MTDH regulates Fanconi anemia repair pathway to mediate drug resistance

描述(申请人提供)：细胞耐药性是实体瘤治疗失败的主要原因之一，因此需要确定驱动侵袭性表型的新因素。到目前为止，在许多实体肿瘤中都发现了金属粘附素的过度表达，并与预后不良有关。此外，MTDH的过度表达与转移和抵抗治疗有关，这是侵袭性癌症的两个重要特征。我们最近的一个重要发现是，MTDH作为一种RNA结合蛋白来改变多个mRNAs的翻译，从而确定了MTDH在翻译后基因表达中的潜在作用。这些mRNAs包括Fanconi贫血(FA)途径中的几个DNA修复蛋白。我们在这一应用中的目的是确定mtdh对DNA修复的调节在耐药中的作用。该项目的基本原理是，由于MTDH在多种癌症类型中高度表达，并有助于耐药表型的出现，因此对MTDH如何发挥作用的机械性见解将提供一个强有力的科学框架，从而可以开发MTDH途径靶向治疗。为了验证我们的中心假设，我们提出了三个具体的目标：在目标1中，我们将确定MTDH与特定mRNAs的关联改变DNA损伤反应途径的机制。我们将利用MTDH缺失的癌细胞和MTDH-/-小鼠胚胎成纤维细胞，研究MTDH在mRNA代谢中的作用以及对Rad18、FANCI、FANCD2和其他DNA修复蛋白翻译的调控。我们将继续进行研究，以确定通过mRNA模拟来敲除或破坏MTDH：mRNA复合体是否足以扰乱MTDH对FA途径基因的翻译调节。在目标2中，我们将通过靶向mtdh和DNA修复途径来克服对顺铂的耐药性。我们将评估靶向MTDH和FA DNA修复途径是否可以通过破坏细胞对DNA损伤的反应来提高顺铂的治疗效果。在目标3中，我们将确定MTDH的表达和FA通路的激活在肿瘤对ICL诱导剂耐药性中的作用。研究将包括：1)使用我们存活的肿瘤库中具有良好特征的人子宫内膜肿瘤进行异种移植实验；2)对86名接受ICL诱导剂治疗的晚期子宫内膜癌患者的FFPE肿瘤组织中MTDH和FA途径的免疫组织化学分析。随着研究的顺利完成，我们期望通过MTDH对mRNA稳定性的调节和FA途径蛋白的翻译来了解MTDH的病理功能。这些结果有望产生重要的积极影响，因为它们将为MTDH过度表达与治疗耐药的相关性提供强有力的机制基础，并为未来MTDH靶向治疗的发展奠定基础。

DESCRIPTION (provided by applicant): Cellular resistance is one of the major causes of therapeutic failure for solid tumors, thus highlighting the need to identify novel factors driving aggressive phenotypes. Overexpression of metadherin (MTDH, also known as AEG-1 and LYRIC) has been documented in numerous solid tumors to date and correlates with poor prognosis. Moreover, MTDH overexpression has been implicated in metastasis and resistance to therapy, two important hallmarks of an aggressive cancer. We recently made the important discovery that MTDH acts as an RNA binding protein to alter translation of multiple mRNAs, thus identifying a potential role for MTDH in post- translational gene expression. These mRNAs include several DNA repair proteins in the Fanconi anemia (FA) pathway. Our objective in this application is to determine the role of MTDH regulation of DNA repair in resistance to therapy. The rationale for this project is that because MTDH is highly expressed in multiple cancer types and contributes to the emergence of a resistant phenotype, mechanistic insights into how MTDH functions will offer a strong scientific framework whereby MTDH pathway targeted therapies can be developed. To test our central hypothesis, we propose three specific aims: In Aim 1, we will identify mechanisms by which MTDH association with specific mRNAs alters the DNA damage response pathway. Using MTDH-deficient cancer cell lines and MTDH-/- mouse embryonic fibroblasts, we will study the role of MTDH in mRNA metabolism and control of translation of Rad18, FANCI, FANCD2 and other DNA repair proteins. We will extend studies to determine if MTDH knockdown or disruption the MTDH:mRNA complex by mRNA mimetics are sufficient to perturb MTDH translational regulation of FA pathway genes. In Aim 2, we will overcome resistance to cisplatin by targeting MTDH and the DNA repair pathway. We will evaluate whether targeting MTDH and the FA DNA repair pathway can increase the therapeutic efficacy of cisplatin via disruption of the cellular response to DNA damage. In Aim 3, we will determine the effect of MTDH expression and FA pathway activation on resistance to ICL-inducing agents in cancer. Studies will include 1) xenograft experiments using well-characterized human endometrial tumors from our viable tumor bank; and 2) immunohistochemical analysis of the MTDH and FA pathway in FFPE tumor tissues from 86 advanced endometrial cancer patients treated with ICL-inducing agents. Upon the successful completion of the proposed research, it is our expectation that we will understand the pathological function of MTDH through its regulation of mRNA stability and translation of FA pathway proteins. These results are expected to have an important positive impact because they will provide a strong mechanistic basis for the correlation of MTDH overexpression with therapeutic resistance and serve as a foundation for the future development of MTDH-targeted therapies.