p53-independent Role of MDM2, TGFb Resistance and Cancer

转化生长因子β是一种功能性细胞因子，与肿瘤抑制有关。转化生长因子β对正常细胞和早期肿瘤细胞的生长有抑制作用。然而，作为对转移的适应，晚期肿瘤往往对转化生长因子β耐药。肿瘤对转化生长因子β耐药的机制还不完全清楚。我们的结果表明，癌基因MDM2可能是TGFbeta耐药的原因，其机制不依赖于P53，很可能是通过干扰Rb/3E2F功能。虽然MDM2和P53之间的相互作用已经被很好地描述，但对MDM2的P53非依赖性致癌活性知之甚少。这项应用的目的是进一步探索MDM2在人类肿瘤发展过程中对转化生长因子β耐药和肿瘤发生的不依赖于p53的作用。首先，将进行突变分析，以确定MDM2的哪些区域和活性对于其赋予TGFbeta抗性的能力是必不可少的。其次，将在人类肿瘤细胞系中分析在转化生长因子β耐药和肿瘤发生中对MDM2非p53活性的要求，这些细胞系具有涉及MDM2过度表达的明确基因改变。最后，反义MDM2抑制剂将被用来检测在人类乳腺癌中TGFbeta耐药与MDM2表达的独立性。这些研究不仅将提供对肿瘤中导致TGFβ敏感性丧失的不同途径的见解，而且还将揭示MDM2在肿瘤发生中的新作用。

TGFbeta is a functional cytokine that has been implicated in tumor suppression. The growth of normal cells and early stage tumor cells is inhibited by TGFbeta. However, late stage tumors often become refractory to TGFbeta, as an adaptation to metastasis. The mechanisms for TGFbeta resistance in humor tumors has not been completely understood. Our results indicate that an oncogene, mdm2, is a likely cause of TGFbeta resistance through a p53-independent mechanism, most likely by interference with the Rb/3E2F functions. While the interaction between MDM2 and p53 has been well characterized, little is known about the p53-independent oncogenic activity of MDM2. The goal of this application is to further explore the p53-independent roles of MDM2 in TGFbeta resistance and tumorigenesis during human tumor development. First, mutational analysis will be performed to determine which regions and activities of MDM2 are essential for it ability to confer TGFbeta resistance. Second, the requirement for the p53- independent activity of MDM2 in TGFbeta resistance and tumorigenesis will e analyzed in human tumor cell lines created with defined genetic alterations involving MDM2 over-expression. Finally, anti-sense MDM2 inhibitors will be used to examine the independence of TGFbeta resistance on MDM2 expression in human breast carcinomas. These studies will not only offer insights into the diverse pathways leading to the loss of TGFbeta sensitivity in tumors, but also reveal novel roles of MDM2 in tumorigenesis.