profoundly altered paradigms for cancer research, compelling investigators to prospectively isolate CSCs to characterize the molecular pathways regulating their behavior. Many potential strategies for CSC-directed therapy have been proposed, but few studies have rigorously demonstrated their efficacy using in vivo models. Herein, we highlight recent studies that demonstrate the utility of CSC-directed therapies and discuss the implications of the CSC hypothesis to experimental design and therapeutic strategies.