中文摘要：

目的：观察5’-氮杂-脱氧胞苷酸（5’-Aza-2’-deoxycytidine,5’-Aza-dC）联合他莫昔芬（tamoxifen,TAM）对乳腺癌耐药相关蛋白（breast cancer resistance protein,BCRP）介导的雌激素受体α（estrogen receptor alpha,ERα）阴性乳腺癌细胞多柔比星（adriamycin,ADR）耐药的影响。方法：5’-Aza-dC联合不同浓度TAM处理乳腺癌MDA-MB-435s细胞后,应用甲基化特异性PCR法检测ERα基因启动子区甲基化状态,蛋白质印迹法检测ERα与BCRP蛋白的表达,MTT法检测ADR半数抑制浓度（half inhibitory concentration,IC50）。结果：5’-Aza-dC可浓度依赖性去除MDA-MB-435s细胞ERα基因启动子区甲基化并恢复ERα蛋白的表达,0.5μmol/L5’-Aza-dC可获得较高水平ERα蛋白的表达;0.5μmol/L5’-Aza-dC或100μmol/LTAM单独处理细胞,对BCRP蛋白的表达水平无明显影响;0.5μmol/L5’-Aza-dC联合1、10和100μmol/LTAM处理细胞后,BCRP蛋白的相对表达量分别降低了18.3%、41.1%和75.3%;0.5μmol/L5’-Aza-dC联合10和100μmol/LTAM处理后,细胞对ADR敏感度分别增强至阴性对照组的1.4和4.2倍。结论：在5’-Aza-dC恢复ERα表达的前提下,TAM可显著下调ERα阴性乳腺癌细胞BCRP蛋白的表达并增强细胞对ADR的敏感度,2者联合可能成为逆转ERα阴性乳腺癌细胞多药耐药的一种途径。

英文摘要：

Objective：To observe the effect of tamoxifen（TAM） in combination with 5＇-Aza-2＇-deoxycytidine（5＇-Aza-dC） on the resistance to adriamycin（ADR） in estrogen receptor-alpha（ERα）-negative breast cancer cells induced by breast cancer resistance protein（BCRP）.Methods：MDA-MB-435s breast cancer cells were treated with 5＇-Aza-dC plus TAM at different concentrations.The methylation of ERα gene promoter region was examined by methylation-specific PCR.The expressions of ERα and BCRP proteins were detected by Western blotting.The half inhibitory concentration（IC50） value was determined by MTT assay.Results：The 5＇-Aza-dC induced demethylation of ERα gene promoter region and restored the expression of ERα protein in a concentration-dependent manner.A higher expression level of ERα protein induced by 0.5 μmol/L 5＇-Aza-dC was observed.There was no change in the expression level of BCRP after treatment with 0.5 μmol/L 5＇-Aza-dC or 100 μmol/L TAM alone.The expression levels of BCRP were decreased 18.3%,41.1% and 75.3% after treatment with 0.5 μmol/L 5＇-Aza-dC plus 1,10 and 100 μmol/L TAM,respectively.The cellular sensitivity to ADR after treatment with 0.5 μmol/L 5＇-Aza-dC plus 10 or 100 μmol/L TAM was 1.4-or 4.2-fold as high as that in the untreated group.Conclusion：If the expression level of ERα protein is restored by 5＇-Aza-dC,TAM can significantly down-regulate the expression level of BCRP and promote the cellular sensitivity to ADR in ERα-negative breast cancer cells.Combination of TAM and 5＇-Aza-dC may be used as a new approach for reversing multidrug resistance in ERα-negative breast cancer cells.