Breast Cancer Stem Cells: Tumourspheres and Implications for Therapy

Abstract

Breast cancer is a heterogenous disease, composed of tumour cells with differing gene expressions and phenotypes. Tumour heterogeneity has several important consequences for breast cancer including: (i) making classification by morphological and expression analysis more difficult because of the diversity within single tumours with the consequence that the majority of cells of the tumour will dominate this classification whether or not these cells are critical for diagnosis or treatment; (ii) treatments may fail to eradicate tumours simply by failing to eliminate one of the cell subtypes within the tumour; and (iii) differing abilities of the cell subtypes for dissemination and metastasis. Recently, a rare subpopulation of cells within tumours has been described with the ability to initiate and sustain tumour growth, to resist traditional therapies and to allow for secondary tumour dissemination. These cells are termed tumour-initiating cells or cancer stem cells, or alternatively, in the case of breast cancer, breast cancer stem cells. The therapeutic targeting of these cells has the potential to eliminate residual disease and may become an important component of a multi-modality treatment of cancer. Presented here is an investigation into: (i) ways to functionally and phenotypically identify breast cancer stem cells; (ii) the role of breast cancer stem cells in disease from both clinical samples and using xenograft assays; and (iii) the potential to target these cells.