UNCOVERING THE MECHANISMS OF OSTEOSARCOMA METASTASIS SUPPRESSION BY MTBP

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 我们的长期目标是阐明Mdm 2-p53通路在体内对肿瘤发展的影响，这是发展减毒癌症治疗方案的必要先决条件。p53作为肿瘤抑制因子发挥作用，并通过激活许多下游靶点如p21、BAX、GADA、GADD 45作为转录因子1来发挥这一功能。Mdm 2是通过物理结合和诱导p53降解的p53的主要抑制剂2。p53基因在超过50%的肿瘤中突变，并且Mdm 2在多种肿瘤中高度表达，强调了Mdm 2-p53途径在肿瘤发展中的重要性3-6。应该注意的是，相当数量的肿瘤具有野生型p53和Mdm 2过表达。有趣的是，与肿瘤中仅有突变型p53的患者相比，已知一些p53基因突变且Mdm 2过表达的肿瘤患者具有较差的预后7，8。这些结果表明，Mdm 2在肿瘤发展中也具有p53非依赖性作用。最近，发现Mdm 2与其他肿瘤抑制因子如Rb、PML和p73抑制性相互作用，这可能有助于Mdm 2在肿瘤发展中的p53非依赖性作用9 -15。可以假设任何影响Mdm 2功能的蛋白质都可能对肿瘤的发展产生影响。 Mdm 2结合蛋白（MTBP）由Boyd MT等人16使用酵母双杂交系统以Mdm 2作为诱饵分离。MTBP的过表达导致细胞周期的G1期阻滞，但这种作用被同时过表达的Mdm 2所抵消。我们的工作假设是MTBP在肿瘤的发展和转移中起着关键作用。这一假设是基于我们使用常规mtbp敲除小鼠的初步结果，我们观察到（1）30%的mtbp杂合小鼠在22个月内自发地发生肿瘤，（2）mtbp和p53双杂合敲除小鼠发生转移性骨肉瘤。基于这些观察结果，该建议的重点是MTBP在骨肉瘤转移中的作用以及该蛋白的功能特征。具体目标旨在全面评估MTBP的新功能，特别是在骨肉瘤转移中的功能。 目标1.描述由mtbp缺失引起的骨肉瘤。 目标二。产生和表征具有条件性mtbp和/或p53敲除等位基因的小鼠，特别是在成骨细胞中。 目标3。分离MTBP相互作用蛋白。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Our long-term goal is to elucidate the impact of the Mdm2-p53 pathway in vivo on tumor development as a necessary prerequisite to the development of therapeutic protocols for attenuating cancer. p53 functions as a tumor suppressor and exerts this function by activating numerous downstream targets such as p21, BAX, PUMA, GADD45 as a transcription factor1. Mdm2 is a major inhibitor of p53 through physical binding and induction of p53 degradation2. The p53 gene is mutated in more than 50% of tumors, and Mdm2 is highly expressed in a variety of tumors, stressing the importance of the Mdm2-p53 pathway in tumor development 3-6. It should be noted that a significant number of tumors have wild-type p53 with Mdm2 over-expression. Interestingly, some patients with tumors in which p53 gene is mutated and Mdm2 is over-expressed are known to have a poorer prognosis, compared to patients with mutant p53 alone in tumors7, 8. These results suggest that Mdm2 also has p53-independent roles in tumor development. Recently, Mdm2 is found to inhibitory interact with other tumor suppressors such as Rb, PML, and p73, which may contribute to p53-independent roles of Mdm2 in tumor development9-15. One can assume that any proteins that affect Mdm2 function may have an impact on tumor development. Mdm2 Binding Protein (MTBP) was isolated by Boyd MT et al.16 using the yeast two hybrid system with Mdm2 as bait. Over-expression of MTBP causes G1 arrest of cell cycle, but the effect is nullified by simultaneous over-expression of Mdm2. Our working hypothesis is that MTBP plays a critical role in tumor development and metastasis. This hypothesis is based on our preliminary results using a conventional mtbp knockout mouse in which we observed that (1) 30% of mtbp heterozygous mice spontaneously developed tumors within 22 months, and (2) doubly heterozygous knockout mice for mtbp and p53 developed metastatic osteosarcomas. Based on these observations, the focus of this proposal is on the roles of MTBP in osteosarcoma metastasis and the functional characterization of this protein. The specific aims are designed to provide a comprehensive assessment of novel functions of MTBP, especially in osteosarcoma metastasis. Aim 1. To characterize osteosarcomas induced by loss of mtbp. Aim 2. To generate and characterize mice with conditional mtbp and/or p53 knockout alleles, specifically in osteoblasts. Aim 3. To isolate MTBP interacting proteins.