Role of inflammation and microRNA network in brain metastasis of breast cancer

 描述（由申请人提供）：摘要大约20-30%的转移性乳腺癌患者发生脑转移，这几乎总是致命的，这些患者的中位生存时间只有几个月。这一观察结果对于三阴性肿瘤患者尤其紧迫。具有讽刺意味的是，化疗的最新进展进一步增加了脑转移的发病率，因为大多数治疗剂不能有效地穿透血脑屏障，肿瘤细胞发现大脑是一个避难所。因此，阐明转移过程中涉及的分子机制以确定特定的治疗靶点至关重要。最近的癌症干细胞理论预测，转移起始细胞（MIC）被定义为癌症干细胞样细胞（CSC）。然而，中等收入国家如何适应自己或被动地在大脑中产生利基是一个关键问题。我们最近发现，（i）脑MIC高度表达激活星形胶质细胞的关键炎性细胞因子IL-1β，（ii）分泌的IL-1β上调再激活的星形胶质细胞中的Notch配体Jagged 1，其进而激活MIC中的Notch信号传导，（iii）IL-1β还动员microRNA， （iv）miR 301和miR 629作为外来体从癌细胞分泌并抑制VHL表达，这导致星形胶质细胞中的HIF-1和VEGF-D活化，以及（v）VEGF-D然后促进MIC自我更新。基于这些初步数据，我们假设脑MIC分泌IL-1β，其上调星形胶质细胞中的Notch配体表达，并且还刺激肿瘤细胞释放外泌体miR 301/miR 629，其一起激活癌症相关星形胶质细胞，从而促进MIC自我更新。我们还假设分泌的外泌体可以在早期阶段作为脑转移的生物标志物，并且BBB可渗透和热活化的前药可以通过阻断IL-1β和Notch信号传导来抑制脑转移进展。为了验证这些假设，我们将首先阐明外泌体microRNA在脑中转移性小生境产生中的作用（目的1）。我们还将确定IL 1 β介导的microRNA网络激活和Notch通路在脑转移中MIC自我更新中的作用（目的2）。然后，我们将检查BBB可渗透和热活化的前药对脑转移的功效（目的3）。我们的研究是高度创新的，因为（i）我们已经确定了大脑微环境，特别是星形胶质细胞，在MIC自我更新的进展中的关键作用，（ii）我们表明IL-1β也促进外泌体microRNA的分泌，（miR 301/miR 629），其在干细胞龛中充当细胞间通讯的信使，（iii）我们将探索这些外泌体microRNA是否可以用作脑转移早期诊断的生物标志物，（iv）我们将开发一种创新的IL 1 RA前药，以靶向脑中的肿瘤细胞和微环境细胞。我们相信，我们的研究结果将为我们目前对脑转移病理学的理解提供一个范式转变，并对脑转移的早期检测以及这种毁灭性疾病的未来治疗产生重大影响。

 DESCRIPTION (provided by applicant): Summary Approximately 20-30% of patients with metastatic breast cancer develop brain metastasis, which is almost always fatal, and the median survival time of these patients is only few months. This observation is particularly imminent for patients with triple negative tumors. Ironically, recent advancement in chemotherapy has further increased the incidence of brain metastasis because most therapeutic agents cannot effectively penetrate the BBB and tumor cells find the brain as a sanctuary. Therefore, it is of paramount importance to elucidate the molecular mechanism involved in the metastatic process in order to define a specific therapeutic target. The recent cancer stem cell theory predicts that metastasis initiating cells (MIC) are by definition cancer stem-like cells (CSC). However, how MICs adapt themselves or passively generate a niche in the brain is a critical question. We have recently found that (i) brain MICs highly express the key inflammatory cytokine, IL-1β, which activates astrocytes, (ii) the secreted IL-1β up-regulates Jagged1, a Notch ligand, in the reactivated astrocytes, which in turn activates Notch signaling in MICs, (iii) IL-1β also mobilizes a microRNA network by activating miR301 and miR629, (iv) miR301 and miR629 are secreted from cancer cells as exosomes and suppress VHL expression, which results in HIF-1 and VEGF-D activation in astrocytes, and (v) VEGF-D then promotes MIC self-renewal. Based on these preliminary data, we hypothesize that brain MICs secrete IL-1β, which up-regulates Notch ligand expression in astrocytes and also stimulates the release of exosomal miR301/miR629 from the tumor cells that together activate cancer associated astrocytes, thereby, promoting MIC self-renewal. We also hypothesize that the secreted exosomes can serve as biomarkers for brain metastasis at an early stage and that a BBB-permeable and thermo-activatable pro-drugs can suppress brain metastasis progression by blocking IL-1β and Notch signaling. To test these hypotheses, we will first elucidate the roles of exosomal microRNAs in the metastatic niche generation in the brain (Aim 1). We will also define the role of IL1β-mediated activation of a microRNA network and Notch pathway in self-renewal of MICs in brain metastasis (Aim 2). We will then examine the efficacy of a BBB-permeable and thermo-activatable pro-drug on brain metastasis (Aim 3). Our study is highly innovative in that (i) we have identified the critical role of the brain microenvironment, particularly astrocytes, in the progression of MIC self- renewal, (ii) we showed that IL-1β also promote the secretion of exosomal microRNAs (miR301/miR629), which act as messengers for cell-cell communications in the stem cell niche, (iii) we will explore whether these exosomal microRNAs can be used as biomarkers for early diagnosis of brain metastasis, (iv) we will develop an innovative IL1RA pro-drug to target both tumor and microenvironmental cells in the brain. We believe that the outcome of our study will provide a paradigm shift in our current understanding of the pathology of brain metastasis and also have a significant impact on early detection of brain metastasis as well as on future treatments for this devastating disease.