Transcriptional Repression of SKP2 Is Impaired in MYCN-Amplified Neuroblastoma
Transcriptional Repression of SKP2 Is Impaired in MYCN-Amplified Neuroblastoma
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DOI：
10.1158/0008-5472.can-09-1245
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发表时间：
2010-05-01
期刊：
影响因子：
11.2
通讯作者：
Westermann, Frank
中科院分区：
文献类型：
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作者：
Muth, Daniel;Ghazaryan, Seda;Westermann, Frank
细胞周期调节因子SKP 2在各种癌症中过表达，并在参与肿瘤细胞去分化的p27降解中发挥关键作用。对于导致肿瘤细胞中SKP 2转录控制受损的机制知之甚少。我们使用神经母细胞瘤作为模型来研究SKP 2调节，因为SKP 2转录水平随着神经母细胞瘤亚型的侵袭性而逐渐增加。在MYCN扩增的神经母细胞瘤中发现SKP 2水平最高。因此，我们发现MYCN扩增细胞中SKP 2核心启动子活性高出5.5倍（范围，2-9.5）。MYCN扩增细胞中较高的SKP 2核心启动子活性是通过转录起始位点的确定区域介导的。该区域包括一个特定的E2 F结合位点，使SKP 2的激活在很大程度上不依赖于通过SP1/ELK-1位点整合的促有丝分裂信号。我们通过染色质免疫沉淀显示，通过MYCN扩增细胞中的转录起始位点的SKP 2激活与结合到SKP 2启动子的pRB-E2 F1复合物的低丰度相关。通过使用CDK 4的选择性小化合物抑制剂恢复pRB活性，可以在MYCN扩增的细胞中重新建立通过这种调节机制对SKP 2的转录控制。相比之下，阿霉素或nutlin-3治疗-均导致p53-p21激活-或CDK 2抑制对MYCN扩增细胞中的SKP 2调节没有影响。总之，这意味着MYCN扩增的神经母细胞瘤细胞中MYCN蛋白水平失调通过CDK 4诱导激活SKP 2，消除与SKP 2启动子结合的抑制性pRB-E2 F1复合物。Cancer Res; 70（9）; 3791-802. (C)2010年AACR。
The cell cycle regulator, SKP2, is overexpressed in various cancers and plays a key role in p27 degradation, which is involved in tumor cell dedifferentiation. Little is known about the mechanisms leading to impaired SKP2 transcriptional control in tumor cells. We used neuroblastoma as a model to study SKP2 regulation because SKP2 transcript levels gradually increase with aggressiveness of neuroblastoma subtypes. The highest SKP2 levels are found in neuroblastomas with amplified MYCN. Accordingly, we found 5.5-fold (range, 2-9.5) higher SKP2 core promoter activity in MYCN-amplified cells. Higher SKP2 core promoter activity in MYCN-amplified cells is mediated through a defined region at the transcriptional start site. This region includes a specific E2F-binding site that makes SKP2 activation largely independent of mitogenic signals integrated through the SP1/ELK-1 site. We show by chromatin immunoprecipitation that SKP2 activation through the transcriptional start site in MYCN-amplified cells is associated with the low abundance of pRB-E2F1 complexes bound to the SKP2 promoter. Transcriptional control of SKP2 through this regulatory mechanism can be re-established in MYCN-amplified cells by restoring pRB activity using selective small compound inhibitors of CDK4. In contrast, doxorubicin or nutlin-3 treatment-both leading to p53-p21 activation-or CDK2 inhibition had no effect on SKP2 regulation in MYCN-amplified cells. Together, this implies that deregulated MYCN protein levels in MYCN-amplified neuroblastoma cells activate SKP2 through CDK4 induction, abrogating repressive pRB-E2F1 complexes bound to the SKP2 promoter. Cancer Res; 70(9); 3791-802. (C) 2010 AACR.