PKC agonism restricts innate immune suppression and promotes antigen cross-presentation in Triple Negative Breast Cancer

摘要 免疫检查点阻断(ICB)使癌症治疗发生了革命性的变化，呈现出前所未有的长期 抗肿瘤反应。然而，大多数患者对ICB疗法没有反应，至少部分原因是 免疫抑制。免疫治疗无效者循环中髓系衍生抑制物水平较高 细胞(MDSCs)-一种免疫抑制的先天细胞群体，既抑制先天细胞又抑制适应性细胞 豁免权。三阴性乳腺癌(TNBC)是乳腺癌中侵袭性最强的亚型。 对传统疗法的反应。TNBC患者的MDSC群体水平高于 非TNBC患者。因此，TNBC和其他血液循环水平较高的实体肿瘤患者 MDSCs对ICB的反应很差。因此，减少MDSC抑制功能同时促进MDSC的策略 CD8+T细胞的交叉激发很可能与ICB有效地结合起来，以获得最大的治疗益处。 蛋白激酶C(PKC)是一个由11个亚型组成的蛋白激酶家族，在细胞信号转导中发挥重要作用。 是髓系细胞中含量最丰富的亚型，在树突状细胞(DC)中起着重要作用。 功能。到目前为止，PKC在髓系细胞中的作用在癌症中的作用尚不清楚。使用各种信息学方法在 患者数据库中，我发现BC患者既有PRKCD的高表达，也有PKCD的高表达 肿瘤中CD8+T细胞或低表达MDSC基因信号的患者总存活率显著更高 与其他组相比，建议支持激活PKC。新的初步数据表明，PKC 使用FDA批准的PEP005和前列腺素的激动剂减少骨髓祖细胞产生MDSC 特别是通过激活PKC异构体。PKC激动剂诱导MDSC向CD103+DC样细胞分化 无论是体外还是体内。此外，经PEP005处理的MDSCs失去了对CD8+T细胞的抑制能力。 体外和体内的先导抑制分析和有效的交叉启动OT-I CD8+T细胞。机械论 研究表明，转录因子irf5是PKC的一个潜在靶点，将在本提案中进行探索。基于 严格生成的试点数据，我假设PKC激动剂与激动型CD40单抗相结合将 蛋白激酶C活化诱导MDSCs向DC样细胞分化增敏ICB 及其下游目标IRF5。CD40主要由髓系细胞表达，其活化已被证实 有效地激活抗原提呈细胞。AIM 1和2将确定PKC激活是否控制MDSC和 DC的表型和功能将决定PKC在多大程度上被药理联合激活 使用激动型CD40单抗可改善TNBC小鼠模型中抗PD-L1的治疗。拟议的培训将 为我的长期目标做好准备，成为一名肿瘤免疫学家，研究目标是开发新的 实体瘤的免疫调节治疗方法作为独立的研究者。

SUMMARY Immune checkpoint blockade (ICB) has revolutionized cancer therapy showing unprecedented long-term antitumor responses. However, most patients do not respond to ICB therapies due at least partly to immunosuppression. Immunotherapy non-responders have high levels of circulating myeloid-derived suppressor cells (MDSCs)- an immunosuppressive innate cell population that suppresses both innate and adaptive immunity. Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancers with poor responses to conventional therapies. TNBC patients harbor higher levels of MDSC populations compared to non-TNBC patients. Consequently, TNBC and other solid tumor patients who have high levels of circulating MDSCs respond poorly to ICB. Hence, strategies that reduce MDSC’s suppressive function while promoting cross-priming of CD8+ T cells are likely to be effectively combined with ICB for a maximum therapeutic benefit. Protein Kinase C (PKC) is a family of kinases composed of 11 isoforms that play a critical role in cell signaling. PKC delta (PKC) is the most abundant isoform in myeloid cells and plays an important role in dendritic cell (DC) function. To date, the role of PKC in myeloid cells in cancer is unknown. Using varied informatic approaches in patient databases, I found that BC patients with both high expression of PRKCD and either high expression of CD8+ T cell or low expression of MDSC gene signatures in tumors had a significantly greater overall survival compared to other groups, suggesting support for activation of PKC. Novel preliminary data suggests that PKC agonism using FDA-approved PEP005 and prostratin reduced MDSC generation from bone marrow progenitors specifically via activation of PKC isoform. PKC agonism induced MDSC differentiation to CD103+ DC-like cells both ex-vivo and in vivo. Additionally, PEP005-treated MDSCs lost their suppressive capacity on CD8+ T cells in both in vitro and in vivo pilot suppression assays and efficiently cross-primed OT-I CD8+ T cells. Mechanistic studies reveal transcription factor IRF5 as a potential target of PKC-to be explored in this proposal. Based on rigorously generated pilot data, I hypothesize that PKC agonism combined with agonistic CD40 mAb will sensitize TNBC tumors to ICB through induced differentiation of MDSCs to DC-like cells via activation of PKC and its downstream target IRF5. CD40 is mainly expressed by myeloid cells and its activation has been shown to effectively activate antigen-presenting cells. Aim 1 & 2 will determine if PKC activation controls MDSC and DC phenotype and function and will determine to what extent pharmacologic activation of PKC in combination with agonistic CD40 mAb improves anti-PD-L1 therapy in TNBC mouse models. The proposed training will prepare me for my long-term goal of becoming a tumor immunologist with a research objective to develop novel immunomodulatory therapeutic approaches against solid tumors as an independent investigator.