목적: To evaluate the impact of cancer stem cells (CSC) on insensitivity to radiotherapy in head and neck squamous cell carcinoma (HNSCC) using in vitro and in vivo model. 방법:A radioresistant cell line, FaDu-R, was established by fractionated ionizing radiation. Cells with high and low CD44/ALDH activity (CD44high/ALDHhigh and CD44low/ALDHlow) were isolated. In vitro motility was assessed using a wound healing assay and matrigel invasion assay. CD44high/ALDHhigh and CD44low/ALDHlow populations were implanted into NOD/SCID mice and monitored for tumor development. 결과:FaDu-R cells demonstrated significantly increased cell viability compared with parental cells after radiation exposure. CD44high/ALDHhigh FaDu-R cells demonstrated significantly faster wound closure (p<0.05) and more efficient invasion (p<0.05) compared to the CD44high/ALDHhigh FaDu cells or CD44low/ALDHlow FaDu-R cells. There was a significant difference in tumor volume between CD44high/ALDHhigh FaDu-R cells and CD44high/ALDHhigh FaDu cells (p<0.05) and CD44low/ALDHlow FaDu-R cells (p<0.05). 결론:The CSC was related to invasion and tumorigenesis in radioresistant HNSCC cell line. This concept might help to improve understanding of mechanism and to develop drugs to overcome radioresistance during radiotherapy.