Epithelial Mesenchymal Transition and Vascular Mimicry in Breast Cancer Stem Cells

Vasculogenic mimicry (VM), a newly defined pattern of tumor microvascularization differs from angiogenesis and vasculogenesis in its noninvolvement of endothelial cells, by which highly aggressive tumor cells can form vessel-like structures themselves, because of their high plasticity. The presence of VM has been shown to be strongly associated with a poor prognosis in several types of cancer, but biological features of tumor cells that form VM remains unknown. Human breast cancer, characterized by a group of highly heterogeneous lesions, is the most common cancer in women and one of the leading causes of cancer-related deaths worldwide. The epithelialmesenchymal transition (EMT) state in breast cancer has been associated with cancer stem cell (CSC) properties, self-renewal capabilities, resistance to conventional therapies, and a tendency for posttreatment recurrence. With increasing knowledge about cancer stem cell phenotypes and functions, they are implicated in VM formation. Studies also indicate that EMT is relevant to the acquisition and maintenance of stem cell-like characteristics and is involved in VM. This review discusses the correlation between CSCs, EMT, and VM formation with a focus on breast cancer. Also, the signalling molecules and pathways involved in VM and some recently defined direct VM targeting strategies in breast cancer are reviewed here.