Lu Xiaohong, Pearson Andrew, Lunec John
Cancer Research Unit, Northern Institute for Cancer Research, University of Newcastle upon Tyne, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK.
Cancer Lett. 2003 Jul 18;197(1-2):125-30. doi: 10.1016/s0304-3835(03)00096-x.
The transcription factor and proto-oncogene MYCN is reviewed as a potential specific target for cancer therapy. Amplification of MYCN is frequently found in a number of advanced-stage tumours, including neuroblastoma (25%), small cell lung cancers (7%), alveolar rhabdomyosarcoma and retinoblastoma. It is associated with rapid tumour progression and poor outcome in human neuroblastoma. MYCN is a member of the myc family of proto-oncogenes which encode nuclear proteins that form heterodimers with MAX protein through their conserved HLHZip domains. The MYC/MAX complexes transactivate a number of MYC-target genes in a sequence-specific manner. MYC-MAX interaction is essential for MYC-induced cell cycle progression, cellular transformation, and transcriptional activation. A causal link between the transformed phenotype and MYCN has been established by a range of in vitro and in vivo studies, including a transgenic model of neuroblastoma in which MYCN overexpression is targeted to neuronal tissue by the use of a tyrosine hydroxylase promoter. Downregulation of MYCN expression either by antisense treatment targeted against MYCN mRNA or by retinoids has been shown to decrease proliferation and/or induce neuronal differentiation of neuroblastoma cells. Inhibition of MYC-MAX dimerisation by small-molecule antagonists has recently been shown to interfere with MYC-induced transformation of chick embryo fibroblasts, indicating that functional inhibitors of the MYC family of oncoproteins have potential as therapeutic agents. Finally, we describe the development and validation of a functional MYCN reporter gene assay using neuroblastoma cells (NGP) which have been stably transfected with a luciferase gene construct under control of the ornithine decarboxylase gene promoter. This assay has been used for a pilot screen of 2800 compounds from the Cancer Research-UK collection, identifying five compounds showing a consistent significant reduction of MYCN-dependent luciferase activity (>50%) in repeated screens. This cell-based, MYCN reporter gene assay will be scaled up for high throughput screens of compound libraries and will aid in the future development of specific therapeutic strategies in neuroblastoma and other tumours in which MYCN amplification has been implicated.
转录因子及原癌基因MYCN被视作癌症治疗的一个潜在特异性靶点。MYCN的扩增常见于多种晚期肿瘤，包括神经母细胞瘤（25%）、小细胞肺癌（7%）、肺泡横纹肌肉瘤及视网膜母细胞瘤。它与人类神经母细胞瘤的肿瘤快速进展及不良预后相关。MYCN是原癌基因myc家族的成员之一，该家族编码的核蛋白通过其保守的HLHZip结构域与MAX蛋白形成异源二聚体。MYC/MAX复合物以序列特异性方式反式激活多个MYC靶基因。MYC-MAX相互作用对于MYC诱导的细胞周期进程、细胞转化及转录激活至关重要。一系列体外和体内研究已证实转化表型与MYCN之间存在因果联系，包括一种神经母细胞瘤转基因模型，其中通过使用酪氨酸羟化酶启动子使MYCN在神经元组织中过表达。针对MYCN mRNA的反义治疗或视黄酸处理均可下调MYCN表达，进而减少神经母细胞瘤细胞的增殖和/或诱导其神经元分化。最近研究表明，小分子拮抗剂抑制MYC-MAX二聚化可干扰MYC诱导的鸡胚成纤维细胞转化，这表明myc家族癌蛋白的功能性抑制剂具有作为治疗药物的潜力。最后，我们描述了一种使用神经母细胞瘤细胞（NGP）的功能性MYCN报告基因检测方法的开发与验证，这些细胞已被稳定转染了在鸟氨酸脱羧酶基因启动子控制下的荧光素酶基因构建体。该检测方法已用于对英国癌症研究中心收集的2800种化合物进行初步筛选，在重复筛选中鉴定出5种化合物，它们能持续显著降低MYCN依赖性荧光素酶活性（>50%）。这种基于细胞的MYCN报告基因检测方法将扩大规模用于化合物文库的高通量筛选，并将有助于未来开发针对神经母细胞瘤及其他涉及MYCN扩增的肿瘤的特异性治疗策略。
