Defining the Rules of Breast Cancer Cell Traffic Through Bone

摘要 乳腺癌死亡的主要原因是转移性复发，最常见的是首先发生在乳腺癌。 骨头对早期乳腺癌女性进行的骨髓（BM）活检表明， 许多患者在诊断时实际上存在小的、临床上不明显的“微转移”。 这些微转移瘤可以在辅助化疗中存活，并在化疗前潜伏多年。 它们变得增殖，引起明显的转移性疾病。在这个阶段，疾病变得无法治愈。 我们对乳腺癌生物学的日益了解向我们揭示了宿主的重要性 组织中创造一个接受和保护环境转移。我们实验室的初步数据 小鼠异种移植模型显示，乳腺癌细胞（BCC）转移到独特的 血管周围造血祖细胞和干细胞（HSPC）小生境。这些区域的血管 其特征在于它们的正弦形态和它们的粘附分子E-的高基础表达。 选择素和细胞因子SDF-1。使用高度特异性的E-选择素和CXCR 4抑制剂，我们已经确定， E-选择素和SDF-1在BCC贩运中协调相反的作用。虽然E-选择素相互作用对于 允许BCC进入BM，SDF-1/CXCR 4将BCC锚定到微环境，其抑制诱导 休眠的微转移进入循环的动员。此外，我们的免疫组织化学研究， 对微转移性骨髓受累患者进行的活检显示， 邻近SDF-1+脉管系统。基于这些数据，我们假设休眠的BCC庇护在 独特的窦周血管BM壁龛，它们能够动态地往返于 外周循环以及骨内替代的促增殖微环境。我们也 假设CXCR 4和E-选择素抑制等干预措施可以将休眠的BCC从细胞中清除， 保护性窦状隙，使他们容易受到细胞毒性或激素治疗。测试这些 假设，我们将使用单细胞分辨率，视频速率在体内显微镜在小鼠异种移植模型，以跟踪 BCC通过BM的真实的时间迁移。结合体外分子和细胞生物学方法， 我们将1）研究关键调节BCC转移进入骨的信号; 2）研究BCC转移进入骨的分子机制。 调节BCC从骨转移部位进入外周循环的机制以及 BCC信号传导和活力的动员;以及3）理解如何与窦周BM的串扰 血管生态位介导BCC休眠和对化学和激素疗法的敏感性。获得的知识 从这项工作将确定基本机制，管理动态运动的微转移 BCC，并将建议治疗方法，以靶向BM和休眠乳腺之间的支持性串扰 癌

ABSTRACT The major cause of death from breast cancer is metastatic relapse, which most commonly occurs first in the bone. Bone marrow (BM) biopsies performed on women with early stage breast cancer have shown that small, clinically unapparent “micrometastases” are actually present at the time of diagnosis in many patients. These micrometastases can survive in the face of adjuvant chemotherapy and lay dormant for years before they become proliferative, causing overt metastatic disease. At this stage, disease becomes incurable. Our increasing understanding of breast cancer biology has revealed to us the importance of the host tissue in creating a receptive and protective environment for metastases. Preliminary data from our lab using mouse xenograft models show that breast cancer cells (BCCs) metastasize to and lay dormant in unique perivascular hematopoietic progenitor and stem cell (HSPC) niches. The blood vessels in these regions are distinguished by their sinusoidal morphology and their high basal expression of the adhesion molecule E- selectin, and the cytokine SDF-1. Using highly specific E-selectin and CXCR4 inhibitors, we have identified that E-selectin and SDF-1 orchestrate opposing roles in BCC trafficking. While E-selectin interactions are critical for allowing BCC entry in BM, SDF-1/CXCR4 anchors BCCs to the microenvironment and its inhibition induces mobilization of dormant micrometastases into circulation. Moreover, our immunohistochemical studies of biopsies performed on patients with micrometastatic BM involvement show that dormant metastases reside adjacent to SDF-1+ vasculature. Based on these data, we hypothesize that dormant BCCs shelter within unique peri-sinusoidal vascular BM niches from which they are able to dynamically transit back-and-forth to the peripheral circulation as well as to alternative, pro-proliferative microenvironments within the bone. We also hypothesize that interventions such as CXCR4 and E-selectin inhibition can flush dormant BCCs from the protective sinusoidal niche, making them susceptible to cytotoxic or hormonal therapies. To test these hypotheses, we will use single cell resolution, video rate in vivo microscopy in mouse xenograft models to track BCC migration through BM in real time. In combination with in vitro molecular and cellular biology approaches, we will 1) Investigate the signals that critically regulate BCC metastatic entry in bone; 2) Study the molecular mechanisms that regulate BCC exit from bone metastatic sites into peripheral circulation and the impact of mobilization on BCC signaling and viability; and 3) Understand how cross talk with the peri-sinusoidal BM vascular niche mediates BCC dormancy and sensitivity to chemo- and hormonal therapies. Knowledge gained from this work will identify fundamental mechanisms governing the dynamic movement of micrometastatic BCCs and will suggest therapeutic methods to target supportive crosstalk between BM and dormant breast cancer.