Wu Hao, Schiff Devora S, Lin Yong, Neboori Hanmanth J R, Goyal Sharad, Feng Zhaohui, Haffty Bruce G
a Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey.
Radiat Res. 2014 Dec;182(6):618-25. doi: 10.1667/RR13856.1.
Breast-conserving surgery followed by radiation therapy has become the standard of care for early stage breast cancer. However, there are some patients that develop a local failure. We have previously shown that Bcl-2 overexpression was associated with an increased risk of local recurrence in patients with early stage breast cancer. The purpose of this study was to explore an approach to overcome radiation resistance by targeting pro-survival Bcl-2 family proteins in breast cancer cells. The breast cancer cell lines MCF-7, ZR-75-1 and MDA-MB231 were used in this study. siRNAs were employed to silence myeloid cell leukemia 1 (Mcl-1). A small molecule inhibitor of Bcl-2, ABT-737, was used to target anti-apoptotic Bcl-2 family proteins. Apoptosis was identified by FITC Annexin V, PI staining and Western blot analysis. The sensitivity to ionizing radiation and ABT-737 were measured by clonogenic assays. The effect of radiation and ABT-737 was also tested in a MCF-7 xenograft mouse model. Our data demonstrate that the combination of ABT-737 and radiation-induced apoptosis had an inhibitory effect on breast cancer cell proliferation. However, treatment with ABT-737 resulted in elevated Mcl-1 in breast cancer cell lines. Targeting Mcl-1 by siRNA sensitized MCF-7 cells to ABT-737. We revealed that radiation blunted Mcl-1 elevation induced by ABT-737, and that radiation downregulated Mcl-1 by promoting its degradation. Our results indicate that radiation and ABT-737 exert a synergistic effect on breast cancer cell lines through downregulating Mcl-1 and activating the bak-apoptotic pathway. These results support the combination of radiation and pro-survival Bcl-2 family inhibitor as a potential novel therapeutic strategy in the local-regional management of breast cancer.
保乳手术联合放射治疗已成为早期乳腺癌的标准治疗方案。然而，仍有一些患者会出现局部复发。我们之前的研究表明，Bcl-2过表达与早期乳腺癌患者局部复发风险增加有关。本研究的目的是探索一种通过靶向乳腺癌细胞中促生存的Bcl-2家族蛋白来克服放射抗性的方法。本研究使用了乳腺癌细胞系MCF-7、ZR-75-1和MDA-MB231。采用小干扰RNA（siRNAs）沉默髓样细胞白血病1（Mcl-1）。使用Bcl-2小分子抑制剂ABT-737靶向抗凋亡Bcl-2家族蛋白。通过FITC Annexin V、PI染色和蛋白质免疫印迹分析鉴定细胞凋亡。通过克隆形成试验测定对电离辐射和ABT-737的敏感性。还在MCF-7异种移植小鼠模型中测试了辐射和ABT-737的效果。我们的数据表明，ABT-737与辐射诱导的细胞凋亡联合对乳腺癌细胞增殖具有抑制作用。然而，用ABT-737处理导致乳腺癌细胞系中Mcl-1升高。通过siRNA靶向Mcl-1可使MCF-7细胞对ABT-737敏感。我们发现，辐射可减弱ABT-737诱导的Mcl-1升高，并且辐射通过促进Mcl-1降解而下调其表达。我们的结果表明，辐射和ABT-737通过下调Mcl-1并激活bak凋亡途径对乳腺癌细胞系发挥协同作用。这些结果支持将放射治疗与促生存Bcl-2家族抑制剂联合作为乳腺癌局部区域治疗的一种潜在新治疗策略。
