中文摘要：

目的 探讨低剂量辐射（LDR）对慢性髓细胞白血病干细胞（LSCs）中P16基因转录表达的影响及其临床意义.方法 取20例健康产妇脐血100 ml,免疫磁株法分离纯化CD34＋、CD38-的正常造血干细胞（HSCs）作为对照组;取20例初诊慢性髓细胞白血病（CML）慢性期患者骨髓液5-10 ml,免疫磁株法分离纯化CD34＋、CD38-、CD123＋的LSCs作为实验组.将HSCs及LSCs依据LDR剂量（0、12.5和50 cGy）辐照后收集细胞行RT-PCR和荧光实时定量PCR检测两种干细胞中p16基因的变化;另辐照后分别于24、48和72 h收集细胞,流式细胞仪检测两种干细胞的细胞周期和凋亡率.结果 CML-LSCs经12.5 cGy剂量照射后P16 mRNA表达略上调,50 cGy照射后明显增高（Z=-3.39,P〈0.01）,而HSCs经各剂量点LDR处理后p16基因转录水平无明显变化.CML-LSCs经12.5 cGy剂量处理后48 h出现G0/G1期阻滞,50 cGy剂量点照射后72 h出现了G0/G1期阻滞现象.CML-LSCs经LDR处理后,细胞的早期凋亡率随时间推移逐渐增加,50 cGy剂量照射后72 h处达到（17.75±11.76）%,与未照射组（6.13±4.71）%相比差异有统计学意义（Z=-2.37,P〈0.05）.结论 LDR可诱导CML-LSCs中P16基因转录水平的表达上调,使得CML-LSCs阻滞在G0/G1期,促进LSCs的凋亡,为P16基因作为CML中治疗的靶点及LDR在白血病中的应用提供理论依据.

英文摘要：

Objective To investigate the effect of low dose radiation on the expression of p16 gene in chronic myelogenous leukemia.Methods Leukemic stem cells（LSCs）which expressed CD34＋,CD38- and CD123＋ were isolated from bone marrow cells obtained from twenty patients newly-diagnosedas chronic myeloid leukemia with EasySep^TM magnet beads.Hematopoietie stem cells（HSCs） which expressed CD34＋ and CD38- were isolated from human cord blood cells obtained from twenty full-term deliveries with EasySep^TM magnet beads as control.HSCs vs LSCs samples were further divided into three dose groups,including 0,12.5 and 50 cGy,respectively.RT-PCR and real-time quantitative reverse transcription-polymerase chain reaction methods were used to detect mRNA expression of p16 gene in HSCs and LSCs after irradiation.Cells were harvested at different time for detection of cell cycle and apoptosis by flow cytometer.Results p16 mRNA level in CML-LSCs was increased slightly at 12.5 cGy,and significantly increased at 50 cGy（Z=-3.39,P〈0.01）,but ho significant change was found in HSCs.The percentage of CML-LSCs cell in G0/G1 stagewas increased 48 h after 12.5 cGy irradiation,and 72 h post-irradiation with 50 cGy.The apoptosis rate of CML-LSCs was gradually raised after LDR,especially at 72 h post-irradiation of 50 cGy[（17.75±11.76）%vs（6.13±4.71）%,Z=-2.37,P〈0.01 ].Conclusions p16 gene transcription could be up-regulated by low dose radiation,which might provide a theoretical evidence for CML therapy and LDR in leukemic clinical application.