Cancer Stem Cells Recent results have supported the cancer stem cells hypothesis in which tumors originate from tissue stem cells or their early progenitors and, as a result, produce tumors that retain stem properties. These properties drive tumorigenesis and differentiation that contributes to cellular heterogeneity. In breast cancers, a cell population of surface marker CD44 + CD24 -or low is highly tumorigenic. Aldehyde dehydronase(ALDH) positive cells are also powerfully tumorigenic and

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... marker can be poor prognostic factor in breast cancer patients. The number of cancer stem cells is very small, and is tightly controlled by the self-renewal pathway and the signals of their environment (niche). Epithelial-mesenchymal transition(EMT) is a key development program that is often activated during cancer invasion and metastasis. Although our understanding of the biology of these cancer stem cells remains rudimentary, the existence of these cells has implications for current conceptualization of malignant transformation and the treatment of cancer.