MDM2 induces NF-κB/p65 expression transcriptionally through Sp1-binding sites:: a novel, p53-independent role of MDM2 in doxorubicin resistance in acute lymphoblastic leukemia
MDM2 induces NF-κB/p65 expression transcriptionally through Sp1-binding sites:: a novel, p53-independent role of MDM2 in doxorubicin resistance in acute lymphoblastic leukemia
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DOI：
10.1182/blood.v99.9.3367
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发表时间：
2002-05-01
期刊：
影响因子：
20.3
通讯作者：
Zhou, MX
中科院分区：
文献类型：
--
作者：
Gu, LB;Findley, HW;Zhou, MX
MDM2 蛋白被认为通过与 p53 肿瘤抑制蛋白结合并抑制其功能而表现出致瘤活性。或者，MDM2 可能具有除 p53 相互作用以外的致癌作用。在这里，我们报道MDM2可以诱导NF-kappaB p65亚基的表达，这是一种在某些肿瘤细胞中响应化疗而表达的抗凋亡因子。最初，我们注意到B细胞前体急性淋巴细胞白血病（BCP-ALL）患者的白血病骨髓细胞和转染MDM2基因的ALL细胞系（EU-4）中MDM2蛋白的过度表达与p65表达升高和对阿霉素（阿霉素）的体外耐药性相关。通过将 MDM2 基因和 p65 启动子报告基因构建体共转染到 EU-4 细胞中，我们发现瞬时和高水平的 MDM2 表达诱导 p65 启动子活性。在野生型 (wt) p53 存在的情况下，MDM2 通过逆转 p53 介导的 p65 抑制来增加 p65 启动子活性。在 p53 缺失的情况下，MDM2 直接增加 p65 启动子活性。 p65启动子的缺失和突变分析表明，nt -575和-178之间的区域包含第一个和第二个Sp1结合位点，是MDM2激活所必需的。使用染色质免疫沉淀 (CHIP) 和电泳迁移率变动测定 (EMSA) 的进一步研究表明，MDM2 能够直接结合 p65 启动子的 Sp1 位点。我们的研究结果表明，通过诱导 p65 表达，MDM2 在肿瘤发生中具有独立于 p53 的作用，这可能进一步阐明 MDM2 过度表达与儿童 ALL 耐药性疾病之间的关联。 (C) 2002 年，美国血液学会。
MDM2 protein Is thought to exhibit tumorigenic activity by binding to the p53 tumor-suppressor protein and inhibiting its function. Alternatively, MDM2 may have oncogenic roles other than those resulting from p53 interactions. Here we report that MDM2 can induce expression of the p65 subunit of NF-kappaB, which is an antiapoptotic factor expressed in certain neoplastic cells in response to chemotherapy. Initially, we noted that the overexpression of MDM2 protein in leukemic bone marrow cells of patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL), and an ALL cell line (EU-4) transfected with the MDM2 gene was associated with elevated expression of p65 and in vitro resistance to doxorubicin (Adriamycin). By cotransfection of the MDM2 gene and p65-promoter-reporter constructs into EU-4 cells, we found that transient and high-level MDM2 expression induced p65 promoter activity. In the presence of wildtype (wt) p53, MDM2 increased p65 promoter activity by reversing p53-mediated suppression of p65. In the absence of p53, MDM2 directly increased p65 promoter activity. Deletion and mutation analysis of the p65 promoter indicated that the region between nt -575 and -178, which contains the first and second Sp1-binding sites, was required for activation by MDM2. Further studies using chromatin immunoprecipitation (CHIP) and electrophoretic mobility shift assay (EMSA) showed that MDM2 was able to directly bind to the Sp1 site of the p65 promoter. Our findings suggest that by inducing p65 expression, MDM2 has a p53-independent role in tumorigenesis, which may further elucidate the association between MDM2 overexpression and resistant disease in childhood ALL. (C) 2002 by The American Society of Hematology.