Zhang Chenran, Meng Wei, Wang Jiajia, Lu Yicheng, Hu Guohan, Hu Liuhua, Ma Jie
Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, Shanghai, 200003, China.
Department of Pediatric Neurosurgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200092, China.
Cell Mol Neurobiol. 2017 Aug;37(6):1021-1027. doi: 10.1007/s10571-016-0435-3. Epub 2016 Oct 18.
Retinoblastoma protein-interacting zinc-finger gene 1 (RIZ1), a strong tumor suppressor, is silenced in many human cancers. Our previous studies showed that RIZ1 expression was negatively correlated with the grade of glioma and was a key predictor of patient survival. Therefore, RIZ1 could be a potential tumor suppressor during glioma pathogenesis, although the mechanism underlying RIZ1 gene inactivation in gliomas is unknown. We investigated the methylation status of the RIZ1 promoter in human glioma tissues and four glioblastoma (GBM) cell lines, and verified the effect of the methyltransferase inhibitor 5-aza-2-deoxycytidine (5-aza-CdR) on RIZ1 transcription and cell proliferation. Methylation-specific PCR (MSP) was performed to determine RIZ1 promoter methylation in human glioma specimens. The correlation between RIZ1 hypermethylation in tumors and clinicopathological features also was analyzed. 5-Aza-CdR treatment was used to reactivate gene expression silenced by hypermethylation in the U87 glioblastoma cell line, and real-time PCR was then used to measure RIZ1 expression. The ability of 5-aza-CdR to inhibit the proliferation of glioma cell lines whose RIZ1 promoters were hypermethylated was measured by bromodeoxyuridine (BrdU) incorporation. Among 51 human glioma specimens, RIZ1 promoter methylation was detected in 23 cases. Clinicopathological evaluation suggested that RIZ1 hypermethylation was negatively associated with tumor grade and patient age (P < 0.05). Hypermethylation of the RIZ1 promoter was detected in the U87 and U251 cell lines. RIZ1 mRNA expression in U87 cells was upregulated after treatment with 5-aza-Cdr, which correlated with inhibition of cell proliferation in a time- and concentration-dependent manner. Promoter hypermethylation may play an important role in the epigenetic silencing of RIZ1 expression in human glioma tissues and GBM cell lines.
视网膜母细胞瘤蛋白相互作用锌指基因1（RIZ1）是一种强大的肿瘤抑制因子，在许多人类癌症中均处于沉默状态。我们之前的研究表明，RIZ1的表达与胶质瘤的分级呈负相关，并且是患者生存的关键预测指标。因此，尽管RIZ1基因在胶质瘤中失活的机制尚不清楚，但RIZ1可能是胶质瘤发病过程中的一种潜在肿瘤抑制因子。我们研究了人类胶质瘤组织和四种胶质母细胞瘤（GBM）细胞系中RIZ1启动子的甲基化状态，并验证了甲基转移酶抑制剂5-氮杂-2'-脱氧胞苷（5-aza-CdR）对RIZ1转录和细胞增殖的影响。采用甲基化特异性PCR（MSP）检测人类胶质瘤标本中RIZ1启动子的甲基化情况。还分析了肿瘤中RIZ1高甲基化与临床病理特征之间的相关性。使用5-aza-CdR处理来重新激活U87胶质母细胞瘤细胞系中因高甲基化而沉默的基因表达，然后使用实时PCR检测RIZ1的表达。通过溴脱氧尿苷（BrdU）掺入法检测5-aza-CdR抑制RIZ1启动子高甲基化的胶质瘤细胞系增殖的能力。在51例人类胶质瘤标本中，有23例检测到RIZ1启动子甲基化。临床病理评估表明，RIZ1高甲基化与肿瘤分级和患者年龄呈负相关（P < 0.05）。在U87和U251细胞系中检测到RIZ1启动子高甲基化。用5-aza-Cdr处理后，U87细胞中RIZ1 mRNA表达上调，这与细胞增殖的抑制呈时间和浓度依赖性相关。启动子高甲基化可能在人类胶质瘤组织和GBM细胞系中RIZ1表达的表观遗传沉默中起重要作用。
