Cancer Stem Cells: On the Verge of Clinical Translation

Researchers have long studied malignant tumors using experimental techniques that assume that cancers are composed of identical cells; however, growing evidence indicates that cancers are composed of functionally heterogeneous cells maintained by a stem cell-like population. Identification of tumor-initiating, or cancer stem cells, has been largely guided by principles established for normal stem cells. Cancer stem cells must be capable of initiating tumors when transplanted into immunodeficient mice, and the resulting tumors must replicate the heterogeneity of the original tumor. Demonstration of the ability to self-renew, a key feature of stem cells, is achieved through serial passage of tumors in xenohosts. Given their potential roles in tumor initiation, maintenance, and metastasis, the impact of cancer stem cells on the practice of medicine is likely to be profound.