HER2 and the link between inflammation and cancer stem cells

描述(申请人提供)：许多人类肿瘤，包括乳腺癌，表现出一种层次化的组织结构，其中具有干细胞特性的肿瘤细胞子集驱动肿瘤的生长和转移。最近的研究表明，癌症干细胞(CSCs)除了受外源性炎症途径的调控外，还受内在的自我更新途径的调控。HER2的过度表达可以增加CSC的数量，但其潜在的分子机制仍不清楚。我们系统地解剖了HER2下游的信号通路，发现NFkB和STAT3通路对CSCs的自我更新最重要。有趣的是，NFkB和STAT3的激活不是由HER2下游的信号分子直接介导的，如MAPK或PI3K/AKT激酶，而是由HER2诱导的白介素1(IL-1)和白介素6(IL-6)细胞因子介导的。IL-1是一种广为人知的促炎细胞因子，可以诱导包括IL-6在内的一系列细胞因子的表达，从而促进和维持炎症。因此，我们假设HER2对IL-1的诱导是炎症和肿瘤干细胞之间的重要联系，肿瘤干细胞和间质细胞启动一系列细胞因子来调节体内的CSC群体。为了验证这一假设，我们将进行以下具体操作 目标。在目标1中，我们将阐明HER-2调控乳腺癌细胞IL-1和IL-6表达的分子机制。通过一系列的生化手段，我们将首先确定在乳腺癌细胞中诱导IL-1表达的关键的HER2下游信号通路，并研究IL-1是否反过来激活IL-6的表达。在目标2中，我们将研究HER2诱导的IL-1和IL-6信号在肿瘤干细胞维持和调节中的作用和机制。我们将使用重组蛋白和击倒细胞模型来研究IL-1诱导的NFkB信号和IL-6诱导的STAT3信号之间的相互作用如何调节CSC群体。在目的3中，我们将探讨IL-1和IL-6在HER2诱导的乳腺肿瘤发生中的来源和作用。我们将MMTV-Her2转基因小鼠与IL-1和IL-6基因敲除小鼠模型杂交，研究这两种细胞因子在Her2/neu诱导的肿瘤发生发展中的作用。这项研究的成功将有助于我们理解HER2诱导的IL-1和IL-6细胞因子在体外和体内CSC群体的产生和维持中的机制和功能。

DESCRIPTION (provided by applicant): Many human tumors, including breast cancer, display a hierarchical organization in which a subset of tumor cells with stem cell properties drives tumor growth and metastasis. Recent studies have shown that cancer stem cells (CSCs) are regulated by intrinsic self-renewal pathways in addition to extrinsic inflammatory pathways. Overexpression of HER2 has been shown to increase the CSC population but the underlying molecular mechanism is still largely unknown. We have systematically dissected the HER2-downstream signaling pathways and found that the NFkB and STAT3 pathways are the most important for self-renewal of CSCs. Interestingly, activation of NFkB and STAT3 is not directly mediated by signaling molecules immediately downstream of HER2, such as MAPK or PI3K/AKT kinases, but instead is mediated by HER2-induced interleukin-1 (IL-1) and interleukin-6 (IL-6) cytokines. IL-1 is a well-known proinflammatory cytokine that can induce the expression of a cascade of cytokines including IL-6 to propagate and sustain inflammation. Therefore, we hypothesize that HER2 induction of IL-1 serves as an important link between inflammation and cancer stem cells that switches on a cascade of cytokines in both tumor and stromal cells to regulate the CSC population in vivo. To test this hypothesis, we will pursue the following specific aims. In Aim 1, we will elucidate the molecular mechanism by which HER-2 regulates the expression of IL-1 and IL-6 in breast cancer cells. Using a series of biochemical approaches, we will first identify the key HER2-downstream signaling pathways responsible for induction of IL-1 expression in breast cancer cells and address whether IL1 in turn activates IL- 6 expression. In aim 2, we will study the function and mechanism of HER2-induced IL-1 and IL-6 signaling in the maintenance and regulation of cancer stem cells. We will use recombinant proteins and knockdown cell models to study how the interplay between IL-1-induced NFkB signaling and IL-6-induced STAT3 signaling regulates the CSC population. In aim 3, we will investigate the sources and functions of IL-1 and IL-6 in promotion of HER2-induced mammary tumorigenesis. We will cross MMTV-Her2 transgenic mice with IL-1 and IL-6 knockout mice models to study the functions of these two cytokines in Her2/neu-induced tumor onset and progression. Successful completion of this study will help us understand the mechanism and functions of HER2-induced IL1 and IL6 cytokines in the generation and maintenance of the CSC population both in vitro and in vivo.