Targeting posttranslational modifications of B7-H4 in carcinogenesis and therapy

靶向B7-H4翻译后修饰在肿瘤发生和治疗中的作用 这个项目的目标是确定B7-H4的糖基化和泛素化之间的相互作用的影响 在乳腺癌的发生和抗乳腺癌的治疗中。B7-H4，也称为含有T细胞的V-SET结构域 激活抑制因子1(VTCN1)是一种免疫检查点蛋白，其局部异常蓄积是 与包括三阴性乳腺癌(TNBC)在内的各种癌症的不良预后相关。而当 目前的一项TCGA研究表明，B7-H4在增加肿瘤对化疗药物的敏感性方面发挥了关键作用 和免疫检查点抑制剂，B7-H4是如何被调控的，以及它的放松对乳房的影响 癌症的发生和肿瘤药物的反应仍不清楚。我们最近对B7-H4进行纯化的结果 蛋白质复合体揭示了AMFR和STT3复合体这两种关键酶与其密切相互作用并进行调节 B7-H7。虽然E3泛素连接酶AMFR催化B7-H4的泛素化然后降解，但我们 观察到B7-H4蛋白被STT3复合体(一种糖基转移酶)糖基化导致 稳定B7-H4和抑制阿霉素诱导的免疫原性细胞死亡(ICD)B7-H4的标高 由于B7-H4糖基化增强导致的水平抵消了B7-H4泛素化，后者反过来抑制了 内质网应激介导的吞噬作用对化疗药物的反应，这是 通过ICD引发大规模肿瘤根除。我们进一步证明了通过阻断B7-H4糖基化 NGI-1是一种新的蛋白质糖基化抑制剂，显著增强B7-H4泛素化和随后的 降解，通过增加树突状细胞的吞噬作用和 它们能够激发产生CD8+干扰素γ的T细胞反应。在这个项目中，我们计划测试 假设通过糖基化和泛素化之间的串扰解除B7-H4的调控促进 肿瘤逃避化疗和NGI-1阻断B7-H4糖基化可能是一种新策略 用于抗TNBC治疗。为实现这一目标，我们提出了以下具体目标：(1)确定 糖基化和泛素化相互作用调节B7-H4的机制 吞噬作用；(2)确定STT3介导的糖基化和AMFR促进的生理相关性 B7-H4介导的ICD对化疗药物的泛素化反应；以及(3)确定临床 NGI-1阻断B7-H4糖基化在不同临床前小鼠抗肿瘤治疗中的相关性 模特们。

Targeting post-translational modifications of B7-H4 in carcinogenesis and therapy The goal of this project is to determine the impact of interplay between glycosylation and ubiquitination of B7-H4 in breast carcinogenesis and anti-breast cancer therapy. B7-H4, also known as V-set domain containing T cell activation inhibitor 1 (VTCN1), acts as an immune checkpoint protein whose local abnormal accumulation is correlated with poor prognosis of various types of cancers including triple negative breast cancer (TNBC). While a current TCGA study suggests the critical role of B7-H4 in conferring tumor sensitivity to chemotherapy drugs and immune checkpoint inhibitors, how B7-H4 is regulated and how its deregulation contributes to breast carcinogenesis and tumor drug response remain unknown. Results from our recent purification of the B7-H4 protein complex revealed that 2 critical enzymes, AMFR and STT3 complex, tightly interact with and regulate B7-H7. While the E3 ubiquitin ligase AMFR catalyzes ubiquitination of B7-H4 followed by degradation, we observed that glycosylation of B7-H4 protein by the STT3 complex (a glycosyltransferase) results in the stabilization of B7-H4 and inhibition of doxorubicin-induced immunogenic cell death (ICD). Elevation of B7-H4 levels due to enhanced B7-H4 glycosylation counteracts B7-H4 ubiquitination, which in turn suppresses endoplasmic reticulum stress-mediated phagocytosis in response to chemotherapy drugs, a critical step in triggering mass tumor eradication by ICD. We further demonstrated that blockade of B7-H4 glycosylation by NGI-1, a novel protein glycosylation inhibitor, significantly enhances B7-H4 ubiquitination and subsequent degradation, resulting in promotion of tumor killing efficacy due to increased phagocytosis by dendritic cells and their capacity to elicit CD8+ interferon-γ-producing T cell responses. In this project, we plan to test the hypothesis that deregulation of B7-H4 by the crosstalk between glycosylation and ubiquitination promotes TNBC tumor evasion from chemotherapy and blockade of B7-H4 glycosylation by NGI-1 could be a new strategy for anti-TNBC treatment. We propose the following specific aims to pursue this goal: (1) to determine the mechanism by which interplay between glycosylation and ubiquitination regulates B7-H4-orchestrated phagocytosis; (2) to determine the physiological relevance of STT3-mediated glycosylation and AMFR-facilitated ubiquitination in B7-H4-mediated ICD in response to chemotherapy drugs; and (3) to determine the clinical relevance of blockade of B7-H4 glycosylation by NGI-1 in anti-TNBC treatment using various preclinical murine models.