Department of Neurosurgery, Sir Run Run Shaw Hospital, College of Medical Sciences, Zhejiang University, Hangzhou, China.
Biochem Biophys Res Commun. 2013 Aug 9;437(4):565-72. doi: 10.1016/j.bbrc.2013.06.116. Epub 2013 Jul 9.
In the current study, we aimed to understand the potential role of leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) in TMZ-resistance of U251 glioma cells. We established TMZ-resistant U251 clones (U251/TMZ cells), which expressed low level of LRIG1, but high levels of epidermal growth factor receptor (EGFR), topoisomerase-2 (Topo-2) and Bcl-2. Depletion of LRIG1 by the targeted RNA interference (RNAi) upregulated EGFR/Topo-2/Bcl-2 in U251 cells, and the cells were resistant to TMZ. Reversely, over-expression of LRIG1 in U251 cells downregulated EGFR/Topo-2/Bcl-2 expressions, and cells were hyper-sensitive to TMZ. Our data suggested EGFR-dependent mammalian target of rapamycin (mTOR) activation was important for Topo-2 and Bcl-2 expressions in U251/TMZ cells. The EGFR inhibitor and the mTOR inhibitor downregulated Topo-2/Bcl-2 expressions, both inhibitors also restored TMZ sensitivity in U251/TMZ cells. Finally, inhibition of Topo-2 or Bcl-2 by targeted RNAi(s) knockdown or by the corresponding inhibitor re-sensitized U251/TMZ cells to TMZ, indicating that both Topo-2 and Bcl-2 were important for TMZ resistance in the resistant U251 cells. Based on these results, we concluded that LRIG1 inhibits EGFR expression and the downstream signaling activation, interferes with Bcl-2/Topo-2 expressions and eventually sensitizes glioma cells to TMZ.
在本研究中，我们旨在探讨富含亮氨酸重复序列和免疫球蛋白样结构域 1（LRIG1）在替莫唑胺（TMZ）耐药的 U251 神经胶质瘤细胞中的潜在作用。我们建立了 TMZ 耐药的 U251 克隆（U251/TMZ 细胞），这些细胞表达低水平的 LRIG1，但高水平的表皮生长因子受体（EGFR）、拓扑异构酶-2（Topo-2）和 Bcl-2。靶向 RNA 干扰（RNAi）下调 LRIG1 表达可上调 U251 细胞中的 EGFR/Topo-2/Bcl-2，使细胞对 TMZ 耐药。相反，在 U251 细胞中过表达 LRIG1 可下调 EGFR/Topo-2/Bcl-2 的表达，使细胞对 TMZ 高度敏感。我们的数据表明，EGFR 依赖性哺乳动物雷帕霉素靶蛋白（mTOR）的激活对于 U251/TMZ 细胞中 Topo-2 和 Bcl-2 的表达很重要。EGFR 抑制剂和 mTOR 抑制剂下调了 Topo-2/Bcl-2 的表达，两种抑制剂也恢复了 U251/TMZ 细胞对 TMZ 的敏感性。最后，通过靶向 RNAi(s)敲低或相应抑制剂下调 Topo-2 或 Bcl-2，使 U251/TMZ 细胞对 TMZ 重新敏感，表明 Topo-2 和 Bcl-2 对耐药 U251 细胞的 TMZ 耐药均很重要。基于这些结果，我们得出结论，LRIG1 抑制 EGFR 表达及其下游信号激活，干扰 Bcl-2/Topo-2 的表达，最终使神经胶质瘤细胞对 TMZ 敏感。
