Biomedicine

Looking for Cancer Stem Cells

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Science  13 Apr 2007:
Vol. 316, Issue 5822, pp. 175
DOI: 10.1126/science.316.5822.175a

The intense interest in stem cell research has helped to revive the cancer stem cell hypothesis, which postulates that tumor cell growth is driven by a small population of malignant cells that have the ability to self-renew and to differentiate—a capacity that is shared with normal tissue stem cells. The idea is attractive because it suggests that drugs could be designed to target cancer stem cells selectively, if and when these cells are identified. Although the stem cell origin of leukemias is now widely acknowledged, the role of stem cells in solid tumors has been more contentious. Shipitsin et al. performed a comprehensive molecular characterization of two classes of cells purified from human breast cancer: one class expressed a cell surface marker (CD44) previously associated with high tumorigenicity and stem cell-like properties, and the second class expressed a marker (CD24) previously associated with low tumorigenicity and a more differentiated state. The CD44+ breast cancer cells were found to express many genes in common with progenitor cells in normal breast tissue, and the abundance of these cells in the tumor appeared to correlate with decreased patient survival. However, the CD44+ and CD24+ cells within individual breast tumors showed genetic differences, a finding that does not fit neatly with the simplest version of the cancer stem cell hypothesis. An alternative model is that many cancer cells retain the capacity to adapt to changing conditions, whether this means reverting to a more primitive, stemlike state or evolving into a more differentiated state. — PAK

Cancer Cell 11, 259 (2007).

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