CD44 exerts a functional role during EMT induction in cisplatinresistant head and neck cancer cells

A number of studies report that epithelial to mesenchymal transition (EMT) supports the generation and maintenance of cancer stem cells (CSCs), which show tumor seeding ability and drug resistance; however, the molecular mechanisms underlying induction of EMT-associated tumor malignancy remain unclear. The present study reports that oral cancer cells switch from expressing the CD44 variant form (CD44v) to expressing the standard form (CD44s) during acquisition of cisplatinresistance, which resulted in EMT induction. CD44s induced an EMT phenotype in cisplatin resistant cells by up-regulating ZEB1, a transcriptional repressor of E-cadherin. More importantly, CD44s up-regulated ZEB1 by suppressing microRNA- 200c, which is a non-coding RNA that directly represses the ZEB1 gene. These results demonstrate the importance of the association between platinum resistance and CD44s during EMT induction in oral cancer cells.