[Epithelial-mesenchymal transition induces cancer stem cell generation in human thyroid cancer cells in vitro]

Epithelial-mesenchymal transition (EMT) has been implicated in the initiation and conversion of early stage tumors into invasive malignancies and is associated with the "stemness" of cancer cells. The present study was designed to identify whether EMT induces cancer stem cell generation and tumor progression in human thyroid cancer cells in vitro.

FTC133 cells, as EMT-negative cells, were used for EMT induction by hypoxia-inducible factor-1α (HIF-1α) transfection. And EMT features were then examined by Western blot, immunofluorescent staining, invasion and proliferation assays. Moreover, stem-like side population (SP) cells were sorted with flow cytometry from FTC133 cells before and after EMT. The proportion of SP was compared and stemness, self-renewal and tumorigenicity in vitro were identified in SP cells.

Overexpression of HIF-1α induced FTC133 cells to undergo EMT. And it down-regulated epithelial marker E-cadherin, up-regulated mesenchymal marker vimentin and caused nucleus translocation of β-catenin and highly invasive and metastatic properties. Most importantly, the induction of EMT promoted proportion of stem-like side population cells (0.70% vs 0.03%, P < 0.05) with higher sphere formation and clone forming capability in contrast to non-side population cells.

EMT can induce cancer stem cell generation and tumor progression in thyroid cancers. Further understanding the role of EMT and cancer stem cells in cancer progression may reveal new preventive and therapeutic targets for thyroid cancers.