Objective To investigate the sensitization of PARP inhibitor through ionizing radiation ( IR) induced BRCA1 nuclear export, and the consequent defiency in DNA double strand break -repair function.Methods The loca-tion of BRCA1 in nuclear or/and cytoplasmic compartments was assessed by subcellular fractionation in MCF 7 cells after IR.The formation of γ-H2AX and Rad51 foci were detected by immunofluorescence staining .After labeled with Annexin V-FITC, apoptotic cells were analyzed by flow cytometry .In vivo anti-tumor activity was evaluated in MCF 7 xenograf-ted SCID mice.Results Nuclear BRCA1 of IR in treated cells were 41% that of mock irradiated cells .Cytoplasmic BRCA1 of IR in treated cells were 2.14 folds compare to that of mock irradiated cells .ABT-888 induced 7%and 30%Rad51 positive cell in IR treated or mock irradiated cells , respectively .Combined treatment of IR and ABT -888 induced 19%apoptosis cells, significantly higher than IR and ABT -888 alone.The combination of IR with ABT -888 in MCF7 xenograft model resulted in a superior therapeutic response compared to the single -agent alone .Conclusion Ionizing ra-diation can induced BRCA 1 nuclear export and sensitize PARP inhibitor .%目的 探讨放射线诱导的乳腺癌1号基因(BRCA1)出核效应对同源重组介导的DNA双链断裂损伤(DSB)修复功能的影响及对聚腺苷二磷酸核糖聚合酶(PARP)抑制剂的增敏作用.方法 采用亚细胞纯化及蛋白印迹法检测乳腺癌细胞株MCF7经放射线处理后BRCA1的亚细胞定位,同时采用免疫荧光法检测细胞核磷酸化的H2AX组蛋白(γ-H2AX)、Rad51核焦点形成.流式细胞技术检测细胞凋亡、克隆形成实验检测体外细胞存活情况,并制作裸鼠皮下移植瘤模型,分为4组,分别为:对照组、放射+DMSO组、假照+ABT-888(ABT-888为PARP抑制剂)组、放射+ABT-888组,每5 d为1个治疗周期,周期第1天给予2 Gy照射或假照射.第2~5天给予溶剂(对照组、放射+DMSO组)或20 mg/(kg·d)的ABT-888(假照+ABT-888组),总共给予4个周期的治疗.检测各组的体内抑瘤作用.结果 经4 Gy放射处理后,MCF7胞核BRCA1表达量减少,仅为对照组的41%,但胞浆内表达量明显增多,是对照组的2.14倍(P<0.01);同时MCF7细胞经4 Gy放射处理后ABT-888诱导的Rad51核焦点形成阳性细胞也较对照组明显减少(7%vs.30%,P=0.01).放射线和ABT-888联合应用导致MCF7细胞凋亡率增高(19%),与对照组(5%)、放射+DMSO组(9%)或假照+ABT-888组(6.2%)相比较差异有统计学意义(P<0.01).裸鼠移植瘤模型中放射+ABT-888组对肿瘤生长抑制作用明显优于假照+DM-SO组或假照+ABT-888组(P<0.01).结论 放射线可诱导BRCA1出核并增强PARP抑制剂的抗肿瘤作用.
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