目的：研究中介体（mediator，Med）19对乳腺癌化疗敏感性的影响并分析其分子机制。方法： 选用多柔比星（adriamycin，ADM）耐药的人乳腺癌细胞MCF-7/ADM和亲本细胞MCF-7（NC组），采用慢病毒载体介导RNA干扰方法构建Med19稳定低表达的MCF-7/ADM与MCF-7细胞株（KD组），并用Real-time PCR和Western blotting方法验证干扰效果。CCK-8法检测慢病毒介导的 Med19敲减前后两种细胞对ADM、顺铂（cisplatin，DDP）和紫杉醇（taxinol，TAX）药物敏感性的变化。Real-time PCR和Western blotting检测Med19敲减对多药耐药基因1（multidrug resistance 1，MDR1）和细胞凋亡基因Bcl2、Bax及Caspase-3、active Caspase-3的表达的影响。流式细胞术检测敲减Med19及ADM处理对细胞凋亡的影响。结果： 与MCF-7相比， MCF-7/ADM细胞对ADM、DDP和TAX均具有耐药性。成功构建Med19稳定低表达的MCF-7/ADM与MCF-7细胞株，并且其对ADM、DDP、TAX的敏感性增加，药物作用IC50显著降低（均P<0.05）。MCF-7/ADM细胞Med19 mRNA和蛋白表达显著高于MCF-7细胞，Med19的敲减可降低MCF-7/ADM细胞中MDR1 mRNA与蛋白表达水平（均P<0.05）并可增加MCF-7/ADM及MCF-7细胞中凋亡相关active Caspase-3、Bax的蛋白表达，降低Bcl2的蛋白表达（均P<0.05）。此外，与NC及NC+ADM组相比，KD组及KD+ADM组凋亡水平显著增加（均P<0.05）。结论：Med19高表达参与乳腺癌化疗耐药，其机制可能与Med19调节MDR1的表达并影响细胞凋亡有关。

Objective:To explore the effect and molecular mechanism of mediator 19 (Med19) on drug sensitivity of breast cancer cells. Methods: Human breast cancer cell line MCF-7/ADM (adriamycin resistant) and it’s parental cell line MCF-7（NC groups） were selected. Lentivirus-mediated RNA-interference was used to construct MCF-7/ADM and MCF-7 cell lines that stably expressing low Med19 (KD groups), and the infection efficiency was detected by Real-time PCR and Western blotting assays. The change of drug-susceptibility to ADM, cisplatin (DDP) and taxinol (TAX) were examined with CCK-8 assay before and after Med19 knockdown. The effects of Med19 knockdown on the expressions of multidrug resistance gene 1(MDR1), Bcl2, Bax, Caspase-3 and active caspase-3 in breast cancer cells were detected by RT-PCR and Western Blotting assays, respectively. Effect of Med19 down-regulation and ADM treatment on apoptosis rates of MCF-7 and MCF-7/ADM cells were detected with flow cytometry assay. Results: Compared with MCF-7 cells, MCF-7/ADM cells exhibited drug resistance to ADM, DDP and TAX. MCF-7/ADM and MCF-7 cell lines that stably expressing low Med19level were successfully established; their drug-susceptibilities to ADM, DDP, TAX were increased, and the IC50 values of these three cytotoxic agents deceased obviously (all P<0.05). The mRNA and protein expressions of Med19 in MCF-7/ADM cells were significantly higher than those in MCF-7 cells, however, Med19 knockdown significantly inhibited the expressions of MDR1 mRNA and protein in MCF-7/ADM cells (all P<0.05); in addition, it significantly increased the expressions of active caspase-3 and Bax protein in both MCF-7/ADM and MCF-7 cells (all P<0.05) and decreased the expression of Bcl2 protein (all P<0.05). Besides, compared with NC or NC+ADM group, the apoptosis rate of the cells significantly increased in KD group or KD+ADM group (all P<0.05). Conclusions: High Med19 expression plays a particularly important role in chemoresistance of breast cancer, and the mechanism might correlate with Med19 regulating MDR1 expression and affecting apoptosis related genes.

国家自然科学基金面上项目资助（No. 81472485）；无锡市卫计委资助项目（No.Q201615, YGZXM14038No.YGZXQ1311）