Association between cancer stem cell-like properties and epithelial-to-mesenchymal transition in primary and secondary cancer cells

One of the theories on cancer stem cells (CSCs) states that these cells initiate most tumors and give rise to more-or-less differentiated tumor cells. Genetic signatures of CSCs are thought to predict tumor recurrence and metastases, thus, supporting the notion that CSCs may be metastatic precursors and induce epithelial-to-mesenchymal transition (EMT). In this study, we tried to examine the association between CSCs and EMT (using specific markers) in the mucoepidermoid carcinoma cell line YD15 and its derivative cell line YD15M (lymph node metastasis). Relative protein expression levels were analyzed by western blotting, flow cytometry, and immunofluorescence assays. In addition, cell cycle assay and aldehyde dehydrogenase (ALDH) activity assay were carried out. Under growth conditions, YD15M cells formed irregular spherical colonies consistent with a stem cell phenotype. YD15M cells demonstrated the low expression of E-cadherin and -catenin but high expression of vimentin than that in YD15 cells. In the metastatic cells (YD15M), the coexpression of vimentin and CD133 was detected. Weak proliferation based on cell cycle analysis and decreased PCNA expression was also observed. In addition, expression levels of ALDHA1, OCT4, and NANOG (CSC-like properties) were significantly increased in YD15M cells. Taken together, these findings should help to elucidate the interplay between EMT and CSC-like properties during metastasis and may provide useful information for the development of a novel classification system and therapeutic strategies against head and neck cancer.