Role of IFN inducible transmembrane protein 1 in AI-resistant breast cancer

 描述(由申请人提供) 大多数乳腺癌依靠雌激素来刺激其生长和存活。雌激素是由前体荷尔蒙通过芳香酶酶产生的，其作用可被芳香酶抑制剂(AIs)阻断。不幸的是，大约40%的乳腺癌患者对这种治疗方法有抵抗力，尽管循环中的雌激素耗尽，但他们的乳腺肿瘤要么继续生长，要么复发。人工智能抵抗的确切原因尚不清楚。我们的实验室旨在确定使乳腺癌细胞在雌激素耗尽的条件下存活的机制。我们之前已经报道了一株AI耐药的乳腺癌细胞株MCF-7：5C，它是在无雌激素条件下从雌激素依赖细胞系MCF-7中分离出来的。MCF-7：5C细胞具有高度侵袭性，过度表达干扰素刺激基因，包括干扰素诱导的跨膜蛋白1(IFITM1)。我们发现IFITM1在这个AI耐药细胞模型和从患者分离的AI耐药乳腺肿瘤中都过表达。IFITM1通常不由细胞表达，只有在干扰素(IFN)刺激下才会产生。机制研究表明，干扰素α的升高通过干扰素α受体(IFNAR)驱动IFITM1的表达。最值得注意的是，IFITM1表达的缺失导致了耐AI的MCF-7：5C细胞的死亡，这表明抑制这一途径可能具有治疗前景。我们假设，来自IFNAR的JAK/STAT信号利用IFITM1启动子中特定的干扰素敏感反应元件(ISRE)来驱动表达，并且IFITM1的过表达使耐AI的MCF-7：5C细胞在体内保持其侵袭性表型。为了解决这一假设，我们提出了以下具体目标：目标1：确定JAK/STAT信号刺激AI耐药乳腺癌细胞中IFITM1过表达的机制。目的2：确定体内过表达IFITM1是否为AI耐药细胞提供了功能优势。在目标1中，我们将利用染色质免疫沉淀法(ChIP)和荧光素酶报告基因来确定哪些转录因子驱动IFITM1的过表达，并研究IFITM1启动子中使用的基序。在目标2中，我们将利用可诱导的慢病毒表达载体来产生我们的细胞系的功能克隆的得失。将使用浸润性乳腺癌进展的小鼠导管内(Mind)模型来确定IFITM1表达变化对AI敏感和AI耐药乳腺癌细胞的侵袭和致瘤潜力的影响。这项研究获得的见解将进一步加深我们对干扰素信号和干扰素刺激基因在乳腺癌预后和治疗抵抗中所起作用的理解。拟议的项目还将为我未来成为该领域的内科科学家奠定基础 肿瘤学博士。

 DESCRIPTION (provided by applicant) The majority of breast cancers rely on estrogen to stimulate their growth and survival. Estrogen is produced from precursor hormones by the aromatase enzyme, whose action can be blocked with aromatase inhibitors (AIs). Unfortunately ~40% of breast cancer patients are resistant to this treatment and their breast tumors either continue to grow or recur despite depletion of circulating estrogen. The precise cause of AI-resistance is not known. Our lab aims to determine the mechanisms that allow breast cancer cells to survive in estrogen- depleted conditions. We have previously reported the generation of an AI-resistant breast cancer cell line, MCF-7:5C, which was isolated under estrogen-free conditions from the estrogen-dependent cell line MCF-7. The MCF-7:5C cell line is highly aggressive and overexpresses several interferon stimulated genes including, interferon inducible transmembrane protein 1 (IFITM1). We have found that IFITM1 is overexpressed in both this AI-resistant cell model and AI-resistant breast tumors isolated from patients. IFITM1 is not normally expressed by cells and is only produced following stimulation with interferons (IFNs). Mechanistic studies have revealed that elevated IFNα drives IFITM1 expression through the IFNα receptor (IFNAR). Most notably, loss of IFITM1 expression induces the death of the AI-resistant MCF-7:5C cells, suggesting that inhibiting this pathway might hold therapeutic promise. We hypothesize that JAK/STAT signaling from IFNAR utilizes specific interferon sensitive response elements (ISRE) in the IFITM1 promoter to drive expression and that IFITM1 overexpression allows the AI-resistant MCF-7:5C cells to maintain their aggressive phenotype in vivo. In order to address this hypothesis we propose the following specific aims: Aim 1: Identify the mechanism by which JAK/STAT signaling stimulates IFITM1 overexpression in AI-resistant breast cancer cells. Aim 2: Determine whether IFITM1 overexpression provides a functional advantage to AI-resistant cells in vivo. In aim 1 we will utilize chromatin immunoprecipitation (CHIP) assays and luciferase reporters to determine which transcription factors drive IFITM1 overexpression and to investigate the motifs utilized in the IFITM1 promoter. In aim 2, we will utilize inducible lentivirial expression vectors to produce gain and loss of function clones of our cell lines. The impact of altered IFITM1 expression on the invasive and tumorigenic potential of AI-sensitive and AI- resistant breast cancer cells will be determined using the mouse intraductal (MIND) model of invasive breast cancer progression. The insights gained from this study will further our understanding of the role that IFN signaling and IFN stimulated genes play in breast cancer prognosis and resistance to therapy. The proposed project will also provide a foundation for my future as a Physician Scientist in the field of Oncology.