MDM2通过调控上皮间质转化影响肿瘤转移的机制研究

Epithelial-mesenchymal transition (EMT) is a critical step in mediating the acquisition of metastatic phenotypes by localized carcinomas. Although metastasis clearly is the most lethal aspect of cancer, our knowledge of the molecular events that govern its development, including those underlying EMT, remain relatively undefined. Thus it is our urgent task to identify the key molecules regulating and promoting EMT, and to develop relevant targeting therapeutic strategies against EMT and metastasis. Amplification of MDM2 gene was reported to predict distant metastasis, with mechanisms need to be elucidated. Our preliminary data showed that MDM2 protein expression level are closely related to EMT, and the MDM2 inhibitor Nutlin-3 could attenuate EMT and decrease the tumor cell migration, implicating its potential of suppressing tumor metastasis. Based on these observations, utilizing Nutlin-3 and the other MDM2 inhibitors as small molecular probes, transfecting the mutant plasmids of MDM2 with different functions, we plan to explore the molecular mechanisms and signaling pathways used by MDM2 to regulate EMT in malignant cells, specifically, the regulation modes between MDM2 and Smad signalling pathways. In addition, gene chips and protein chips will be employed to analyze the signalling cross-talk and networks involved in MDM2 and EMT. Thus the current study will uncovers the new biological functions of MDM2, provides new theoretical evidences for the roles that MDM2 playing in tumor metastasis, promotes the discovery and development of novel targets and agents for inhibiting the tumor metastasis, and contributes to the translational research of MDM2 inhibitors as anti-metastatic agents.

上皮间质转化（EMT）是肿瘤细胞获得转移能力的重要步骤，发现调控EMT发生的关键分子，并开发相应的靶向治疗手段具有重大的理论意义和应用价值。文献报道，MDM2和肿瘤转移密切相关，但其在EMT过程中发挥的作用和机制未见报道。我们的前期研究表明，MDM2表达水平和肿瘤细胞EMT的发生高度相关，且MDM2抑制剂Nutlin-3可有效阻遏EMT，抑制肿瘤细胞迁移运动，具备潜在的抗肿瘤转移效果。申请人将在此基础上，进一步探求MDM2在EMT过程中扮演的角色，以Nutlin-3等MDM2抑制剂为分子探针，转入MDM2不同功能区段的突变质粒，深入研究MDM2和Smad信号通路的交互作用及其对EMT的调控模式，借助芯片技术分析描绘其信号调控网络，从而发现MDM2新的生物学功能，为其在肿瘤转移中的分子地位提供新的理论依据，以期发现新的抗肿瘤转移药物作用靶点，为发展具有自主知识产权的创新药物奠定理论基础。

转移是90%的肿瘤病人死亡的原因。上皮间质转化（EMT）发生于肿瘤转移早期，是肿瘤获得转移能力的重要步骤。因此探寻EMT过程中关键作用分子，并针对其开发靶向治疗手段，可能有利于及肿瘤转移的早期干预，成为抗转移治疗的策略。促癌蛋白MDM2与肿瘤转移显著相关，但是其分子机制有待阐明。.本课题研究了MDM2推动肿瘤转移的分子机制：1）首先明确了临床卵巢囊腺癌病人的肿瘤组织中存在MDM2的高表达且具有临床意义：大部分卵巢囊腺癌组织样本的细胞核、细胞浆中均能观察到不同程度的MDM2阳性着色，而MDM2在正常卵巢组织则呈阴性；卵巢癌组织中的阳性着色程度高于正常卵巢组织，且具有显著性差异；采用χ2检验来进一步分析MDM2在卵巢癌组织中高表达的临床意义，结果表明MDM2的表达水平与肿瘤临床分期相关；2）MDM2诱导细胞运动的能力与其促EMT活性有关，MDM2能够通过上调Slug和Snail的蛋白表达从而抑制E-cadherin的转录；3）MDM2对Smad信号通路具有激活作用：过表达MDM2时其转录活性增加，而采用siRNA技术沉默MDM2表达后，Smads复合物转录活性降低；4）沉默MDM2能抑制TGF-β诱导的EMT和细胞迁移；5）MDM2小分子抑制剂Nutlin-3可通过干预Smad信号通路的激活发挥抗EMT作用，进行发挥抑制肿瘤转移的效果。.综上，本课题研究发现促癌蛋白MDM2的表达与卵巢囊腺癌的临床分期具有相关性，提示MDM2可能作为生物标记物成为卵巢囊腺癌预后评价指标；进一步的机制研究发现MDM2可激活Smad信号通路来促使上皮来源的卵巢癌细胞发生EMT和迁移，同时发现MDM2抑制剂Nutlin-3具有抗EMT活性，这不仅表明 MDM2可以作为潜在抗EMT乃至转移的治疗靶点，同时也为MDM2抑制剂的临床应用提供了新思路。