A Bioengineered Model of Tumor Vessel Interactions in Pancreatic Cancer

胰腺导管腺癌（PDAC）是恶性肿瘤中导致癌症死亡的主要原因。PDAC是 高侵袭性，并在肿瘤进展的非常早期阶段在远处器官中形成转移。更好地 为了了解PDAC转移，需要进一步评估肿瘤-血管相互作用，因为肿瘤细胞 主要通过血液循环传播。然而，PDAC如何与血管相互作用并建立 对远处转移了解甚少。最近，我们的研究使用三维（3D）仿生 PDAC芯片和多种体内小鼠模型显示，PDAC细胞侵入血管， 通过ALK 7信号转导积极取代内皮细胞，导致肿瘤-血管杂交结构的形成。 PDAC肿瘤我们将这种现象称为肿瘤血管置换。尽管这一发现很新奇，但它 目前尚不清楚PDAC中肿瘤血管置换的生物学后果是什么。了解 肿瘤血管置换的表型结果对于确定临床相关性至关重要， 阻断PDAC中ALK 7的意义。我们假设PDAC肿瘤血管置换术增加了肿瘤 血管通透性;然后通过促进肿瘤细胞进入血管，促进肿瘤浸润和转移。 血液通过渗漏的血管循环。为了检验这些假设，我们的目标是确定-在这两个 体外和体内-（i）如果肿瘤血管置换诱导肿瘤血管渗漏并促进转移 如果ALK 7抑制或ALK 7敲除（KO）改善或逆转肿瘤血管渗漏 和转移。在目的1中，我们将评估ALK 7在周细胞覆盖的血液中PDAC血管通透性中的作用。 通过共培养微血管内皮细胞和周细胞以模拟生理血管的芯片上血管 被周细胞包围（Aim 1.1）。接下来，我们将评估ALK 7在体内PDAC血管功能障碍中的作用。 我们将使用野生型或ALK 7-KO PDAC细胞产生原位PDAC模型，并检查PDAC肿瘤 通过静脉内注射葡聚糖分子（Aim 1.2）测定血管通透性。在目标2中，我们将检查ALK 7， 通过在储库中建立转移前肝脏微环境， 与人造血管相连。将评估多个PDAC细胞系以测试ALK 7介导的PDAC细胞系是否与ALK 7介导的PDAC细胞系结合。 肿瘤血管置换影响转移扩散（目的2.1）。然后，我们将评估ALK 7在PDAC中的作用。 与Manuel Hidalgo博士合作，使用人类患者来源的异种移植物（PDX）模型进行体内转移。 将评估对照组与ALK 7 KO组中的转移性肿瘤负荷，并且将评估循环肿瘤的数量。 细胞和总存活率将被确定（目标2.2）。总之，我们的3D PDAC片上系统将提供 这是一个独特的平台，可以更好地研究PDAC与血管的相互作用和转移进展。我们将 解读ALK 7信号传导在介导肿瘤血管失调和转移中的作用;并评估 我们是否能够通过靶向ALK 7来减少PDAC进展和转移。

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer deaths among malignancies. PDAC is highly invasive and forms metastases in distant organs at the very early stage of tumor progression. To better understand PDAC metastasis, tumor-blood vessel interactions need to be evaluated further, as tumor cells spread primarily through the blood circulation. However, how PDAC interacts with blood vessels and establishes distant metastases are poorly understood. Recently, our study using both three-dimensional (3D) biomimetic PDAC-on-chip and multiple in vivo mouse models showed that PDAC cells invaded blood vasculatures and actively replaced endothelial cells via ALK7 signaling, leading to a formation of tumor-vessel hybrid structure in PDAC tumors. We refer to this phenomenon as tumor vessel replacement. Despite the novelty of the finding, it is unknown what the biological consequences of the tumor vessel replacement in PDAC are. Understanding the phenotypic consequences of the tumor vessel replacement is critical to determine the clinical relevance and significance of blocking ALK7 in PDAC. We hypothesize that PDAC tumor vessel replacement increases tumor vessel permeability; then promotes tumor intravasation and metastasis by facilitating tumor cells’ entering the blood circulation through the leakier vessels. In order to test these hypotheses, we aim to determine—in both in vitro and in vivo—(i) if tumor vessel replacement induces tumor vessel leakiness and promotes metastatic dissemination and (ii) if ALK7 inhibition or ALK7 knock out (KO) ameliorates or reverses tumor vessel leakiness and metastasis. In Aim 1, we will assess the role of ALK7 in PDAC vessel permeability in pericyte-covered blood vessel on-chip by co-culturing microvascular endothelial cells and pericytes to mimic physiological blood vessels surrounded by pericytes (Aim 1.1). Next, we will evaluate the role of ALK7 in PDAC vessel dysfunction in vivo. We will generate an orthotopic PDAC model using wild-type or ALK7-KO PDAC cells, and examine PDAC tumor vessel permeability by intravenously injecting dextran molecules (Aim 1.2). In Aim 2, we will examine ALK7 in PDAC metastasis in vitro by establishing pre-metastatic liver microenvironment in the reservoirs that are connected to the engineered blood vessel. Multiple PDAC lines will be assessed to test whether ALK7-mediated tumor vessel replacement affects metastatic spreading (Aim 2.1). We will then evaluate the role of ALK7 in PDAC metastasis in vivo using human patient-derived xenograft (PDX) models in collaboration with Dr. Manuel Hidalgo. Metastatic tumor burdens in control vs. ALK7 KO groups will be assessed, and the number of circulating tumor cells and overall survival rate will be determined (Aim 2.2). In summary, our 3D PDAC-on-chip system will provide a unique platform to better investigate PDAC interactions with blood vessels and metastatic progression. We will decipher the roles of ALK7 signaling in mediating tumor vessel dysregulation and metastasis; and assess whether we will be able to reduce PDAC progression and metastasis by targeting ALK7.