Axl as a target for the therapy of pancreatic cancer

描述（由申请人提供）：胰腺导管腺癌（PDAC）中受体酪氨酸激酶Axl的表达升高与转移增加和生存期缩短相关。Axl通过肿瘤细胞存活，增殖， 耐药性、上皮向间质转化和肿瘤基质活化，包括血管生成和肿瘤相关巨噬细胞募集。Axl由单一配体激活，即维生素K依赖性γ-羧基谷氨酸（GLA）结构域蛋白Gas 6。异常激活可以通过非配体机制发生，包括相邻细胞上Axl胞外结构域之间的同型相互作用、与其他受体酪氨酸激酶和细胞质酪氨酸激酶（例如，Src家族）。Axl的抑制阻断了乳腺癌的转移活性并增强了药物敏感性，但在PDAC动物模型中靶向Axl的效果尚未评估。我们的初步研究证明，胰腺癌细胞中的Axl抑制减少了PI 3 K-Akt和MAP激酶信号传导，并大大降低了原位模型中的原发性和转移性负担。在本提案中，我们将扩大这些研究，并评估三种不同的策略，以消除Axl活性在体内的治疗效果。该提案的中心假设是靶向Axl将阻断PDAC进展并增强对标准治疗化疗的敏感性。我们将通过以下目的来解决这一假设：1）确定用临床维生素K依赖性羧化酶抑制剂华法林抑制Gas 6配体与Axl结合的治疗功效; 2）表征用新型治疗剂直接抑制Axl信号转导的抗肿瘤作用。我们已经证明，华法林可以降低Axl活性的剂量远低于抗凝活性所需的剂量。我们已经发现华法林以Axl依赖性方式在胰腺癌的原位模型中降低肿瘤负荷并阻断转移。我们将扩大这些研究，包括华法林在PDAC的本土模型中的疗效评价。与James Lorens教授实验室（卑尔根大学）合作，我们将探索一种新的抑制性抗Axl单克隆抗体10 C9和最近开发的口服小分子Axl受体酪氨酸激酶抑制剂（BGB 324）的疗效。将在胰腺癌的相关体内模型中测试用10 C9和BGB 324直接抑制Axl的治疗功效。我们的目标包括阻断Gas 6依赖性自分泌/旁分泌和非配体Axl激活。我们的总体目标是证明抑制Axl是治疗胰腺癌的可行治疗策略，并确定Axl抑制是否与当前治疗方式有效结合。

DESCRIPTION (provided by applicant): Elevated expression of the receptor tyrosine kinase Axl in pancreatic ductal adenocarcinoma (PDAC) is associated with increased metastasis and shorter survival. Axl participates in malignant progression via tumor cell survival, proliferation, drug resistance, epithelial-to-mesenchymal transition and tumor stromal activation including angiogenesis and tumor-associated macrophage recruitment. Axl is activated by a single ligand, the vitamin K-dependent gamma-carboxyglutamic (GLA) domain protein, Gas6. Aberrant activation can occur through non-ligand mechanisms including homotypic interaction between Axl extracellular domains on adjacent cells, crosstalk with other receptor tyrosine kinases and cytoplasmic tyrosine kinases (e.g., Src family). Inhibition of Axl blocks metastatic activity and enhances drug sensitivity in breast cancer, but the effect of targeting Axl in animal models of PDAC has not been evaluated. Our preliminary studies document that Axl inhibition in pancreatic cancer cells diminishes PI3K-Akt and MAP kinase signaling and strongly reduces primary and metastatic burden in orthotopic models. In the present proposal, we will expand on these studies and evaluate the therapeutic efficacy of three different strategies to abrogate Axl activity in vivo. The central hypothesis of the proposal is that targeting Axl will block PDAC progression and enhance sensitivity to standard-of-care chemotherapy. We will address this hypothesis with the following aims 1) to determine the therapeutic efficacy of inhibiting Gas6 ligand binding to Axl with the clinical vitamin K-dependent carboxylase inhibitor warfarin; 2) to characterize the anti-tumor effects of direct inhibition of Axl signal transduction with novel therapeutics. We have documented that warfarin can reduce Axl activity at doses much lower than those required for anticoagulant activity. We have found that warfarin reduces tumor burden and blocks metastasis in orthotopic models of pancreatic cancer in an Axl dependent manner. We will expand these studies to include evaluation of the efficacy of warfarin in autochthonous models of PDAC. In collaboration with Prof. James Lorens' laboratory (University of Bergen) we will explore the efficacy of a new inhibitory anti-Axl monoclonal antibody, 10C9 and a recently developed oral, small molecule Axl receptor tyrosine kinase inhibitor (BGB324). The therapeutic efficacy of direct Axl inhibition with 10C9 and BGB324 will be tested in relevant in vivo models of pancreatic cancer. Our aims encompass blockade of Gas6-dependent autocrine/paracrine and non-ligand Axl activation. Our overall goal is to document that inhibition of Axl is a viable therapeutic strategy for the treatment of pancreatic cancer and to determine if Axl inhibition combines effectively with current treatment modalities.