Ceramide metabolism and the regulation of PD-L1 signaling to control metastasis and resistance to immunotherapy in TNBC

摘要 转移是三阴性乳腺癌(TNBC)患者死亡的一个重要原因，中位数为 总体生存时间不到一年。免疫疗法的引入彻底改变了系统性 转移性癌症的治疗。然而，有一些潜在的抗性机制限制了对 TNBCs的免疫治疗。PD-L1细胞表面表达增加与对α-1的反应增强有关 PD-L1或α-PD-1疗法。肿瘤细胞对免疫治疗产生抵抗力的一个潜在机制 是通过减少细胞膜上PD-L1的表达。此外，最近的报告表明， 内化(非膜性)PD-L1参与癌细胞内的致癌/促转移信号 没有太多机械性的理解。已知脂代谢和信号变化在其中起一定作用。 在癌细胞迁移/侵袭和肿瘤转移中的作用，包括生物活性神经鞘脂神经酰胺的减少 介导促凋亡和抗增殖的信号转导。我们最近发现神经酰胺的减少 合成酶4(CerS4)产生的长链C18-C20神经酰胺通过以下途径诱导TNBC迁移和转移 激活转化生长因子-β/Sonic Hedgehog(Shh)信号轴。然而，这其中的监管部分 机制仍不清楚。基于我们已发布和未发布的初步数据，此应用程序是 旨在测试一个新的总体假设，即CerS4产生的神经酰胺信号的减少增强了 PD-L1内化，诱导促转移信号并促进免疫治疗抵抗 TNBC。提出了两个具体目标：目标1旨在定义减少 CerS4/神经酰胺信号调节PD-L1内化及其细胞内转移信号。目标2是 旨在确定CerS4/神经酰胺信号如何调节PD-L1/Caprin-1复合体以控制TNBC 转移和对免疫治疗的抵抗。总体而言，本申请描述了一种新的抵抗机制 TO免疫治疗和脂质/神经酰胺驱动的细胞内PD-L1依赖的促转移信号 新陈代谢改变。针对这一信号网络的联合治疗可以减少转移 负担和改善转移性TNBC对免疫治疗的反应，共同解决临床未满足的问题 此应用程序中的需要。

SUMMARY Metastasis is a significant cause of mortality for patients with triple-negative breast cancer (TNBC), with a median overall survival of less than one year. The introduction of immunotherapy has revolutionized the systemic treatment of metastatic cancer. However, there are underlying resistance mechanisms that limit response to immunotherapy in TNBCs. Increased PD-L1 cell surface expression is associated with improved response to α- PD-L1 or α-PD-1 therapies. One potential mechanism by which tumor cells acquire resistance to immunotherapy is by reducing PD-L1 expression in the cell membrane. Furthermore, recent reports have demonstrated that internalized (non-membranous) PD-L1 participates in oncogenic/pro-metastatic signaling within cancer cells without much mechanistic understanding. It is known that lipid metabolism and signaling alterations play a role in cancer cell migration/invasion and tumor metastasis, including reductions of bioactive sphingolipid ceramide that mediates pro-apoptotic and anti-proliferative signaling. We recently showed that reductions in ceramide synthase 4 (CerS4)-generated long-chain C18-C20-ceramides induce TNBC migration and metastasis by activating the TGF-β/Sonic hedgehog (Shh) signaling axis. However, the regulatory components of this mechanism remain unknown. Based on our published and unpublished preliminary data, this application is designed to test a novel overall hypothesis that the reduction of CerS4-generated ceramide signaling enhances PD-L1 internalization, induces pro-metastatic signaling and facilitates resistance to immunotherapy in TNBC. There are two Specific Aims proposed: Aim 1 is designed to define the mechanism by which reduced CerS4/ceramide signaling regulates PD-L1 internalization and its intracellular metastatic signaling. Aim 2 is designed to determine how CerS4/ceramide signaling regulates the PD-L1/Caprin-1 complex to control TNBC metastasis and resistance to immunotherapy. Overall, this application describes a novel resistance mechanism to immunotherapy and intracellular PD-L1-dependent pro-metastatic signaling driven by lipid/ceramide metabolism alterations. Combination therapies targeting this signaling network could reduce the metastatic burden and improve metastatic TNBC response to immunotherapy, collectively addressing clinically unmet needs in this application.