Deciphering Mechanisms by which Tumor Cells Collaborate to Mediate Metastasis

事实上，所有乳腺癌 (BC) 相关死亡都是由转移负担而非原发肿瘤造成的。它有 长期以来，人们一直认为原发性肿瘤是异质的，只有某些细胞有能力 转移。我们的工作表明这种观点过于简单化，并且非转移细胞可以变得更加简单。 由于来自其他癌细胞的旁分泌介导的信号传导而发生转移。了解这个机制将 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，我们检查了 表达 EMT 诱导转录因子 (TF)、Twist1 和 Snail1 的转移细胞是否可以 促进本质上非转移细胞的转移特性。我们的数据表明，以某种方式依赖 在第三个 EMT TF Six1 上，EMT TF 可以非细胞自主增强转移特性。 从机制上讲，我们发现表达 Six1 的细胞介导 GLI 介导的信号传导的旁分泌激活 本质上是非转移性细胞，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 激活可以通过独立于 Hedgehog 的非规范途径发生 (Hh) 配体和平滑 (SMO) 介导的 Hedgehog 信号传导。 我们强有力的数据使我们推测，正在进行临床试验的 SMO 抑制剂将在大规模试验中失败。 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（包括显示 EMT 特征的亚型），并确定分子 非典型旁分泌 GLI 激活机制将导致在广泛范围内有效的其他疗法 BC 的范围。此外，我们假设使用我们的新型小分子靶向中央介质 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 BC 中有效 进展。为了检验这些相关假设，我们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 VEGF-C 和 其下游信号作为关键调解者。然后我们将进行大规模的头对头比较 乳腺患者来源的异种移植 (PDX) 模型中 EMT/转移性和非转移性细胞串扰的抑制剂 涵盖各种乳腺癌亚型并且具有转移性，以确定哪些抑制剂是有效的 在更广泛的肿瘤中进行研究，并表征对特定抑制剂产生反应的肿瘤类型。 我们的工作可能部分解释了为什么 SMO 抑制剂作为单一药物在治疗中无效。 肿瘤，如 BC。此外，通过揭示 EMT 促进转移的新机制， 破译该机制的分子组成部分，我们不仅可以为该机制提供解释 该领域存在争议，但更重要的是确定针对许多 BC 的高效方法 其中一定比例的细胞经历了 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.