Caspase-8 gene expression in neuroblastoma
Caspase-8 gene expression in neuroblastoma
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DOI：
10.1196/annals.1322.017
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发表时间：
2004-01-01
期刊：
影响因子：
--
通讯作者：
Romani, M
中科院分区：
文献类型：
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作者：
Casciano, I;Banelli, B;Romani, M
神经母细胞瘤（NB）是一种婴儿期的实体瘤，具有很高的自发消退率，这种现象可能反映了凋亡/分化程序的激活。事实上，参与细胞凋亡调节的分子（如p73或生存素）的表达水平是NB患者的预后因素。caspase-8基因（CASP 8）编码凋亡级联反应顶端的关键酶。尽管据报道CASP 8基因的一个假定调控区的甲基化抑制了其在一些MYCN扩增的NB中的转录，但我们的研究结果表明，caspase-8的转录失活发生在一个独立于MYCN扩增或CpG甲基化的原发性NB亚组中。此外，凋亡剂芬维A胺（4 HPR）和干扰素-γ（IFN-γ）诱导caspase-8表达，而不改变该基因的甲基化状态。然而，与未扩增的样品相比，MYCN扩增的肿瘤中CASP 8基因内和启动子区域的甲基化水平更高。这种现象可能反映了MYCN扩增和MYCN单拷贝肿瘤中存在不同的DNA甲基化错误。为了获得关于调节这一关键凋亡基因表达的机制的信息，我们搜索了潜在的CASP 8调节区，并在该基因的5 '末端克隆了一个DNA元件，该元件仅在表达caspase-8的NB细胞系中功能性地充当启动子。视黄酸类似物4 HPR、IFN-γ和去甲基化剂5-氮杂胞苷在缺乏内源性半胱天冬酶-8的NB细胞中激活该启动子，表明该元件可以调节组成型和诱导型CASP 8表达。这些结果还表明，细胞基因组的去甲基化可能通过反式作用因子的作用上调CASP 8。我们的研究结果为CASP 8的调控提供了新的见解，CASP 8是一种在各种生理和病理条件下发挥重要作用的基因。
Neuroblastoma (NB) is a solid tumor of infancy that presents a high rate of spontaneous regression, a phenomenon that likely reflects the activation of an apoptotic/differentiation program. Indeed, the level of expression of molecules involved in the regulation of apoptosis, such as p73 or survivin, is a prognostic factor in NB patients. The caspase-8 gene (CASP8) encodes a key enzyme at the top of the apoptotic cascade. Although methylation of a putative regulatory region of the CASP8 gene reportedly inhibits its transcription in some MYCN-amplified NB, our results indicate that the transcriptional inactivation of caspase-8 occurs in a subset of primary NB independently of MYCN amplification or CpG methylation. In addition, the apoptotic agent fenretinide (4HPR) and interferon-gamma (IFN-gamma) induce caspase-8 expression without modifying the methylation status of this gene. Nevertheless, the methylation level of CASP8 intragenic and promoter regions is higher in MYCN-amplified tumors as compared to nonamplified samples. This phenomenon might reflect the existence of distinct DNA methylation errors in MYCN-amplified and MYCN-single copy tumors. To gain information on the mechanisms that regulate the expression of this crucial apoptotic gene, we searched for potential CASP8 regulatory regions and cloned a DNA element at the 5 ' terminus of this gene that functionally acts as a promoter only in NB cell lines that express caspase-8. The retinoic acid analogue 4HPR, IFN-gamma, and the demethylating agent 5-aza-cytidine activate this promoter in NB cells that lack endogenous caspase-8, indicating that this element may regulate both constitutive and inducible CASP8 expression. These results indicate also that demethylation of the cellular genome may upregulate CASP8 through the action of trans-acting factors. Our results provide new insights to the regulation of CASP8, a gene with an essential role in a variety of physiologic and pathologic conditions.