Division of Neurosurgery, Arthur and Sonia Labatt Brain Tumor Research Centre, Hospital for Sick Children, Toronto, Ontario, Canada.
Neoplasia. 2010 Jan;12(1):20-7. doi: 10.1593/neo.91122.
Although medulloblastoma is the most common pediatric malignant brain tumor, its molecular underpinnings are largely unknown. We have identified rare, recurrent homozygous deletions of Kruppel-like Factor 4 (KLF4) in medulloblastoma using high-resolution single nucleotide polymorphism arrays, digital karyotyping, and genomic real-time polymerase chain reaction (PCR). Furthermore, we show that there is loss of physiological KLF4 expression in more than 40% of primary medulloblastomas both at the RNA and protein levels. Medulloblastoma cell lines drastically increase the expression of KLF4 in response to the demethylating agent 5-azacytidine and demonstrate dense methylation of the promoter CpG island by bisulfite sequencing. Methylation-specific PCR targeting the KLF4 promoter demonstrates CpG methylation in approximately 16% of primary medulloblastomas. Reexpression of KLF4 in the D283 medulloblastoma cell line results in significant growth suppression both in vitro and in vivo. We conclude that KLF4 is inactivated by either genetic or epigenetic mechanisms in a large subset of medulloblastomas and that it likely functions as a tumor suppressor gene in the pathogenesis of medulloblastoma.
虽然髓母细胞瘤是最常见的小儿脑恶性肿瘤，但它的分子基础在很大程度上是未知的。我们使用高分辨率单核苷酸多态性阵列、数字染色体组型分析和基因组实时聚合酶链反应（PCR），在髓母细胞瘤中鉴定出了罕见的、反复出现的 Kruppel 样因子 4（KLF4）纯合缺失。此外，我们还表明，在超过 40%的原发性髓母细胞瘤中，无论是在 RNA 还是蛋白质水平上，都存在生理 KLF4 表达的缺失。髓母细胞瘤细胞系对去甲基化剂 5-氮杂胞苷的反应急剧增加了 KLF4 的表达，并通过亚硫酸氢盐测序显示启动子 CpG 岛的密集甲基化。针对 KLF4 启动子的甲基化特异性 PCR 显示，大约 16%的原发性髓母细胞瘤存在 CpG 甲基化。KLF4 在 D283 髓母细胞瘤细胞系中的重新表达导致体外和体内的显著生长抑制。我们得出结论，KLF4 在很大一部分髓母细胞瘤中要么通过遗传机制要么通过表观遗传机制失活，并且它可能在髓母细胞瘤的发病机制中作为一种肿瘤抑制基因发挥作用。
