LaRusch Gretchen A, Jackson Mark W, Dunbar James D, Warren Robert S, Donner David B, Mayo Lindsey D
Department of Radiation Oncology, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio, USA.
Cancer Res. 2007 Jan 15;67(2):450-4. doi: 10.1158/0008-5472.CAN-06-2710.
Hdm2 is elevated in numerous types of malignancies and is thought to impede the function of wild-type p53. Reactivation of p53 by disrupting the association with Hdm2 was the impetus for the development of Nutlin3. Although regulation of p53 has been the central focus of Hdm2 activity, it also binds other proteins through its p53-binding domain. Here, we show that hypoxia-inducible factor 1alpha (HIF1alpha) binds to Hdm2 in the domain designated to bind p53. HIF1alpha and p53 share a conserved motif that is required to bind Hdm2. Distinct complexes form between Hdm2-HIF1alpha and Hdm2-p53 as determined by immunoprecipitation of nuclear extracts and in vitro. The Hdm2 antagonist Nutlin3 prevents the association between Hdm2 and HIF1alpha. The vascular endothelial growth factor (VEGF) gene is a transcriptional target of HIF1alpha, and under normoxic or hypoxic conditions, Hdm2 increases HIF1alpha activity to induce VEGF production. Blocking the association of Hdm2 and HIF1alpha by Nutlin3, or ablating Hdm2 expression, diminished the level of VEGF under conditions of normoxia or hypoxia. Our findings establish a unique role for Nutlin3 in attenuating VEGF induction by preventing the association of Hdm2 with HIF1alpha.
Hdm2在多种恶性肿瘤中表达上调，被认为会阻碍野生型p53的功能。通过破坏与Hdm2的结合来重新激活p53是Nutlin3研发的动力。虽然p53的调控一直是Hdm2活性的核心焦点，但它也通过其p53结合结构域与其他蛋白质结合。在此，我们表明缺氧诱导因子1α（HIF1α）在指定与p53结合的结构域中与Hdm2结合。HIF1α和p53共享一个与Hdm2结合所需的保守基序。通过对核提取物进行免疫沉淀和体外实验确定，Hdm2-HIF1α和Hdm2-p53之间形成了不同的复合物。Hdm2拮抗剂Nutlin3可阻止Hdm2与HIF1α之间的结合。血管内皮生长因子（VEGF）基因是HIF1α的转录靶点，在常氧或缺氧条件下，Hdm2会增加HIF1α的活性以诱导VEGF产生。通过Nutlin3阻断Hdm2与HIF1α的结合，或消除Hdm2的表达，可降低常氧或缺氧条件下VEGF的水平。我们的研究结果确立了Nutlin3在通过阻止Hdm2与HIF1α结合来减弱VEGF诱导方面的独特作用。
