Deciphering Mechanisms by which Tumor Cells Collaborate to Mediate Metastasis

事实上，所有乳腺癌（BC）相关的死亡都是由转移性负担而不是原发性肿瘤引起的。它有 长期以来，人们一直认为原发性肿瘤是异质性的，只有一些细胞有能力 转移我们的工作表明，这种观点过于简单化，非转移性细胞可以变得更多， 转移是由于来自其他癌细胞的旁分泌介导的信号传导。了解这一机制将 发现抑制转移性疾病的新策略。 为了了解异质性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）Twist 1和Snail 1的转移细胞是否可以 促进本质上非转移性细胞的转移特性。我们的数据显示，在某种程度上， 在第三EMT TF Six 1上，EMT TF可以非细胞自主地增强转移特性。 从机制上讲，我们发现表达Six 1的细胞介导GLI介导的信号传导的旁分泌激活， 本质上非转移性细胞，导致这些细胞的侵袭性和转移增加。重要的是， 旁分泌介导的GLI激活可通过非经典途径发生，不依赖于Hedgehog（Hh） 配体和Smoothened（SMO）介导的Hedgehog信号传导。 我们强大的数据使我们假设，SMO抑制剂，这是在临床试验中，将失败，在一个大的 BC患者的百分比。我们假设直接靶向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），以及决定分子水平的 非经典旁分泌GLI激活的机制将导致在广泛的免疫学和免疫学中有效的额外疗法。 BC的范围。此外，我们假设，使用我们的新型小分子靶向中心介体Six 1， 由于其在肿瘤中的细胞和非细胞自主作用， 进展为了验证这些相关的假设，我们将首先确定旁分泌机制， EMT/转移性细胞增加了本质上非转移性细胞的侵袭性，集中在VEGF-C和 其下游信号传导作为关键介质。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物（PDX）模型中EMT/转移性和非转移性细胞串扰的抑制剂 包括各种乳腺癌亚型和转移性，以确定哪些抑制剂是有效的 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。 我们的工作可以部分解释为什么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，我们不仅可以解释 这一领域的争议，但更重要的是，可能会确定高度有效的手段，以针对许多BC， 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.