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

描述（由申请人提供）：多能间充质基质细胞（MSC）具有治疗人类退行性疾病和损伤的巨大潜力。 最近，关于乳腺癌间质生物学的研究表明，间充质干细胞（MSC）为乳腺肿瘤提供支持性间质。 然而，我们对基质细胞在实体瘤中通常观察到的应激条件下（如缺氧或营养剥夺）的生存机制的理解存在显着差距。 大多数目前可用的治疗策略仅靶向癌细胞而不是肿瘤相关基质。 事实上，更详细地了解MSC存活的分子机制和由此产生的基质支持功能，对于改善乳腺癌治疗靶点的设计和选择至关重要。 在这项研究中，MSC亚群在血清剥夺中存活并表达原始特征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缺乏等不利条件下。 血清剥夺的骨髓间充质干细胞（serum deprived MSCs，SD-MSCs）通过自噬存活，并分泌IGF-1、TGF β等生存因子支持乳腺癌细胞的生长。 自噬是多细胞生物生长调节和维持体内平衡的重要组成部分. microRNA（miRNAs）是进化上保守的;短的非编码调节RNA，其转录后调节多种基因的基因表达，包括癌基因和肿瘤抑制因子，以及调节细胞存活和生长的基因。 Drosha和Dicer是miRNA生物合成所需的重要酶。 miRNA通过结合同源靶mRNA并促进其特异性降解来发挥功能。 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功能的丧失消除了MSC的分化。 该提案的总体目标是了解miRNA在调节肿瘤相关基质细胞的存活和增强其对乳腺癌细胞生长的支持功能中的作用。 本研究的具体假设是肿瘤基质可以通过差异调节特定miRNA的表达而在肿瘤微环境的应激条件下存活，并且在肿瘤基质内靶向这些miRNA将消除其对乳腺癌发展和进展的促进作用。 为了实现这一目标，提出了以下目标：（1）确定特定的miRNA表达谱是否与体外应激条件下MSC的存活相关。 (2)探讨应激基质细胞及其相关的miRNA通路在促进乳腺癌细胞生长的基质支持功能中的作用。 (3)描述在MSC存活中起作用的miRNAs，并鉴定那些可以作为新的抗癌策略靶向的miRNAs。 本文提出的研究miRNA通路在基质细胞支持中的作用的实验对于理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将是重要的。 此外，新的治疗目标，废除基质细胞存活将被确定。 公共卫生相关性：这项研究将使我们深入了解间充质干/祖细胞在乳腺癌基质支持中的潜在作用。 它还将导致识别参与基质细胞在压力和化疗药物下生存的miRNA靶点。 基质细胞存活分子通路的鉴定可能会导致耐药乳腺癌新的治疗靶点的确定。

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.