miRNA-mediated Stromal Cell Survival under Stress Supports Breast Cancer Growth

描述(申请人提供)：多潜能间充质干细胞(MSCs)在治疗人类退行性疾病和损伤方面具有巨大的潜力。近年来，有关乳腺癌间质生物学的研究表明，间充质干细胞为乳腺肿瘤提供支持间质。然而，在我们对基质细胞在通常在实体瘤中观察到的应激条件下的生存机制的理解上有很大的差距，例如缺氧或营养缺乏。目前可用的治疗策略大多只针对癌细胞，而不是肿瘤相关的间质。事实上，更详细地了解MSC存活所涉及的分子机制以及由此产生的间质支持功能，对于改进乳腺癌治疗靶点的设计和选择至关重要。在这项研究中，在血清剥夺中存活并表现出原始特征的MSC亚群的特性将被用作模型，以了解基质细胞在乳腺癌中的作用，特别是在缺氧或营养剥夺等不利条件下。去血清骨髓间充质干细胞(SD-MSCs)利用自噬功能存活并分泌支持乳腺癌细胞的生存因子IGF-1、TGFb等。自噬是多细胞生物体生长调节、维持动态平衡的重要组成部分。MicroRNAs(MiRNAs)是一种进化保守的短小非编码调控RNA，它在转录后调节多种基因的表达，包括癌基因和肿瘤抑制基因，以及那些调控细胞生存和生长的基因。DROSHA和DICER是miRNA生物发生所必需的重要酶。MiRNAs通过与同源靶标mRNA结合来发挥作用，并促进它们的特异性降解。我们的初步数据揭示了一种将SD-MSC存活与miRNA调控联系起来的新机制，此外还证明了DROSHA和DICER功能的丧失废除了MSCs的分化。这项建议的总体目标是了解miRNAs在调节肿瘤相关基质细胞生存和增强其支持乳腺癌细胞生长功能方面的作用。/S本研究的特定假设是，肿瘤间质可以通过差异调节特定miRNAs的表达而在肿瘤微环境的应激条件下存活，而在肿瘤间质中靶向这些miRNAs将消除它们对乳腺癌发生和发展的促进作用。为了实现这一目标，提出了以下目标：(1)确定特定的miRNA表达谱是否与MSCs在体外应激条件下的存活有关。(2)探讨应激间质细胞及其相关的miRNA通路在促进间质支持乳腺癌细胞生长中的作用。(3)筛选在骨髓间充质干细胞存活过程中起作用的miRNAs，寻找可作为抗癌新靶点的miRNAs。本文提出的研究miRNA途径在基质细胞支持中的作用的实验对于了解基质细胞如何在不利条件下存活并支持其周围的肿瘤细胞具有重要意义。此外，还将确定消灭存活的基质细胞的新的治疗靶点。 公共卫生相关性：这项研究将让我们深入了解间充质干细胞/祖细胞在乳腺癌间质支持中的潜在作用。它还将导致识别与基质细胞在应激和化疗药物下的生存有关的miRNA靶点。识别与基质细胞存活有关的分子通路可能会导致识别耐药乳腺癌的新治疗靶点。

DESCRIPTION (provided by applicant): Multipotential Mesenchymal Stromal cells (MSCs) hold great potential for treating human degenerative diseases and injuries. Recent, studies regarding the biology of breast cancer stroma indicate that mesenchymal stem cells (MSCs) provide the supportive stroma for breast tumors. However, there is a significant gap in our understanding of the survival mechanisms used by stromal cells under stressful conditions normally observed within solid tumors, such as hypoxia or nutrient deprivation. Most of the currently available therapeutic strategies only target the cancer cells and not the tumor-associated stroma. Indeed, a more detailed understanding of the molecular mechanisms involved in MSC survival and the resultant stromal supportive functions, is essential for improving the design and selection of therapeutic targets against breast cancer. In this study, properties of a MSC subpopulation that survive serum deprivation and express primitive characteristics will be used as model to understand role of stromal cells in breast cancers especially during adverse conditions such as hypoxia or nutrient deprivation. The serum deprived MSCs (SD-MSCs) utilize autophagy to survive and secrete survial factors such as IGF-1, TGFb etc that support breast cancer cells. Autophagy is an essential part of growth regulation maintenance of homeostasis in multicellular organism. MicroRNAs (miRNAs) are evolutionary conserved; short non-coding regulatory RNAs that post-transcriptionally modulate gene expression of a variety of genes including oncogenes and tumor suppressors, as well as those regulating cell survival and growth. Drosha and Dicer are important enzymes required for miRNA biogenesis. The miRNAs function by binding to a cognate targets mRNA and facilitates their specific degradation. Our preliminary data uncovered a novel mechanism of linking SD-MSC survival to miRNA regulation, in addition to demonstrating that loss of drosha and dicer function abrogates differentiation in MSCs. The overall goal of this proposal is to understand the role of miRNAs in regulating the survival of tumor-associated stromal cells and in enhancing their supportive function/s towards breast cancer cell growth. The specific hypothesis for this study is the tumor-stroma can survive stressful conditions of the tumor microenvironments by differentially regulating expression of specific miRNAs, and targeting of these miRNAs within the tumor-stroma will abrogate their facilitative effects on breast cancer development and progression. To achieve this goal the following aims are proposed (1) To determine whether a specific miRNA expression profile is associated with the survival of MSCs under stressful conditions in vitro. (2) To investigate the role of stressed stromal cells, and the associated miRNA pathways, in facilitating the stromal supportive functions towards breast cancer cell growth. (3) To delineate the miRNAs that play a role in survival of MSCs and identify those which can be targeted as novel anti-cancer strategies. The experiments proposed here to study the role of miRNA pathway in the stromal cell support will be important to understand how stromal cells survive under adverse conditions and support the tumor cells surrounding them. In addition, novel therapeutic targets to abrogate stromal cell survial will be indentified. PUBLIC HEALTH RELEVANCE: This study will give us insight into the potential role that mesenchymal stem/progenitor cells have in the stromal support of breast cancers. It will also lead to identification of miRNA targets that are involved in the survival of stromal cells under stress and chemotherapeutic drugs. Identification of molecular pathways involved stromal cell survival may lead to identification of new therapeutic targets for resistant breast cancer.