Oncogenomics and Cancer Proteomics Laboratory; Genomics Sciences Program; Autonomous University of Mexico City; Mexico DF, Mexico.
Virus and Cancer Laboratory; National Institute of Cancerology; Mexico DF, Mexico.
Cancer Biol Ther. 2014 Jun 1;15(6):777-88. doi: 10.4161/cbt.28551. Epub 2014 Mar 18.
In tumor cells the effectiveness of anti-neoplastic agents that cause cell death by induction of DNA damage is influenced by DNA repair activity. RAD50 protein plays key roles in DNA double strand breaks repair (DSBs), which is crucial to safeguard genome integrity and sustain tumor suppression. However, its role as a potential therapeutic target has not been addressed in breast cancer. Our aim in the present study was to analyze the expression of RAD50 protein in breast tumors, and evaluate the effects of RAD50-targeted inhibition on the cytotoxicity exerted by cisplatin and anthracycline and taxane-based therapies in breast cancer cells. Immunohistochemistry assays on tissue microarrays indicate that the strong staining intensity of RAD50 was reduced in 14% of breast carcinomas in comparison with normal tissues. Remarkably, RAD50 silencing by RNA interference significantly enhanced the cytotoxicity of cisplatin. Combinations of cisplatin with doxorubicin and paclitaxel drugs induced synergistic effects in early cell death of RAD50-deficient MCF-7, SKBR3, and T47D breast cancer cells. Furthermore, we found an increase in the number of DSBs, and delayed phosphorylation of histone H2AX after cisplatin treatment in RAD50-silenced cells. These cellular events were associated to a dramatical increase in the frequency of chromosomal aberrations and a decrease of cell number in metaphase. In conclusion, our data showed that RAD50 abrogation impairs DNA damage response and sensitizes breast cancer cells to cisplatin-combined therapies. We propose that the development and use of inhibitors to manipulate RAD50 levels might represent a promising strategy to sensitize breast cancer cells to DNA damaging agents.
在肿瘤细胞中，通过诱导 DNA 损伤导致细胞死亡的抗肿瘤药物的有效性受到 DNA 修复活性的影响。RAD50 蛋白在 DNA 双链断裂修复 (DSBs) 中发挥关键作用，这对于保护基因组完整性和维持肿瘤抑制至关重要。然而，其作为潜在治疗靶点的作用在乳腺癌中尚未得到解决。本研究旨在分析 RAD50 蛋白在乳腺癌肿瘤中的表达，并评估 RAD50 靶向抑制对顺铂和蒽环类药物及紫杉烷类药物治疗在乳腺癌细胞中细胞毒性的影响。组织微阵列的免疫组织化学检测表明，与正常组织相比，14%的乳腺癌中 RAD50 的强染色强度降低。值得注意的是，RAD50 的 RNA 干扰沉默显著增强了顺铂的细胞毒性。顺铂与阿霉素和紫杉醇药物的组合在 RAD50 缺陷型 MCF-7、SKBR3 和 T47D 乳腺癌细胞的早期细胞死亡中诱导协同作用。此外，我们发现 RAD50 沉默细胞中 DSB 数量增加，顺铂处理后组蛋白 H2AX 的磷酸化延迟。这些细胞事件与染色体畸变频率的急剧增加和中期细胞数量的减少有关。总之，我们的数据表明，RAD50 缺失破坏了 DNA 损伤反应，并使乳腺癌细胞对顺铂联合治疗敏感。我们提出，开发和使用抑制剂来操纵 RAD50 水平可能是使乳腺癌细胞对 DNA 损伤剂敏感的一种有前途的策略。
