Abstract: ObjectiveTo separate,expansion,and explore the biological feature of CD44+ cells from the human nasopharyngeal carcinoma (NPC) SUNE-1 5-8F cell line. MethodsFlow cytometry was used to detect the expression of CD44 in SUNE-1 5-8F. Fluorescence-activated Cell Sorting was applied to purify CD44⁺ cells. MTT assay or clone formation assay was used to detect the differences of CD44+ and CD44^- cells in proliferation and differentiation ability. The expression of stem cell markers Oct4 and Bmi-1 was examined by reverse transcriptase polymerase chain reaction (RT-PCR). ResultsCD44 was positively expressed in about 52.5% of NPC SUNE-1 5-8F cell line. Regardless of serum-free medium and serum medium culture conditions,freshly sorted CD44+ cells showed stronger proliferative capacity than CD44^- and unsorted CD44⁺ cells. The expression levels of Bmi-1 and Oct4 mRNA in CD44⁺ cells were significantly higher than that in CD44^-cells. After 2Gy radiation,the average clone formation efficiency for CD44⁺ and CD44^-cells was(23.44±1.90)% and (7.78±1.17)%(P＜0.001),respectively. After Cisplatin and Docetaxel treatment,CD44⁺ cells showed a higher survival rate in the same drug concentration compared with CD44^-cells. ConclusionCD44+ cells have the biological characteristics of tumor stem cell and may be assumed as one of markers of NPC tumor stem cells.