Novel immune suppressive activities of Fas/CD95 in triple negative breast cancer

总结 在女性中，乳腺癌（BC）是最常见的恶性肿瘤，也是第二大癌症原因 死亡基础/三阴性BC（TNBC）患者的临床结局最差， 与其他分子亚型相比，Fas/CD 95是一种良好表征的死亡 受体，当受其同源配体FasL刺激时，在允许细胞中介导凋亡的诱导。它 Fas也具有多种非凋亡的促肿瘤功能。高Fas 表达是TNBC的负预后因素。我们之前已经在多个基因组中证明了 具有组织特异性Fas缺失的工程化小鼠肿瘤模型，癌细胞保持Fas表达 没有Fas，肿瘤就不会生长。然而，一些肿瘤仍然在这些敲除（KO）小鼠中形成，这是由于 从Cre重组中逃脱。目前还不清楚Fas的这种活性是细胞自主的，还是 肿瘤微环境所需的细胞。关于TNBC小鼠模型的新的初步数据现在表明 肿瘤细胞表达Fas发挥免疫抑制活性，促进髓源性 抑制细胞（MDSC），导致自然杀伤（NK）细胞抑制肿瘤浸润。最近 我们发现，KPC 2，一种新的Fas相互作用伴侣，结合到C末端，在未受刺激的情况下， TNBC细胞隔离NF-κB亚基p65和KPC 1，KPC 1是一种降解p50的泛素连接酶 前体P105。我们发现，当Fas被清除时，p105被降解，改变了NF-κB的平衡， 从抑制性p50/p50同源二聚体到转录活性p50/p65异源二聚体。这反过来 释放大量促炎细胞因子的产生，这些细胞因子调节大量 免疫细胞包括NK细胞。基于这些初步数据，我们假设在TNBC中Fas作为一种免疫调节剂， NK细胞的新免疫检查点可能通过重塑免疫景观，即新的Fas结合 KPC 2周围的蛋白复合物负责Fas的免疫抑制活性， 破坏这种相互作用释放出可用于靶向TNBC细胞的抗肿瘤活性。这些 将在两个具体目标中研究假设：具体目标1：表征 Fas在三阴性乳腺癌中的应用。具体目标2：确定Fas表达如何抑制细胞凋亡， 促炎程序本项目的目标是表征Fas在促进TNBC中的新活性 生长和转移以及对NK细胞的免疫抑制作用。该项目将增加我们的 关于复杂和关键的受体/配体信号传导对在癌症中的作用的知识， 误会了直到最近，FasL的抑制（而不是其使用）才被认为是治疗癌症的有价值的选择。 在临床上治疗癌症在TNBC中，我们的工作现在指向抑制Fas受体， 其配体。最后，Fas新的免疫抑制活性为联合收割机 用常规检查点抑制剂抑制Fas/FasL用于治疗TNBC。

Summary Among women, breast cancer (BC) is the most common malignancy, and the second leading cause of cancer death. Patients with basal/triple negative BC (TNBC) have the poorest clinical outcome with no targeted therapies available when compared to other molecular subtypes. Fas/CD95 is a well characterized death receptor that in permissive cells mediates induction of apoptosis when stimulated by its cognate ligand, FasL. It is now well established that Fas also has multiple nonapoptotic, tumor promoting functions. High Fas expression is a negative prognostic factor for TNBC. We have previously demonstrated in multiple genetically engineered mouse tumor models with tissue specific deletion of Fas that cancer cells maintain Fas expression and without Fas tumors do not grow. However, some tumors still formed in these knock-out (KO) mice due to ‘escapers’ from Cre recombination. It remained unclear whether this activity of Fas was cell autonomous or required cells of the tumor microenvironment. New preliminary data on a mouse model of TNBC now suggest that tumor cell expressed Fas exerts an immune suppressive activity promoting recruitment of myeloid derived suppressor cells (MDSCs) resulting in inhibition of tumor infiltration by natural killer (NK) cells. Most recently we discovered, KPC2, a novel Fas interaction partner that binds to the C-terminal end and in unstimulated TNBC cells sequesters both the NF-κB subunit p65 and KPC1, a ubiquitin ligase that degrades the p50 precursor p105. We found that when Fas is eliminated p105 gets degraded shifting the balance of NF-κB subunits from repressive p50/p50 homodimers to transcriptionally active p50/p65 heterodimers. That in turn unleashes production of a number of proinflammatory cytokines that regulate the recruitment of a number of immune cells including NK cells. Based on these preliminary data we hypothesize that in TNBC Fas acts as a novel immune check point for NK cells likely by remodeling the immune landscape, that a novel Fas bound protein complex around KPC2 is responsible for this immune suppressive activity of Fas and finally, that disrupting this interaction unleashes an antitumor activity that can be used to target TNBC cells. These hypotheses will be studied in two specific aims: Specific Aim 1: Characterize immune suppressive activities of Fas in triple negative breast cancer. Specific Aim 2: To determine how Fas expression suppresses a proinflammatory program. The goal of this project is to characterize novel activities of Fas in promoting TNBC growth and metastasis as well as its immune suppressive function on NK cells. The project will increase our knowledge on the role of a complex and critical receptor/ligand signaling pair in cancer that has long been misunderstood. Only recently has inhibition of FasL (and not its use) been recognized as a valuable option for the treatment of cancer in the clinic. In TNBC our work now points at inhibiting the Fas receptor in addition to its ligand. Finally, the novel immune suppressive activity of Fas provides a compelling rationale to combine Fas/FasL inhibition with conventional checkpoint inhibitors for the treatment of TNBC.