Abstract

Recent advances have highlighted extensive phenotypic and functional similarities between normal stem cells and cancer stem cells. This raises the question of whether disease therapies can be developed that eliminate cancer stem cells without eliminating normal stem cells. Here we address this issue by conditionally deleting the Pten tumour suppressor gene in adult haematopoietic cells. This led to myeloproliferative disease within days and transplantable leukaemias within weeks. Pten deletion also promoted haematopoietic stem cell (HSC) proliferation. However, this led to HSC depletion via a cell-autonomous mechanism, preventing these cells from stably reconstituting irradiated mice. In contrast to leukaemia-initiating cells, HSCs were therefore unable to maintain themselves without Pten. These effects were mostly mediated by mTOR as they were inhibited by rapamycin. Rapamycin not only depleted leukaemia-initiating cells but also restored normal HSC function. Mechanistic differences between normal stem cells and cancer stem cells can thus be targeted to deplete cancer stem cells without damaging normal stem cells.

1. Howard Hughes Medical Institute, Life Sciences Institute, Department of Internal Medicine, and Center for Stem Cell Biology, University of Michigan, Ann Arbor, Michigan 48109-2216, USA
2. Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109-2216, USA
3. Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, California 90095-1735, USA

Correspondence to: Sean J. Morrison¹ Correspondence and requests for materials should be addressed to S.J.M. (Email: seanjm@umich.edu).

Received 1 October 2005 | Accepted 1 March 2006 |

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