Epithelial-Mesenchymal Transition Associates with Maintenance of Stemness in Spheroid-Derived Stem-Like Colon Cancer Cells

Despite earlier studies demonstrating characteristics of colon cancer stem cells (CCSCs) and the role of epithelial-mesenchymal transition (EMT) in tumor development, it remains controversial as to the relationship between CCSCs and EMT. In this study, in order to present an insight into this relationship in colon cancer, we developed HCT116 and HT29 sphere models, which are known to be the cells enriching cancer stem cells. Compared to their parental counterparts, spheroid cells displayed lower homotypic/heterotypic adhesion but higher in vitro migratory/invasive capacity, as well as higher tumorigenic and metastatic potential in vivo. The spheroid cells also demonstrated down-regulated E-cadherin and up-regulated α-SMA and Vimentin expression, which is the typical phenotype of EMT. In order to explore whether this phenomenon is associated to activation of Wnt/β-catenin pathway, we detected several key signaling molecules. Compared with their parental cells, HCT116 and HT29 spheroid cells demonstrated down-regulated expression of GSK3β, but up-regulated expression of Slug and Snail. And also, the up-regulation of nucleus β-catenin in spheroid cells indicated that the free β-catenin transferred from cytoplasm to cell nucleus. Our findings indicate that spheroid cells have the characteristics of colon cancer stem cells, and EMT may account for their stemness and malignancy. And persistent activation of Wnt/β-catenin pathway may play an important role in the EMT of CCSCs.