Key Laboratory of Malignant Tumor Gene Regulation and Target Therapy of Guangdong Higher Education Institutes, Research Center of Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
Oncogene. 2013 Feb 28;32(9):1155-63. doi: 10.1038/onc.2012.132. Epub 2012 May 14.
Chromosome 1p36.23 is frequently deleted in glioblastoma multiforme (GBM). miR-34a localizes in this region. Our experiments found that miR-34a was often deleted and epidermal growth factor receptor (EGFR) was frequently amplified in genomic DNA of 55 GBMs using single-nucleotide polymorphism DNA microarray. Notably, we found that the mean survival time was significantly shortened for patients whose GBMs had both EGFR amplification and miR-34a deletion. Expression of miR-34a was significantly lower in GBM samples compared with normal brain tissue. Forced expression of miR-34a in GBM cells decreased their ability to migrate and profoundly decreased their levels of cyclin-A1, -B1, -D1, and -D3, as well as cyclin-dependent kinase and increased expression of cyclin kinase inhibitor proteins (p21, p27). Also, human GBM cells (U251) stable overexpressing mir-34a formed smaller tumors when growing as xenografts in immunodeficient mice compared with wild-type U251 GBM cells. Furthermore, the protein expression of EGFR decreased in the cells with forced overexpression of miR-34a. Additional studies showed that mir-34a targeted Yin Yang-1 (YY1) and YY1 is a transcription factor that can stimulate the expression of EGFR. Thus, our data suggest that miR-34a acts as a tumor suppressor by inhibiting growth of GBM cells in vitro and in vivo associated with moderating the expression of cell-cycle proteins and EGFR. Moreover, we discovered for the first time that both deletion of miR-34a and amplification of EGFR were associated with significantly decreased overall survival of GBM patients.
1p36.23 号染色体在多形性胶质母细胞瘤（GBM）中经常缺失。miR-34a 定位于该区域。我们的实验发现，使用单核苷酸多态性 DNA 微阵列在 55 例 GBM 的基因组 DNA 中，miR-34a 经常缺失，表皮生长因子受体（EGFR）经常扩增。值得注意的是，我们发现，GBM 中既有 EGFR 扩增又有 miR-34a 缺失的患者的平均生存时间明显缩短。与正常脑组织相比，GBM 样本中 miR-34a 的表达明显降低。在 GBM 细胞中强制表达 miR-34a 降低了它们的迁移能力，并显著降低了细胞周期蛋白 A1、B1、D1 和 D3、细胞周期蛋白依赖性激酶的水平，并增加了细胞周期蛋白激酶抑制剂蛋白（p21、p27）的表达。此外，与野生型 U251 GBM 细胞相比，在免疫缺陷小鼠中作为异种移植物生长时，稳定过表达 mir-34a 的人 GBM 细胞（U251）形成的肿瘤较小。此外，在强制过表达 miR-34a 的细胞中，EGFR 的蛋白表达降低。进一步的研究表明，miR-34a 靶向 Yin Yang-1（YY1），而 YY1 是一种可以刺激 EGFR 表达的转录因子。因此，我们的数据表明，miR-34a 通过抑制体外和体内 GBM 细胞的生长来发挥肿瘤抑制作用，与调节细胞周期蛋白和 EGFR 的表达有关。此外，我们首次发现 miR-34a 的缺失和 EGFR 的扩增均与 GBM 患者的总生存期明显缩短有关。
