Divergent Roles of MerTK,Tyro3, and Axl in Pancreatic Cancer and Metastasis

摘要 胰腺导管腺癌（PDAC）可能是人类最易发生的肿瘤。总体占10% 5-年生存率和不断增加的发病率，PDAC将成为癌症死亡的第二大原因。 十年耐化疗和靶向治疗的肿瘤细胞群和肿瘤微环境 以抑制性先天免疫细胞和成纤维细胞为特征阻碍了治疗的成功。PDAC和临床前 PDAC模型均显示大量骨髓和成纤维细胞浸润，从而抑制效应T细胞， 促进转移。我们的数据涉及受体酪氨酸激酶Tyro 3，Axl，MerTK（TAM RTK）家族。 指导PDAC中CAF和骨髓细胞的促肿瘤极化。骨髓细胞的稳态作用 细胞TAM RTKs是协调对凋亡物质的先天免疫炎症反应的抑制 预防慢性炎症和自身免疫。我们的初步数据显示，TAM RTK发挥非- PDAC肿瘤微环境（TME）中的冗余和有时相反的功能，导致 骨髓细胞和成纤维细胞的极化。TAM RTK抑制的临床试验正在开始;因此，我们的工作， 因此，了解每种TAM RTK抑制的后果和机制是及时而有意义的。 野生型小鼠中的宿主MerTK和Tyro 3促进PDAC生长，并导致缺乏对抗PDAC抗体的反应性。 PD 1治疗，由于种系MerTK或Tyro 3缺失减缓PDAC生长，显著减少肝转移， 促进抗PD-1功效。然而，在Axl-/-小鼠中，转移性癌细胞的数量意外增加。 结果我们的团队已经合成了口服生物可利用的选择性MerTK激酶抑制剂， MerTK和/或Tyro 3遗传缺失的方面。最后，我们在患者中的初步研究确定了MerTK+和Tyro 3 + 骨髓细胞中，并记录PDAC患者血液中MerTK+/Tyro 3 + MDSC的增加。 假说. MerTK+和/或Tyro 3+单核细胞、巨噬细胞、MDSC和Tyro 3+成纤维细胞在培养皿中扩增。 PDAC，并且在抑制性TME和转移促进中具有至少一些单独的作用。我们的具体 目的1：确定MerTK和Tyro 3如何在先天免疫区室中起作用，以加速 PDAC的生长和转移以及Axl如何具有相反的作用。目的2：确定Tyro 3在以下中的作用： PDAC癌相关成纤维细胞和目的3：评估靶向TAM RTK在PDAC癌相关成纤维细胞中的治疗潜力。 临床前PDAC模型中的PDAC（使用PDAC抑制剂，其中一种处于I期试验中）与 其他细胞毒性和免疫疗法。我们将量化，功能特性，并研究基因表达 MerTK+和Tyro 3+髓样细胞在循环、肿瘤和淋巴结中的特征以及成纤维细胞在 PDAC患者在治疗前和治疗期间的肿瘤。如果成功， 了解如何使免疫学上“冷”的PDAC肿瘤“热”并对免疫疗法有反应。

ABSTRACT Pancreatic Ductal Adenocarcinoma (PDAC) is perhaps the most recalcitrant human neoplasm. With 10% overall 5-year survival and an increasing incidence, PDAC will be the second leading cause of cancer deaths within a decade. The constellation of chemo- and targeted therapy resistant tumor cells, and a tumor microenvironment featuring suppressive innate immune cells and fibroblasts frustrates therapeutic success. PDAC and preclinical PDAC models both show a massive myeloid and fibroblast cell infiltration which suppresses effector T cells and promotes metastases. Our data implicate a family of receptor tyrosine kinases Tyro3, Axl, MerTK (TAM RTKs) in directing pro-tumorigenic polarization of CAFs and myeloid cells in PDAC. The homeostatic role of myeloid cell TAM RTKs is to coordinate suppression of innate immune inflammatory responses to apoptotic material preventing chronic inflammation and autoimmunity. Our preliminary data, show that TAM RTKs play non- redundant and sometimes opposing functions in the PDAC tumor microenvironment (TME), leading to polarization of myeloid cells and fibroblasts. Clinical trials of TAM RTK inhibition are beginning; thus, our work to understand the consequences and mechanism of inhibition for each TAM RTK is both timely and significant. Host MerTK and Tyro3 in wild type mice promote PDAC growth and contribute to lack of responsiveness to anti- PD1 therapy, as germline MerTK or Tyro3 deletion slow PDAC growth, markedly reduces liver metastasis, and promotes anti-PD-1 efficacy. However, in the Axl-/- mice there is an unexpected increase in metastatic outgrowth. Our group has synthesized orally bioavailable, selective MerTK kinase inhibitors, which recapitulate aspects of MerTK and/or Tyro3 genetic loss. Lastly our preliminary studies in patients identify MerTK+ and Tyro3+ myeloid cells and document an increase in MerTK+/Tyro3+ MDSCs in the blood of PDAC patients. Hypothesis. MerTK+ and/or Tyro3+ monocytes, macrophages, MDSCs, and Tyro3+ fibroblasts are expanded in PDAC, and have at least some separate roles in the suppressive TME and metastasis promotion. Our Specific Aims are: Aim 1: To determine how MerTK and Tyro3 act in the innate immune compartment to accelerate PDAC growth and metastasis and how Axl has the opposite effect. Aim 2: To determine the role of Tyro3 in PDAC cancer associated fibroblasts and Aim 3: To evaluate the therapeutic potential of targeting TAM RTKs in PDAC in preclinical PDAC models (using UNC inhibitors one of which is in Phase 1 trials) in combination with other cytotoxic and immune therapies. We will quantify, functionally characterize, and study gene expression signature of MerTK+ and Tyro3+ myeloid cells in the circulation, tumors and lymph nodes and fibroblast cells in the PDAC patient tumors before and during therapy. Success would represent a significant advance toward understanding how to make immunologically “cold” PDAC tumors “hot” and responsive to immunotherapy.