Inhibition of N-myc expression and induction of apoptosis by iron chelation in human neuroblastoma cells.
Inhibition of N-myc expression and induction of apoptosis by iron chelation in human neuroblastoma cells.
复制标题
DOI：
--
复制
发表时间：
2001-02
期刊：
影响因子：
11.2
通讯作者：
L. Fan;J. Iyer;S. Zhu;K. Frick;Randal K. Wada;A. Eskenazi;P. Berg;N. Ikegaki;R. Kennett;C. Frantz
中科院分区：
文献类型：
--
作者：
L. Fan;J. Iyer;S. Zhu;K. Frick;Randal K. Wada;A. Eskenazi;P. Berg;N. Ikegaki;R. Kennett;C. Frantz
神经母细胞瘤是儿童时期第二常见的实体恶性肿瘤。肿瘤细胞中扩增的 N-myc 基因的增强表达可能与患者预后不良有关，并可能有助于肿瘤的发生和进展。国家临床研究正在研究使用甲磺酸去铁胺 (DFO)（一种铁螯合剂）治疗神经母细胞瘤。我们通过 TUNEL 分析和 DNA 阶梯分析表明，DFO 会诱导培养的人神经母细胞瘤细胞发生凋亡，在此之前会出现 N-myc 表达下降和一些其他癌基因（上调 c-fos 和下调 c-myb）表达的改变，但管家基因则不然。 N-myc 表达的降低是铁特异性的，但不是由核糖核苷酸还原酶的抑制引起的，因为羟基脲对这种含铁酶的特异性抑制不会影响 N-myc 蛋白水平。核连续和瞬时报告基因表达实验表明，N-myc 表达的减少发生在转录起始水平并通过抑制 N-myc 启动子活性而发生。对神经母细胞瘤细胞系中残留细胞 N-myc 蛋白的量与铁螯合 48 小时后泛半胱天冬酶活性测量的细胞凋亡程度进行比较，发现没有相关性，表明 N-myc 表达的减少不太可能介导细胞凋亡。总之，DFO 螯合细胞铁可能会通过多种途径改变影响恶性表型的多种基因的表达。鉴于 N-myc 过表达在神经母细胞瘤恶性肿瘤中的临床重要性，通过 DFO 降低 N-myc 表达可能可作为当前治疗的辅助手段。
Neuroblastoma is the second most common solid malignancy of childhood. Enhanced expression of the amplified N-myc gene in the tumor cells may be associated with poor patient prognosis and may contribute to tumor development and progression. The use of deferoxamine mesylate (DFO), an iron chelator, to treat neuroblastoma is being investigated in national clinical studies. We show here by TUNEL assay and DNA laddering that DFO induces apoptosis in cultured human neuroblastoma cells, which is preceded by a decrease in the expression of N-myc and the altered expression of some other oncogenes (up-regulating c-fos and down-regulating c-myb) but not housekeeping genes. The decrease in N-myc expression is iron-specific but does not result from inhibition of ribonucleotide reductase, because specific inhibition of this iron-containing enzyme by hydroxyurea does not affect N-myc protein levels. Nuclear run-on and transient reporter gene expression experiments show that the decrease in N-myc expression occurs at the level of initiation of transcription and by inhibiting N-myc promoter activity. Comparison across neuroblastoma cell lines of the amount of residual cellular N-myc protein with the extent of apoptosis measured as pan-caspase activity after 48 h of iron chelation reveals no correlation, suggesting that the decrease in N-myc expression is unlikely to mediate apoptosis. In conclusion, chelation of cellular iron by DFO may alter the expression of multiple genes affecting the malignant phenotype by multiple pathways. Given the clinical importance of N-myc overexpression in neuroblastoma malignancy, decreasing N-myc expression by DFO might be useful as an adjunct to current