肿瘤干细胞在腺样囊性癌细胞系增殖和分化中的作用

目的探讨腺样囊性癌细胞（adenoid cystic carcinoma cell，ACC）系中肿瘤干细胞的存在依据。方法采用单细胞体外培养法、免疫组化染色、免疫磁珠分离技术和动物实验等方法，分析常规培养的和经分离分群的不同细胞表型的ACC-2的体外增殖、分化特点和裸鼠体内成瘤能力的差异。结果体外培养至第8天，ACC-2单细胞仅有4．5％分裂、增殖，并非全部分裂。CD44^＋-CD24^-亚群占所有ACC-2细胞的8．1％，其中仅有25．71％的细胞长期存活和持续分裂。CD44^-和CD44^＋-CD24^＋细胞在体外培养条件下均无长期存活能力。不同表型的ACC-2体外单细胞培养实验发现，CD44^＋发生分裂的比例为8．4％，CD44^＋-CD24^-肿瘤细胞发生分裂的比例为14．7％，CD44^-和CD44^＋-CD24^＋细胞未发生分裂。裸鼠成瘤实验显示，CD44^＋-CD24^-的成瘤最低接种细胞数为1×10^3个／L，常规ACC-2最低成瘤细胞数为1×10^5个／L，CD44^-和CD44^＋-CD24^＋细胞则均无成瘤能力。免疫组化染色证实，CD44^＋-CD24^-肿瘤细胞具有分化成其他表型肿瘤细胞的能力。结论细胞表面抗原为CD44^＋-CD24^-的肿瘤细胞仅占ACC-2肿瘤细胞的极少部分，这些细胞具有极强的增殖能力和分化为其他表型肿瘤细胞的能力。ACC-2肿瘤细胞的增殖和成瘤能力源于CD44^＋-CD24^-ACC-2细胞亚群。ACC-2中存在肿瘤干细胞，而CD44^＋-CD24^-是ACC-2肿瘤干细胞必须兼备的表面标志。

Cancer stem cells: its existence, proliferation and differentiation in an adenoid cystic carcinoma cell line

OBJECTIVE: To investigate the evidences of the presence of tumor stem cells and its impact on the tumorigenesis of adenoid cystic carcinoma cell (ACC)-2 cell line by analyzing the biologic characteristics of different sub-clones of adenoid cystic carcinoma cell line. METHODS: In vitro individual cell culture was employed to observe the proliferating character of ACC-2 cells. The expression of CD44(+) and CD24(-) of ACC-2 cells were investigated by immunohistochemical. Immunomagnetic isolation of different phenotype of ACC-2 cells, followed by cell culture, was used to study the proliferating abilities of different clusters of the cell line. The hetero-transplanted tumor mold was established using BALB/C nude mice by subcutaneous injection of tumor cells. The tumorigenic and differentiating properties of the different cluster were investigated. RESULTS: Only 4.41% of cultured ACC-2 cell had ability of division, proliferation and establishment of cell clone. CD44(+)-CD24(-) cluster accounted for about 8.1% of total ACC-2 cells, among which, 25.71% cells could divide and proliferate. All of CD44 and CD44(+)-CD24(+) cells were failure to be eternal alive in the condition of in vitro individual cell culture. According to the results of in vivo tumorgenic study, the minimal cell quantity to develop a subcutaneous transplanted tumor by CD44(+)-CD24(-) cells was 1 x 10(3), where as the needed cell amount were 1 x 10(5) and 1 x 10(4) as to non-isolated ACC-2 cells and CD44(+) cells, respectively. The CD44(-) and CD44(+)-CD24(+) did not develope transplanted tumors. CD44(+)-CD24(-) ACC-2 cell could differentiate into cells of other phenotypes. CONCLUSIONS: CD44(+)-CD24(-) ACC-2 cells consist of a very small portion of all ACC-2 cells (about 4%). They have remarkable proliferating ability and can bear special phenotypes, The tumorogenic ability of CD44(+)-CD24(-) cells are stronger than that of CD44(+) and non-isolated ACC-2 cells. Eliminating of this cluster from ACC-2 would actually deprive the tumorogenic ability of the cell line.