Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, Vanderbilt University School of Medicine, B1100 Medical Center North, Nashville, TN 37232, USA.
Cancer Res. 2013 Aug 1;73(15):4758-69. doi: 10.1158/0008-5472.CAN-12-4560. Epub 2013 May 29.
In metastatic ovarian cancer, resistance to platinum chemotherapy is common. Although the orphan nuclear receptor TR3 (nur77/NR4A1) is implicated in mediating chemotherapy-induced apoptosis in cancer cells, its role in ovarian cancer has not been determined. In an ovarian cancer tissue microarray, TR3 protein expression was elevated in stage I tumors, but downregulated in a significant subset of metastatic tumors. Moreover, TR3 expression was significantly lower in platinum-resistant tumors in patients with metastatic disease, and low TR3 staining was associated with poorer overall and progression-free survival. We have identified a direct role for TR3 in cisplatin-induced apoptosis in ovarian cancer cells. Nucleus-to-cytoplasm translocation of TR3 was observed in cisplatin-sensitive (OVCAR8, OVCAR3, and A2780PAR) but not cisplatin-resistant (NCI/ADR-RES and A2780CP20) ovarian cancer cells. Immunofluorescent analyses showed clear overlap between TR3 and mitochondrial Hsp60 in cisplatin-treated cells, which was associated with cytochrome c release. Ovarian cancer cells with stable shRNA- or transient siRNA-mediated TR3 downregulation displayed substantial reduction in cisplatin effects on apoptotic markers and cell growth in vitro and in vivo. Mechanistic studies showed that the cisplatin-induced cytoplasmic TR3 translocation required for apoptosis induction was regulated by JNK activation and inhibition of Akt. Finally, cisplatin resistance was partially overcome by ectopic TR3 overexpression and by treatment with the JNK activator anisomycin and Akt pathway inhibitor, wortmannin. Our results suggest that disruption of TR3 activity, via downregulation or nuclear sequestration, likely contributes to platinum resistance in ovarian cancer. Moreover, we have described a treatment strategy aimed at overcoming platinum resistance by targeting TR3.
在转移性卵巢癌中，对铂类化疗的耐药性很常见。尽管孤儿核受体 TR3（nur77/NR4A1）被认为在介导癌细胞化疗诱导的细胞凋亡中起作用，但它在卵巢癌中的作用尚未确定。在卵巢癌组织微阵列中，TR3 蛋白表达在 I 期肿瘤中升高，但在大量转移性肿瘤中下调。此外，在患有转移性疾病的患者中，铂类耐药肿瘤中的 TR3 表达明显降低，低 TR3 染色与总体和无进展生存期较差相关。我们已经确定了 TR3 在卵巢癌细胞中顺铂诱导凋亡中的直接作用。在顺铂敏感的（OVCAR8、OVCAR3 和 A2780PAR）但不是顺铂耐药的（NCI/ADR-RES 和 A2780CP20）卵巢癌细胞中观察到 TR3 的核质易位。免疫荧光分析显示，在顺铂处理的细胞中，TR3 与线粒体 Hsp60 之间存在明显的重叠，这与细胞色素 c 释放有关。稳定的 shRNA 或瞬时 siRNA 介导的 TR3 下调的卵巢癌细胞在体外和体内对顺铂对凋亡标志物和细胞生长的影响明显减少。机制研究表明，顺铂诱导的细胞质 TR3 易位对于凋亡诱导是通过 JNK 激活和 Akt 抑制来调节的。最后，通过异位 TR3 过表达以及使用 JNK 激活剂anisomycin 和 Akt 通路抑制剂wortmannin，部分克服了顺铂耐药性。我们的结果表明，通过下调或核隔离破坏 TR3 活性可能导致卵巢癌中的铂类耐药。此外，我们描述了一种通过靶向 TR3 来克服铂类耐药性的治疗策略。
