SOX7在乳腺癌中调控机制的研究

Recent studies suggest a tumor suppressive role of SOX7 in oncogenesis. However, many gaps still exist regarding how SOX7 is regulated and whether SOX7-mediated gene transcription plays a role in the tumor suppressive activity of SOX7. In our preliminary studies, we found that SOX7 expression can be potentially regulated by microRNAs and ectopic SOX7 expression in breast cancer could significantly alter the expression of genes involved in cell death, survival, development, mobility, and proliferation. Based on these observations, we hypothesize that microRNAs play an important role in downregulating SOX7 in breast cancer; SOX7-mediated gene expression contributes to its tumor suppressive activity. Our objectives include dissecting the mechanisms of the SOX7-related regulatory network and determining the biological importance of SOX7-mediated tumor suppression in breast cancer pathogenesis. We have two specific aims to test these hypotheses. In Aim 1, we will determine the contribution of microRNAs to SOX7 downregulation in breast cancer. In this aim, we will study whether SOX7 downregulation is regulated by the microRNAs determined in our preliminary studies and examine the expression correlation of these microRNAs with SOX7 in breast cancer. In Aim 2, we will investigate SOX7 target genes and their contribution to SOX7-mediated tumor suppression. In this aim, we will validate the regulation of these candidate target genes by SOX7, assess their roles in SOX7-mediated tumor suppression, and examine their correlation with SOX7 in breast cancer. The innovation of this proposal lies in its innovative preliminary data and specific aims. We propose to study the contribution of microRNAs to SOX7 reduction, its prognostic potential, and its mediated gene expression to breast cancer oncogenesis. None of these studies have been explored previously. Our project will unravel mechanisms of both SOX7 upstream and downstream regulation, and its potential role in breast cancer prognosis. The success of this study will advance our understanding of the regulation of SOX7 as a novel tumor suppressor and provide insight into the intervention of breast cancer progression through reactivating SOX7 and its regulated tumor suppressive network.

抑癌基因SOX7在肿瘤中低表达的机制还没有被研究透彻，癌细胞中SOX7的调控基因还未被探索。我们的前期研究表明，microRNA有调节SOX7的可能性，乳腺癌细胞中外源SOX7可改变调节细胞存活，迁移和增殖基因的表达。因此我们推测：乳腺癌中microRNA抑制SOX7的表达，SOX7调节的基因对其抑癌功能很重要。本项目拟研究以下内容：1. 利用报告载体和对内源基因表达的控制，阐明microRNA对SOX7的调节。同时，测定它们在乳腺癌中表达的相关性。2. 确定SOX7对新发现的四个潜在靶基因的控制，并研究它们对于SOX7抑癌活性的贡献和与SOX7表达的相关性。项目的创新处是，microRNA对SOX7的调控还研究甚少，SOX7调节的基因表达对其抑癌活性的作用尚未被探索。我们研究的目的是解析SOX7上下游调节的机制，为在乳腺癌治疗中激活SOX7表达或刺激其调节的抑癌通路提供理论依据。

在多种癌症中，SOX7发挥了抑癌基因作用。同时，SOX7下调在多种晚期癌症中出现，并与病人的不良预后相关联。在肿瘤细胞中，外源表达SOX7阻碍细胞生长并促进细胞凋亡，而降低SOX7表达会增强非肿瘤细胞克隆形成的能力。虽然有报道指出SOX7对β-catenin的稳定性和功能有负调节作用，但SOX7抑制肿瘤形成的分子机制，尤其做为转录因子如何抑制细胞癌变，尚未被阐明。在我们的前期研究中，microRNA有调节SOX7的可能性，乳腺癌细胞中外源SOX7可改变很多调节细胞存活，迁移和增殖基因的表达。因此，我们设想，乳腺癌中microRNA抑制SOX7的表达，SOX7的调节基因对其抑癌功能很重要。检测这些假想的研究内容及重要结果包括：1. 利用报告载体和对内源基因表达的控制，阐明microRNA对SOX7的调节。同时，测定它们在乳腺癌中表达的相关性：我们发现，miR-9和miR-181a对SOX7 3’-UTR的报告载体有明显抑制作用，但是对内源SOX7的抑制作用并不明显。通过抑制SOX7启动子甲基化，也未检测到microRNA对内源SOX7明显抑制。因此，其它未知机制对SOX7表达的抑制更为重要。在700多例乳腺癌样品中，miR-9和miR-181a分别与SOX7表达有较弱的但是有统计学意义的反向对应关系。2. 确定SOX7对新发现的四个潜在靶基因的控制，并研究它们对于SOX7抑癌活性的贡献和与SOX7表达的相关性：利用多种实验方法，确定SPRY1和 SLIT2为SOX7激活的基因，而TRIB3和MTHFD2为SOX7抑制的基因。在诱导SOX7并分别逆向表达这些基因时，乳腺癌细胞增值均有恢复，但敲低SPRY1或外源表达MTHFD2在较大程度上补救细胞增殖，表明这两个基因是SOX7在乳腺癌中的主要靶基因。同时，在1100多例乳腺癌样品，发现了SOX7与SPRY1和 SLIT2的正向对应关系，SOX7与TRIB3和MTHFD2的反向对应关系。本项目的创新点包括：首次揭示microRNA的调控并不是SOX7低表达的主要因素，判定SOX7 3’-UTR结构或其它因素对SOX7的下调更为重要；首次在肿瘤细胞中揭示了受SOX7调控的基因。这些结果，解析了乳腺癌中调节SOX7基因表达的分子机制，尤其是首次阐述了肿瘤细胞中SOX7的靶基因及其在SOX7抑癌信号通路中所发挥的作用，这为乳腺癌

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