Department of Biochemistry and Molecular Biology, Shandong University School of Medicine, Jinan 250012, China.
Cancer Lett. 2013 Aug 28;337(1):66-76. doi: 10.1016/j.canlet.2013.05.022. Epub 2013 May 18.
Retigeric acid B (RB) has been reported to exhibit its anti-tumor activity in vitro and in vivo. Here, we found that RB significantly inhibited activity of topoisomerase IIα (Topo IIα), leading to remarkable DNA damage in prostate cancer (PCa) cells as evidenced by a strong induction of γH2AX and DNA fragmentation. Activation of ATM and ATR sequentially led to induction of phospho-Chk1/2 and phospho-Cdc25 in response to RB. Blockade of ATM/ATR signaling resulted in the attenuation of RB-induced γH2AX, and partially rescued RB-mediated cell death. RB treatment also resulted in inactivation of DNA repair proteins such as phospho-BRCA1, impairment of HR, and NHEJ repair as indicated by DNA end-joining assays. Meanwhile, a stress-responsive gene activating transcription factor 3 (ATF3) was noted for its predominant expression in response to RB-induced DNA damage. Knockdown of ATF3 inhibited the RB-induced expression changes of cell cycle- and apoptosis-related genes such as DR5, DDIT4, CDC25A, GADD45A, and partially blocked RB-mediated inhibition on cell proliferation and induction of apoptosis, suggesting the crucial involvement of ATF3 in this event. Microarray data displayed that RB caused changes of genes required for damaged-DNA binding and repair, as well as ATF3 and its target genes. Our data firstly demonstrated that RB was a novel DNA Topo II inhibitor and triggered cell death by inducing DNA damage and stress-response, suggesting a promising anticancer agent.
Retigeric 酸 B（RB）已被报道在体外和体内显示其抗肿瘤活性。在这里，我们发现 RB 显著抑制拓扑异构酶 IIα（Topo IIα）的活性，导致前列腺癌（PCa）细胞中明显的 DNA 损伤，这可通过强烈诱导 γH2AX 和 DNA 片段化来证明。ATM 和 ATR 的激活依次导致磷酸化 Chk1/2 和磷酸化 Cdc25 的诱导，以响应 RB。阻断 ATM/ATR 信号导致 RB 诱导的 γH2AX 的减弱，并部分挽救了 RB 介导的细胞死亡。RB 处理还导致 DNA 修复蛋白如磷酸化 BRCA1 的失活、HR 的损害和 NHEJ 修复，如 DNA 末端连接测定所示。同时，应激反应基因激活转录因子 3（ATF3）因其对 RB 诱导的 DNA 损伤的主要表达而被注意到。ATF3 的敲低抑制了 RB 诱导的细胞周期和凋亡相关基因如 DR5、DDIT4、CDC25A、GADD45A 的表达变化，并部分阻断了 RB 对细胞增殖的抑制和诱导凋亡，表明 ATF3 在此事件中的关键作用。微阵列数据显示，RB 导致需要与损伤 DNA 结合和修复的基因以及 ATF3 和其靶基因的变化。我们的数据首次表明，RB 是一种新型的 DNA Topo II 抑制剂，通过诱导 DNA 损伤和应激反应引发细胞死亡，提示其作为一种有前途的抗癌药物。
