The Potential Role of Firboblast Activation Protein as a Natural Killer Cell Immune Checkpoint in Pancreatic Cancer

项目摘要 免疫治疗在胰腺癌中基本无效，部分原因是周围致密的间质 纤维化，其产生免疫抑制微环境。纤维化的主要细胞成分， 胰腺星状细胞（PSC）以成纤维细胞活化蛋白（FAP）表达升高为标志。FAP 是一种II型跨膜丝氨酸蛋白酶，在正常胰腺中表达最低，然而， 胰腺癌FAP在90%的病变中过表达，并且与更差的临床结果相关。这里 我们使用了一种新的体外共培养系统，该系统利用了原代供体来源的PSC和人类自然杀伤细胞， (NK)细胞系NK 92，以评估PSC和NK细胞之间的关系。我们测试了NK细胞的能力， 杀死PSC并监测FAP表达和活化标志物。我们还评估了FAP的作用 体外NK细胞活性抑制和体内胰腺肿瘤清除。我们发现NK细胞被激活 可能通过NK细胞表面受体NKG 2D识别PSCs上的云母/B。在直接 与PSC接触，PSC下调FAP，而NK细胞上调FAP。这是第一次NK细胞 已经显示产生FAP，并且FAP的诱导是由细胞与细胞接触介导的。此外，委员会认为， NK细胞的FAP表达与NK细胞表型相关。FAP抑制增强NK杀伤， PSC在体外和增强胰腺肿瘤清除在体内。FAP抑制剂的抗肿瘤活性是 通过添加抗PD-1治疗增强。基于这些发现，我假设FAP作为NK功能 细胞免疫检查点FAP在活化后在NK细胞中表达以减弱细胞毒性，并且可以在NK细胞中表达。 抑制以增强抗肿瘤免疫。为了验证这一假设，我的目标是确定FAP的机制， NK细胞诱导（目的1），评估这些发现的临床相关性（目的1A和1D），并操作 增强体外和体内抗肿瘤免疫应答的FAP活性（目的2）。成功完成 这些目标将确定调控FAP表达的因素，并进一步了解FAP如何调控 免疫反应。这些发现将填补围绕FAP表达调节因子的知识的差距 为增强抗肿瘤免疫活性提供了新的途径。

PROJECT SUMMARY Immunotherapy has been largely ineffective in pancreatic cancer, partially due to the surrounding dense stromal fibrosis which creates an immunosuppressive microenvironment. The main cellular component of this fibrosis, pancreatic stellate cells (PSCs), are marked by elevated expression of fibroblast activation protein (FAP). FAP is a type II transmembrane serine protease that is minimally expressed in normal pancreas, however, in pancreatic cancer FAP is overexpressed in 90% of lesions and is associated with worse clinical outcomes. Here we use a novel in vitro co-culturing system that utilizes primary donor-derived PSCs and a human natural killer (NK) cell line, NK92, to assess the relationship between PSCs and NK cells. We tested the ability of NK cells to kill PSCs and monitored for FAP expression and markers of activation. We also assessed the effect of FAP inhibition on NK cell activity in vitro and pancreatic tumor clearance in vivo. We found that NK cells are activated by and kill PSCs, potentially via NK cell surface receptor NKG2D recognition of MICA/B on PSCs. Upon direct contact with PSCs, PSCs downregulate FAP, however, NK cells upregulate FAP. This is the first-time NK cells have been shown to produce FAP and that induction of FAP is mediated by cell-to-cell contact. Furthermore, FAP expression by NK cells is associated with an inactivate phenotype. FAP inhibition enhanced NK killing of PSCs in vitro and enhanced pancreatic tumor clearance in vivo. The anti-tumor activity of FAP inhibition was enhanced by addition of anti-PD-1 therapy. Based on these findings, I hypothesize that FAP functions as an NK cell immune checkpoint. FAP is expressed in NK cells after activation to attenuate cytotoxicity and can be inhibited to enhance anti-tumor immunity. To test this hypothesis, I aim to determine mechanisms of FAP induction in NK cells (Aim 1), assess the clinical relevance of these findings (Aim 1A and 1D) and manipulate FAP activity to enhance in vitro and in vivo anti-tumor immune responses (Aim 2). Successful completion of these aims will identify factors that regulate FAP expression and further our understanding of how FAP regulates the immune response. These findings will fill the gap in knowledge surrounding regulators of FAP expression and provide new approaches to enhance anti-tumor immune activity.