The Landscape of Circulating Tumor Cell Research in the Context of Epithelial-Mesenchymal Transition

The metastatic spread of cancer accounts for the vast majority of cancer-related deaths. It is mediated by tumor cells circulating in blood (called circulating tumor cells, CTCs), which escaped from their established niches. CTCs give a unique opportunity to look into the metastatic cascade and to study the molecular processes supporting the spread of tumor cells throughout the body. As current therapies are not sufficiently effective in treating metastatic disease, it is important to determine cellular and molecular features of cancer cells that "seed" new tumors in distant organs at early stages. In this review we focus on the role of the epithelial-mesenchymal transition program in providing a survival advantage to metastasizing tumor cells, especially CTCs, and put it in the context of clinical findings.