Intracellular clusterin negatively regulates ovarian chemoresistance: compromised expression sensitizes ovarian cancer cells to paclitaxel
Intracellular clusterin negatively regulates ovarian chemoresistance: compromised expression sensitizes ovarian cancer cells to paclitaxel
复制标题
DOI：
10.1007/s13277-011-0207-0
复制
发表时间：
2011-10-01
期刊：
影响因子：
--
通讯作者：
Sakuragi, Noriaki
中科院分区：
文献类型：
--
作者：
Hassan, Mohamed Kamel;Watari, Hidemichi;Sakuragi, Noriaki
了解导致紫杉醇 (TX) 耐药的分子事件对于确定预防化疗耐药的有效方法是必要的。此前，我们实验室的结果表明，分泌型簇蛋白 (CLU) 形式可积极介导卵巢癌细胞中的 TX 反应。因此，我们有兴趣研究另一种非分泌形式（细胞内簇蛋白（i-CLU））在化疗反应中的作用。在这里，我们提供的证据表明，i-CLU 形式主要定位于细胞核，并在 TX 反应性 KF 细胞中与 TX 抗性细胞、KF-TX 细胞和卵巢癌细胞中差异表达，并负调节细胞化疗反应。通过从全长 CLU cDNA 中删除分泌引导信号肽来克隆 I-CLU，并在 OVK-18 细胞中瞬时过表达。截短的i-CLU的强制表达主要在细胞核中检测到，并显着减少细胞生长，使细胞积累在G1期，最终通过凋亡而死亡。重要的是，诱导型启动子下 i-CLU 的表达受损是可以耐受的，不会诱导细胞凋亡，但会使卵巢癌细胞对 TX 敏感。然后我们证明这种敏化机制与细胞周期无关，并且依赖于 i-CLU/Ku70 结合，可能是由于控制了细胞核中可用于 DNA 修复的 Ku70 的游离量。卵巢肿瘤组织中的 CLU 免疫组织化学结果证实了复发肿瘤中核 CLU 染色的延迟，尽管其原发肿瘤组织显示核 CLU 染色。因此，关于 CLU 在化疗反应/耐药中功能的争议数据可能可以通过当肿瘤获得化疗耐药时 CLU 表达模式和细胞内定位的变化来解释。
Understanding the molecular events that lead to paclitaxel (TX) resistance is necessary to identify effective means to prevent chemoresistance. Previously, results from our lab revealed that secretory clusterin (CLU) form positively mediates TX response in ovarian cancer cells. Thus, we had interest to study the role of another non-secreted form (intracellular clusterin (i-CLU)) in chemo-response. Here, we provide evidences that i-CLU form localizes mainly in the nucleus and differentially expressed in the TX-responsive KF cells, versus TX-resistant, KF-TX, ovarian cancer cells and negatively regulate cellular chemo-response. I-CLU was cloned, by deleting the secretion-leading signaling peptide from full-length CLU cDNA, and transiently over-expressed in OVK-18 cells. Forced expression of truncated i-CLU was mainly detectable in the nuclei and significantly reduced cellular growth, accumulating cells in G1 phase which finally died through apoptosis. Importantly, compromised expression of i-CLU under an inducible promoter was tolerated and did not induce apoptosis but sensitized ovarian cancer cells to TX. We then demonstrated that this sensitization mechanism was cell cycle independent and relied on i-CLU/Ku70 binding probably due to controlling the free amount of Ku70 available for DNA repair in the nucleus. Results from CLU immunehistochemistry in ovarian tumor tissues verified the retardation of nuclear CLU staining in the recurrent tumor even though their primary counterparts showed nuclear CLU staining. Thus, the controversial data on CLU function in chemo-response/resistance may be explained by a shift in the pattern of CLU expression and intracellular localization as well when tumor acquires chemoresistance.