Osteoclast-independent mechanisms of early-stage bone colonization of breast canc

项目摘要 几乎所有的乳腺癌相关死亡都是由转移引起的。骨骼是最常受影响的器官， 乳腺癌在有临床意义的阶段，骨转移是由恶性循环之间的癌症 细胞和破骨细胞（骨吸收细胞）。近年来，我们对这种恶性循环的了解大大增加。 年，靶向破骨细胞的治疗通常可以显着延缓疾病的进展。然而，在这方面， 骨转移仍然无法治愈。另一方面，通常有几年到几十年的潜伏期， 骨转移变得临床可检测，表明残余癌细胞可存在于骨或骨中。 骨髓中的一个延长的一段时间，而不激活破骨细胞。我们开始探索破骨细胞- 在恶性循环开始之前的早期骨定植的独立机制。我们的预- 没有数据表明成骨细胞（造骨细胞）及其前体细胞构成微环境， 显微镜下骨转移瘤的边缘龛。癌细胞和“骨- “teoblastic niche”对它们的增殖至关重要。进一步的研究表明，mTOR的重新激活 是骨转移起始的标志。我们还获得了初步证据，表明 mTOR的激活是由癌细胞和小生境之间的粘附连接（AJs）的形成介导的 细胞基于这些发现，我们假设成骨细胞龛促进骨转移进展- 通过增强mTOR活性将乳腺癌从单细胞锡永到多细胞微转移 途径，可能通过AJ复合物的下游信号传导。为了验证这一假设，我们将追踪两个 具体目的：1）确定介导癌细胞和骨之间串扰的机制， 母细胞龛，这需要直接的细胞-细胞接触，并导致mTOR信号转导的激活，和2）识别， 激活mTOR的下游效应子，驱动转移起始。我们的工作具有创新性和可行性- 因为它采用了一种新的技术，通过血液循环选择性地将癌细胞输送到后肢骨骼中。 这种方法能够在单细胞分辨率下快速检查和稳健定量骨微转移， 解决方案，但避免了其他传统方法的警告。该技术在几种癌症中的应用 模型导致模拟人类疾病的惰性或休眠骨转移。我们将使用这个AP- 分别用于人类和小鼠癌细胞的异种移植和同基因移植的方法，并研究 拮抗AJs、mTOR复合物及其相关信号分子在骨转移起始阶段的作用， 是的。此外，我们还发明了一种3D共培养系统，忠实地再现了癌症的许多特征- 生态位相互作用，这将有助于解剖分子机制，加快我们的检查 候选调解人。这些目标的实现将使靶向治疗的设计能够抑制或 根除潜伏的肿瘤细胞，并降低明显的骨转移相关症状的发生率和死亡率。

Project Summary Metastasis accounts for nearly all breast cancer-related deaths. Bone is the organ most frequently affected by breast cancer. In the clinically significant stage, bone metastasis is driven by a vicious cycle between cancer cells and osteoclasts (bone-resorbing cells). Our knowledge of this vicious cycle has vastly increased in recent years, and therapies targeting osteoclasts can often significantly delay the progression of disease. However, bone metastases still remain incurable. On the other hand, there is often a latency of years to decades before bone metastases become clinically detectable, suggesting that residual cancer cells can exist in bone or bone marrow for a protracted period of time without activating osteoclasts. We set out to discover osteoclast- independent mechanisms in early-stage bone colonization before the onset of the vicious cycle. Our prelimi- nary data demonstrated that osteoblasts (bone-making cells) and their precursor cells constitute the microenvi- ronment niche of microscopic bone metastases. The direct cell-cell contact between cancer cells and the "os- teoblastic niche" is crucial for their proliferation. Further studies indicated that the re-activation of the mTOR pathway is a hallmark of bone metastasis initiation. We also obtained preliminary evidence suggesting that the activation of mTOR is mediated by the formation of adhesion junctions (AJs) between cancer cells and niche cells. Based on these findings, we hypothesize that the osteoblastic niche facilitates bone metastasis progres- sion of breast cancer from single cells to multi-cell micrometastases by augmenting the activity of the mTOR pathway, possibly through signaling downstream of AJ complexes. To test this hypothesis, we will pursue two specific aims: 1) to determine the mechanism mediating the crosstalk between cancer cells and the osteo- blastic niche, which entails direct cell-cell contact and leads to the activation of mTOR signaling, and 2) to iden- tify the downstream effectors of mTOR that drive metastasis initiation. Our work is innovative and feasible be- cause it employs a novel technique that selectively delivers cancer cells into hind limb bones via the circulation. This approach enables swift inspection and robust quantification of bone micrometastases at a single-cell reso- lution, yet avoids caveats of other conventional approaches. Application of this technique to several cancer models resulted in indolent or dormant bone metastases that mimic human diseases. We will use this ap- proach for xenograft and syngeneic transplantation of human and mouse cancer cells, respectively, and inves- tigate the roles of AJs, the mTOR complexes, and their related signaling molecules in bone metastasis initia- tion. In addition, we also invented a 3D co-culture system that faithfully recapitulates many features of cancer- niche interaction, which will facilitate the dissection of molecular mechanisms and accelerate our examination of candidate mediators. The fulfillment of these aims will enable the design of targeted therapies to suppress or eradicate latent tumor cells, and reduce the incidence of overt bone metastasis-related symptoms and mortality.