The differentiated epithelial cells could be transformed into mesenchymal cells through a cellular program named epithelial—mesenchymal transformation（EMT）, which plays an important role in development, carcinoma invasion and also chemoresistance. Since chemoresistance always cause the failure of chemotherapy, to overcome chemoresistance is key to maintain the effectiveness of chemotherapy. This article reviews EMT and its biological significance, its association with chemoresistace, especially in head and neck cancer.
