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Table 1 Phenotypic characteristics of breast cancer stem cells

From: Breast cancer stem cells: implications for therapy of breast cancer

Factor Characteristics Reference(s)
Cell surface markers that are expressed by putative breast cancer stem cells
   ABCG2 ABCG2 (ATP-binding cassette G2) is a class of drug transporters capable of pumping cytotoxic drugs out of the cell. [6]
   CD44 CD44 is involved in cellular adhesion, motility, and metastases. [34, 35]
   CD10 CD10 is a common acute lymphoblastic leukaemia antigen that is overexpressed on many tumours. [39]
   EpCAM/ESA Epithelial cell adhesion molecule/Epithelial surface antigen is expressed on mammary tissue and tumours. [39]
   CD29 (β1-integrin) CD29 is a membrane receptor involved in cell adhesion and metastatic diffusion of tumour cells. [9]
   CD49f (α6-integrin) CD49f is involved in basal and endothelial cell distribution and is a candidate stem cell marker. [39]
   CD133 (prominin-1) CD133 is a cell surface glyoprotein with an unknown function in cancer stem cells and its expression is documented for various types of cancer. [116, 117]
   ALDH1 Aldehyde dehydrogenase-1 plays a role in the differentiation of stem cells and its activity predicts poorer clinical outcomes. [112]
   CXCR4 CXCR4 is a chemokine receptor involved in metastasis and its expression is increased in mammospheres. [44, 45]
   ER Oestrogen receptor is expressed on breast cancer cells, mammary progenitors, and breast cancer stem cells. [54, 59]
Signalling pathways that play a role in cancer stem cells
   Delta/Notch pathway This pathway is involved in cell fate development and is expressed in stem cells and early progenitor cells. [60]
Notch-4 Notch-4 plays a role in mammary development and its overexpression has been shown to promote mammary tumours. [45, 60, 61]
   Wnt signalling pathway This pathway is involved in stem cell self-renewal and its overexpression can lead to epithelial and mammary tumours. [27, 63]
β-catenin β-catenin is a downstream target of the Wnt pathway. A pro-oncogenic role has been described. [63]
   Hedgehog/Patched pathway This pathway is involved in embryonic growth and cell fate determination. [64]
PITCH A receptor for the Hedgehog signalling family, PITCH has been connected to early embryonic tumourigenesis. [64]
EGFR Epidermal growth factor receptor signalling has been found to be upregulated in breast cancer stem cells and may be required for mammosphere formation. [77, 111]