中文摘要：

目的探讨高表达与低表达三磷酸腺苷（ATP）结合转运蛋白G超家族成员2（ABCG2）的人多药耐药鼻咽癌CNE2/DDP细胞（简写作ABCG2High细胞、ABCG2Low细胞）的生物学差异,分析两种细胞的耐药特点。方法分离ABCG2High和ABCG2Low细胞,检测其体外克隆形成率并分析细胞周期。流式细胞术（FCM）检测两种细胞传代前及传至第5代时ABCG2阳性表达率的差异。RT-PCR检测耐药基因ABCG2、Bcl-2、MDR1、MRP、MGMT的mRNA表达差异。MTT法检测两种细胞在1～14d的吸光度,绘制生长曲线;检测两种细胞对氟尿嘧啶、顺铂、长春新碱、卡铂、表阿霉素、柔红霉素、紫杉醇、丝裂霉素等化疗药物耐药性的差异。结果ABCG2High和ABCG2Low细胞在7d内的克隆形成率分别为25.24%±1.18%和16.28%±1.11%。FCM分析显示,ABCG2High的S期细胞占41.5%,ABCG2Low的G1/M0期细胞占63.9%。FCM分离后,ABCG2的表达率在ABCG2High细胞为98%,在ABCG2Low细胞为2%;两种细胞传至第5代,ABCG2在前者的表达率降低为75%,在后者升高至20%。RT-PCR显示,ABCG2mRNA在ABCG2High细胞中的表达明显高于ABCG2Low细胞,其他耐药基因在两种细胞中的表达无差异。生长曲线显示,ABCG2High细胞早期生长速度较ABCG2Low细胞快,后期生长速度逐渐减慢。耐药谱分析表明,ABCG2High细胞对8种抗肿瘤药物的IC50值高于ABCG2Low细胞两倍以上,两者差异有统计学意义（P〈0.05）。结论ABCG2High细胞是一种快周期细胞,而ABCG2Low细胞为慢周期细胞,前者更具有多药耐药的特点,可用于ABCG2介导的鼻咽癌细胞非经典多药耐药的研究。

英文摘要：

Objective To investigate the different biological characteristics of high-and low-expression of ATP-binding cassette transporter（ABCG2）in human multi-drug resistant nasopharyngeal carcinoma CNE2/DDP cell line（abbreviated as ABCG2High cell and ABCG2Low cell）,and to analyze drug-resistant characteristics of the two cell lines.Methods ABCG2High and ABCG2Low cells were isolated by flow cytometry,while their cloning efficiency,cell cycle distribution,and the expression of ABCG2 before and after the 5th passage were examined as well.mRNA expressions of drug-resistant genes,such as ABCG2,Bcl-2,MDR1,MRP and MGMT,were detected by reversed transcriptive polymerase chain reaction（RT-PCR）.MTT assay was utilized to detect the light absorbance（A）from day 1 to 14 to determine growth kinetics.Moreover,the drug sensitivity of the two cell lines to fluorouracil,cisplatin,vincristine,carboplatin,epirubicin,daunorubicin,paclitaxel and mitomycin were detected by MTT assay.Results The cloning efficiency of ABCG2High and ABCG2Low cells was 25.24%±1.18% and 16.28%±1.11%,respectively,on day 7.ABCG2High cells in S phase accounted for 41.5%,while the ABCG2Low cells in the G1/M0 phase went up to as high as 63.9%.The expression of ABCG2 in original ABCG2HighCNE2/DDP cells was 98%,while in ABCG2Low CNE2/DDP cells was 2%.However,at the 5th passage,the expression of ABCG2 decreased to 75% in the former cells and increased to 20% in the latter ones.The expression of ABCG2 mRNA in ABCG2High cells was obviously higher than that in ABCG2Low cells,while there was no difference in expression of other drug resistance genes between two cell lines.The growth velocity of ABCG2High cells exceeded that of ABCG2Low cells in early stage,but it slowed down 7 days later.MTT assay showed that IC50 of ABCG2High cells to 8 kinds of anti-tumor drugs were twofold higher than that of ABCG2Low cells,with statistically significant difference between them（P〈0.05）.Conclusions ABCG2High cell is a kind of fast cycle cell,on the contrary,ABCG2Low ce