Deciphering Mechanisms by which Tumor Cells Collaborate to Mediate Metastasis

几乎所有与乳腺癌(BC)相关的死亡都是由转移负担造成的，而不是原发肿瘤。它有 长期以来，人们认为原发肿瘤是异质性的，只有一些细胞有能力 转移瘤。我们的工作表明，这种观点过于简单化，非转移性细胞可以变得更多 由于旁分泌介导的来自其他癌细胞的信号而转移。了解这一机制将 发现抑制转移性疾病的新策略。 为了了解异质肿瘤中不同转移潜能的细胞之间的串扰，我们研究了 表达EMT诱导转录因子Twist1和Snail1的转移细胞能否 促进本质上不转移的细胞的转移特性。我们的数据表明，在某种程度上， 在第三种EMT转移因子SIX1上，EMT转移因子可以非细胞自主地增强转移特性。 从机制上讲，我们证明了表达SIX1的细胞介导了GLI介导的信号的旁分泌激活 本质上不转移的细胞，导致这些细胞的侵袭性和转移性增加。重要的是 旁分泌介导的GLI激活可以通过不依赖Hedgehog(HH)的非规范途径发生。 配体和光滑(SMO)介导的Hedgehog信号转导。 我们强有力的数据让我们假设，处于临床试验中的SMO抑制剂将在很大程度上失败 BC患者的百分比。我们假设，直接针对GLI将在更广泛的范围内有效 乳腺肿瘤(包括表现出EMT特征的亚型)，以及决定分子 非典型旁分泌GLI激活的机制将导致在广泛有效的其他治疗 BCS的范围。此外，我们假设使用我们的新的小分子来靶向中心介体SIX1 抑制剂，由于其在肿瘤中的细胞和非细胞自主作用，将在最广泛的BCS范围内有效 进步。为了验证这些相关假设，我们将首先确定旁分泌机制， EMT/转移细胞增加本质上非转移细胞的侵袭性，重点是血管内皮生长因子-C和 它的下游信号是关键的介体。然后，我们将执行大规模的逐一比较 乳腺癌患者来源异种移植(PDX)模型中EMT/转移和非转移细胞串扰的抑制物 包括不同的乳腺癌亚型和转移性，以确定哪些抑制剂有效 在更广泛的肿瘤中，并描述对特定抑制剂有反应的肿瘤类型。 我们的工作可能为为什么SMO抑制剂作为单一药物无效提供了部分解释 BCS等肿瘤。此外，通过揭示EMT促进转移的新机制，以及通过 破译这一机制的分子成分，我们不仅可以解释 在该领域存在争议，但更重要的是，可能会找到针对许多BCS的高效手段 其中一定百分比的细胞已经经历了EMT。

Virtually all breast cancer (BC) related deaths result from metastatic burden rather than the primary tumor. It has long been thought that primary tumors are heterogeneous, with only some cells having the capacity to metastasize. Our work suggests that this view is oversimplified, and that non-metastatic cells can become more metastatic due to paracrine-mediated signaling from other cancer cells. Understanding this mechanism will uncover new strategies to inhibit metastatic disease. To understand crosstalk between cells of varying metastatic potential in heterogeneous tumors, we examined whether metastatic cells expressing the EMT-inducing transcription factors (TFs), Twist1 and Snail1, can promote metastatic properties in intrinsically non-metastatic cells. Our data show that, in a manner dependent on a third EMT TF, Six1, the EMT TFs can non-cell autonomously enhance metastatic properties. Mechanistically, we show that cells expressing Six1 mediate paracrine activation of GLI-mediated signaling in intrinsically non-metastatic cells, leading to increased aggressiveness and metastasis of these cells. Importantly, paracrine mediated activation of GLI can occur through non-canonical pathways independent of Hedgehog (Hh) ligands and Smoothened (SMO)-mediated Hedgehog signaling. Our strong data lead us to hypothesize that SMO inhibitors, which are in clinical trials, will fail in a large percentage of BC patients. We hypothesize that targeting GLI directly will be effective in a broader range of breast tumors (encompassing subtypes that show features of EMT), and that determining the molecular mechanism of non-canonical paracrine GLI activation will lead to additional therapies that are effective in a broad range of BCs. Further, we hypothesize that targeting the central mediator, Six1, using our novel small molecule inhibitor, will be efficacious in the broadest range of BCs due to its cell and non-cell autonomous role in tumor progression. To test these related hypotheses, we will first determine the paracrine mechanism by which EMT/metastatic cells increase the aggressiveness of intrinsically non-metastatic cells, focusing on VEGF-C and its downstream signaling as key mediators. We will then perform a large scale head-to-head comparison of inhibitors of EMT/metastatic and non-metastatic cell crosstalk in breast patient derived xenograft (PDX) models that encompass various breast cancer subtypes and are metastatic, to determine which inhibitors are efficacious in a broader range of tumors, and to characterize the types of tumors that will respond to specific inhibitors. Our work may provide a partial explanation for why SMO inhibitors have been ineffective as single agents in tumors such as BCs. Further, by uncovering a new mechanism by which EMT promotes metastasis, and by deciphering the molecular components of that mechanism, we may not only provide an explanation for the controversy in the field, but may more importantly identify highly efficacious means to target the many BCs in which a percentage of cells have undergone an EMT.