Ebinger Martin, Senf Leonore, Wachowski Olga, Scheurlen Wolfram
Department of Molecular Pathology, Institute of Pathology, Tübingen, Germany.
Pathol Oncol Res. 2004;10(1):17-21. doi: 10.1007/BF02893403. Epub 2004 Mar 18.
Methylation of promoter regions of CpG-rich sites is an important mechanism for silencing of tumor suppressor genes (TSG). To evaluate the role of tumor suppressor genes caspase-8 (CASP8), TIMP-3, E-cadherin (CDH1), p16INK4A, and MGMT in medulloblastoma tumorigenesis, 51 medulloblastomas (46 primary tumor specimens, 5 cell lines) were screened for methylation of promoter linked CpG-islands. For CASP8, we examined the 5' UTR region that has been shown to be associated with expression of CASP8. As detected by methylation specific PCR, methylation rate was low for TIMP-3 (3% of tumor samples; 1/5 cell lines), for MGMT (0% of tumor samples; 1/5 cell lines), for p16INK4A (2% of tumor samples; 2/5 cell lines) and for CDH1 (8% of tumor samples; 1/4 cell lines). CASP8, however, was methylated in 90% of tumor samples and 4/5 cell lines examined. Screening other tumor entities for CASP8 methylation, we found a similarly high level in 6 neuroblastoma cell lines in contrast to 5 osteosarcoma-, 4 Ewing's sarcoma- and 6 non-embryonic tumor cell lines without any increased promoter methylation. From our results we conclude that methylation of the CASP8 5' UTR region may play a role in inactivation of CASP8 in neural crest tumors.
富含CpG位点的启动子区域甲基化是肿瘤抑制基因（TSG）沉默的重要机制。为了评估肿瘤抑制基因半胱天冬酶8（CASP8）、金属蛋白酶组织抑制因子3（TIMP-3）、E-钙黏蛋白（CDH1）、p16INK4A和O6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）在髓母细胞瘤发生中的作用，对51例髓母细胞瘤（46例原发性肿瘤标本，5株细胞系）进行了启动子相关CpG岛甲基化筛查。对于CASP8，我们检测了已证明与CASP8表达相关的5'非翻译区（UTR）。通过甲基化特异性PCR检测，TIMP-3的甲基化率较低（3%的肿瘤样本；1/5细胞系），MGMT的甲基化率较低（0%的肿瘤样本；1/5细胞系），p16INK4A的甲基化率较低（2%的肿瘤样本；2/5细胞系），CDH1的甲基化率较低（8%的肿瘤样本；1/4细胞系）。然而CASP8，在所检测的90%的肿瘤样本和4/5细胞系中发生了甲基化。在其他肿瘤实体中筛查CASP8甲基化，我们发现在6株神经母细胞瘤细胞系中甲基化水平同样很高，相比之下，5株骨肉瘤、4株尤因肉瘤和6株非胚胎肿瘤细胞系中没有任何启动子甲基化增加。从我们的结果中我们得出结论，CASP8 5' UTR区域的甲基化可能在神经嵴肿瘤中CASP8的失活中起作用。
