Breast cancer stem cells: implications for therapy of breast cancer

The past decades have seen advances in the diagnosis and treatment of breast cancer. Despite this progress, breast cancer is still a leading cause of cancer-related deaths among women, with as many as 40% relapsing with metastatic disease [1]. Breast cancer survival rates have been shown to plateau after 7 to 10 years, whereas most cancer survival curves take between 2 and 5 years to plateau [2]. The length of time for the survival rate to plateau in breast cancer might indicate the involvement of a cell type capable of disease recurrence which is able to withstand primary treatment and reside in the body, often undetected, for prolonged periods. Interestingly, it has been shown that, of the 40% of patients with lymph node involvement who did not undergo surgical removal, only 15% had recurrence of disease [3]. This raises the point that immune system surveillance of tumours or other protective mechanisms of the body might be capable of controlling breast cancer relapses.Prominent in the breast cancer field has been the notion of the existence of a transformed population of cells with many of the properties of stem cells that may be responsible for the origin and maintenance of tumours. These stem cell-like cells, designated as cancer stem cells, represent a minor subset of cells in the tumour and are distinct from the more differentiated tumour cells. It is thought that these cancer stem cells may play an important role in cancer establishment, progression, and resistance to current treatments. Traditional cancer therapies are effective at debulking some tumours but often fail to produce long-term clinical remissions, possibly due to their inability to eradicate the cancer stem cell population. Therefore, novel treatments aimed at targeting the cancer stem cell population could find use in treating both primary and metastatic tumours.Therapies aimed at targeting cancer stem cells may prove clinically relevant in inducing long-term clinical remission of cancer. A va