State Key Laboratory of Oncology in South China, Department of Neurosurgery, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, China.
Cancer Chemother Pharmacol. 2013 Jul;72(1):147-58. doi: 10.1007/s00280-013-2180-3. Epub 2013 May 5.
Recent studies have reported that miR-181b contributes to chemoresistance in several cancer types and functions as a tumor suppressor in glioma. This study aimed to explore whether miR-181b could enhance the chemotherapeutic effect of temozolomide in glioma cells and sought to identify the candidate target genes which mediated the effect.
Using 48 frozen samples from patients with glioma who had received in vitro chemosensitivity assay, we measured MGMT promoter methylation status by methylation-specific PCR and miR-181b expression by qRT-PCR. Then, miR-181b expression level was correlated with temozolomide IC₅₀ and MGMT promoter methylation status. To investigate the mechanism of miR-181b-induced chemosensitivity, assays were performed using stable miR-181b-expressing transfectants of glioma cell lines created by a lentiviral system.
Glioma cells rich in miR-181b were more sensitive to temozolomide. miR-181b expression was not correlated with MGMT promoter methylation status. miR-181b combined with temozolomide enhanced glioma cell sensitivity and apoptosis. The effects were through posttranscriptional repression of MEK1. We demonstrated that miR-181b bound directly to the 3' untranslated regions of MEK1, thus reducing both the mRNA and protein levels of MEK1. Additionally, knockdown of MEK1 using small interfering RNA resulted in effects similar to ectopic miR-181b expression, whereas enforced expression of MEK1 lacking the 3' untranslated regions abrogated the effects. Finally, inverse correlation between miR-181b and MEK1 was established in glioma specimens.
miR-181b independently predicted chemoresponse to temozolomide and enhanced temozolomide sensitivity via MEK1 downregulation. A combination of miR-181b and temozolomide may be an effective therapeutic strategy for gliomas.
最近的研究表明，miR-181b 有助于几种癌症类型的化疗耐药，并在神经胶质瘤中作为肿瘤抑制因子发挥作用。本研究旨在探讨 miR-181b 是否可以增强神经胶质瘤细胞对替莫唑胺的化疗效果，并寻找介导该作用的候选靶基因。
使用来自接受体外药敏试验的胶质瘤患者的 48 个冷冻样本，通过甲基化特异性 PCR 测量 MGMT 启动子甲基化状态，并用 qRT-PCR 测量 miR-181b 的表达。然后，将 miR-181b 的表达水平与替莫唑胺 IC₅₀和 MGMT 启动子甲基化状态相关联。为了研究 miR-181b 诱导化疗敏感性的机制，使用通过慢病毒系统创建的神经胶质瘤细胞系的稳定 miR-181b 表达转染子进行了实验。
富含 miR-181b 的神经胶质瘤细胞对替莫唑胺更敏感。miR-181b 的表达与 MGMT 启动子甲基化状态无关。miR-181b 与替莫唑胺联合使用可增强神经胶质瘤细胞的敏感性和凋亡。这些作用是通过 MEK1 的转录后抑制实现的。我们证明 miR-181b 直接与 MEK1 的 3'非翻译区结合，从而降低 MEK1 的 mRNA 和蛋白水平。此外，使用小干扰 RNA 敲低 MEK1 导致与外源性 miR-181b 表达相似的效果，而缺乏 3'非翻译区的 MEK1 的强制表达则消除了这种效果。最后，在神经胶质瘤标本中建立了 miR-181b 与 MEK1 之间的负相关关系。
miR-181b 独立预测替莫唑胺的化疗反应，并通过下调 MEK1 增强替莫唑胺的敏感性。miR-181b 与替莫唑胺的联合使用可能是治疗神经胶质瘤的有效治疗策略。
