Grotzer M A, Eggert A, Zuzak T J, Janss A J, Marwaha S, Wiewrodt B R, Ikegaki N, Brodeur G M, Phillips P C
Division of Oncology, The Children's Hospital of Philadelphia, Pennsylvania 19104, USA.
Oncogene. 2000 Sep 21;19(40):4604-10. doi: 10.1038/sj.onc.1203816.
TNF-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in adult malignant glioma and various other human solid tumor models but not in normal tissues. To characterize the TRAIL death pathway in childhood primitive neuroectodermal brain tumor (PNET), 8 human PNET cell lines were tested for TRAIL-induced apoptosis. TRAIL-sensitivity of the PNET cell lines was correlated with mRNA expression levels of TRAIL, its agonistic (TRAIL-R1, TRAIL-R2) and antagonistic (TRAIL-R3, TRAIL-R4) receptors, cellular FLICE-like inhibitory protein (cFLIP), caspase-3 and caspase-8. Three of 8 PNET cell lines tested were susceptible to TRAIL-induced apoptosis. Sensitivity to TRAIL-induced apoptosis did not correlate with mRNA expression of TRAIL receptors or cFLIP. However, all TRAIL-sensitive PNET cell lines expressed caspase-8 mRNA and protein, while none of the five TRAIL-resistant PNET cell lines expressed caspase-8 protein. Treatment with the methyltransferase inhibitor 5-aza-2'-deoxycytidine restored mRNA expression of caspase-8 and TRAIL-sensitivity in formerly TRAIL-resistant PNET cells, suggesting that gene methylation inhibits caspase-8 transcription in these cells. We conclude, that loss of caspase-8 mRNA is an important mechanism of TRAIL-resistance in PNET cells. Treatment with recombinant soluble TRAIL, possibly in combination with methyltransferase inhibitors, represents a promising therapeutic approach for PNET that deserves further investigation.
肿瘤坏死因子相关凋亡诱导配体（TRAIL）是成人恶性胶质瘤及其他多种人类实体瘤模型中凋亡的有效诱导剂，但对正常组织无此作用。为了明确儿童原始神经外胚层脑肿瘤（PNET）中的TRAIL死亡途径，对8种人PNET细胞系进行了TRAIL诱导凋亡的检测。PNET细胞系对TRAIL的敏感性与TRAIL、其激动性受体（TRAIL-R1、TRAIL-R2）和拮抗性受体（TRAIL-R3、TRAIL-R4）、细胞FLICE样抑制蛋白（cFLIP）、半胱天冬酶-3和半胱天冬酶-8的mRNA表达水平相关。所检测的8种PNET细胞系中有3种对TRAIL诱导的凋亡敏感。对TRAIL诱导凋亡的敏感性与TRAIL受体或cFLIP的mRNA表达无关。然而，所有对TRAIL敏感的PNET细胞系均表达半胱天冬酶-8的mRNA和蛋白，而5种对TRAIL耐药的PNET细胞系均不表达半胱天冬酶-8蛋白。用甲基转移酶抑制剂5-氮杂-2'-脱氧胞苷处理可恢复先前对TRAIL耐药的PNET细胞中半胱天冬酶-8的mRNA表达及对TRAIL的敏感性，提示基因甲基化抑制了这些细胞中半胱天冬酶-8的转录。我们得出结论，半胱天冬酶-8 mRNA的缺失是PNET细胞对TRAIL耐药的重要机制。用重组可溶性TRAIL治疗，可能联合甲基转移酶抑制剂，是一种有前景的PNET治疗方法，值得进一步研究。
