Analyzes of the impact of GAS6/AXL signaling on hypoxia-induced metastasis and its therapeutic potential for the treatment of advanced hepatocellular carcinoma

肝细胞癌（HCC）是最常见的肝癌类型，是全球最致命的癌症之一。早期诊断是罕见的，由于治疗选择有限，晚期疾病的5年总生存率不到5%。HCC患者通常因转移而死亡。因此，了解肿瘤进展和转移的潜在机制是确定新的治疗靶点以改善患者预后的基础。GAS 6/AXL信号传导最近已成为多种癌症的引人注目的治疗靶点。在HCC中，受体酪氨酸激酶AXL的过度表达与晚期疾病阶段和较差的总生存率相关。HCC中特有的低氧张力，即所谓的缺氧，促进肿瘤的进展和转移，并显著诱导AXL的表达。然而，GAS 6/AXL信号传导对缺氧诱导的HCC进展和转移的影响知之甚少。在这个项目中，我将阐明GAS 6/AXL信号在缺氧诱导的肝癌转移的初始步骤中的作用，如上皮-间质转化和侵袭以及体内转移。此外，我将研究AXL信号阻断对干扰转移级联的治疗潜力。为了实现这些目标，我将利用遗传学方法沉默肝癌细胞系中的AXL，以评估AXL的生理作用和高亲和力可溶性AXL诱饵受体，以评估AXL抑制的治疗潜力。可溶性AXL诱饵受体先前是在我的宿主实验室中开发的，并且与野生型受体AXL相比，对GAS 6表现出显著更高的结合亲和力。使用AXL抑制剂处理的AXL沉默HCC细胞系或野生型HCC细胞系，我将分析缺氧诱导的上皮-间质转化、侵袭以及异种移植物和同基因同种异体移植物中原发性和转移性HCC生长的变化。使用转移模型，我将定义治疗性AXL抑制对减少已经存在的转移的影响，并将其疗效与标准治疗索拉非尼进行比较。这具有很高的临床意义，因为晚期HCC患者在诊断时通常携带转移灶。拟议项目的成功完成将为支持使用AXL抑制剂治疗晚期转移性HCC提供临床前数据。该项目具有高度的临床相关性，因为迫切需要晚期HCC的新治疗选择。

Hepatocellular carcinoma (HCC), the most common type of liver cancer, is one of the most lethal cancers worldwide. Early diagnosis is rare, and advanced disease stages show a 5-year overall survival of less than 5% due to limited treatment options. HCC patients typically die due to their metastases. Hence, understanding the underlying mechanisms of tumor progression and metastasis are fundamental to identify new therapeutic targets to improve patient outcome. GAS6/AXL signaling has recently emerged as a compelling therapeutic target for multiple cancers. In HCC, the overexpression of AXL, a receptor tyrosine kinase, is associated with advanced disease stages and poor overall survival. Characteristic low oxygen tensions in HCC, so called hypoxia, promote tumor progression and metastasis and notably induce the expression of AXL. However, the impact of GAS6/AXL signaling on hypoxia-induced HCC progression and metastasis are poorly understood. In the proposed project, I will clarify the role of GAS6/AXL signaling in the hypoxia-induced initial steps of HCC metastasis such as epithelial-mesenchymal transition and invasion as well as in metastasis in vivo. Moreover, I will examine the therapeutic potential of AXL signaling blockade on interfering with the metastatic cascade. To achieve these goals, I will utilize genetic approaches to silence AXL in HCC cell lines to assess the physiological role of AXL and a high affinity soluble AXL decoy receptor to assess the therapeutic potential of AXL inhibition. The soluble AXL decoy receptor was previously developed in my host laboratory and exhibits substantially higher binding affinity to GAS6 than to the wildtype receptor AXL. Using the AXL-silenced HCC cell lines or wildtype HCC cell lines treated with the AXL inhibitor, I will analyze changes in hypoxia-induced epithelial-mesenchymal transition, invasion, and primary and metastatic HCC growth in xenografts and syngeneic allografts. Using metastasis models, I will define the impact of therapeutic AXL inhibition on the reduction of already existing metastases, and compare its efficacy with the standard of care treatment sorafenib. This is of high clinical relevance, since advanced HCC patients commonly carry metastases at the time of their diagnosis.The successful completion of the proposed project will provide preclinical data to support the use of AXL inhibitors for the treatment of advanced, metastatic HCC. This project is of high clinical relevance, since new treatment options for advanced HCC are urgently needed.