Dissecting the Myeloid-Th17 axis in the pathogenesis of Colitis-associated Colorectal Cancer

在美国，结直肠癌(CRC)是癌症相关死亡的第二大原因。慢性 肠道炎症是散发性和结肠炎发生和发展的主要危险因素- 相关性结直肠癌(CAC)。而促肿瘤炎症的致病作用是广泛的 认识到，推动这一过程的机制，包括细胞和分子介体，是很差的 明白了。这具有治疗意义，特别是在结直肠癌中，目前可用的T细胞检查点 抑制剂的益处是有限的。在初步研究中，我们使用了偶氮甲烷/葡聚糖硫酸钠模型 允许询问启动促进事件的炎症驱动的结肠癌发生 支撑着CAC的发展。我们观察到，与周围的非肿瘤结肠相比， 肿瘤微环境富含肿瘤浸润性髓样细胞(TIM)，包括中性粒细胞(PMN)， 单核细胞和肿瘤相关巨噬细胞(TAMs)。PMN是主要人群，并且 而单核细胞/TAMs(M)似乎依赖于CC-CCR2途径。 这两个亚群都表达促炎和免疫抑制基因，从而表明它们的促炎基因 致癌作用。此外，肿瘤微环境中白介素17的含量增加。 产生CD4+T细胞(Th17)和γ-增量T细胞。IL-17是促进结直肠癌的促炎细胞因子 生长和表达增加与预后不良有关。先前的研究表明，TIMs促进 Th17通过产生IL-23(IL-23A/IL-12B杂二聚体)而发展。然而，我们的单细胞RNA 测序研究表明，虽然PMN表达IL23a，但它们不表达IL12b，从而表明 无法产生有功能的IL-23。取而代之的是，PMN表达EB病毒诱导基因3(Ebi3) 最近发现它与IL-23A二聚化形成IL-39，这是一种促炎细胞因子。我们 假设髓系-Th17轴对于维持炎性微环境是至关重要的 帮助维持CAC进展。我们提出在肿瘤微环境中存在前馈环路。 因此，PMN和M-协同工作，促进Th17的发展，进而产生IL-17， 在肿瘤中招募和维持更多的PMN和M-，从而加强炎症微环境 这推动了CAC的发展。破坏这一循环的机制将是我们提案的重点。我们的首要目标是 探讨TIMS在CAC发病机制中的作用 PMN和M-在肿瘤发展中的募集(Aim IA)或它们在已建立的肿瘤中的缺失(Aim IB)。在……里面 我们的第二个目标，我们将探索IL-39作为Th17发展的替代机制的作用(Aim IIA) 并评估其在肿瘤发展中的作用(AIM IIB)，包括细胞特异性缺失Ebi3在 中性粒细胞和CD4+T细胞(AIM IIC)。这些研究将对慢性阻塞性肺疾病患者的治疗策略产生影响 CAC和其他免疫介导性疾病，如炎症性肠病。

Colorectal cancer (CRC) is the second-leading cause of cancer-related mortality in the United States. Chronic intestinal inflammation is a major risk factor for the development and progression of sporadic and colitis- associated colorectal cancer (CAC). While the pathogenic effects of tumor-promoting inflammation are widely recognized, the mechanisms driving this process, including the cellular and molecular mediators are poorly understood. This has therapeutic implications especially in CRC where the currently available T-cell checkpoint inhibitors have a limited benefit. In preliminary studies, we used the azoxymethane/ dextran sulfate sodium model of inflammation-driven colon carcinogenesis that allows interrogation of the initiation-promotion events underpinning the development of CAC. We observed that compared to the surrounding non-tumor-bearing colon, the tumor microenvironment is enriched with tumor-infiltrating myeloid (TIM) cells, including neutrophils (PMNs), monocytes, and tumor-associated macrophages (TAMs). PMNs are the predominant population and are recruited through the Cxc-Cxcr2 axis while the monocytes/TAMs (M) appear to rely on the Cc-Ccr2 pathway. Both subsets express pro-inflammatory and immune-suppressive genes thereby suggesting their pro- tumorigenic role. Additionally, the tumor microenvironment has an increased abundance of interleukin (IL)-17 producing CD4+ T (Th17) and gamma-delta T cells. IL-17 is a pro-inflammatory cytokine that promotes CRC growth and increased expression is associated with poor prognosis. Previous studies indicate that TIMs promote Th17 development through the production of IL-23 (IL-23A/IL-12B heterodimer). However, our single-cell RNA sequencing studies revealed that while the PMNs expressed Il23a, they did not express Il12b thereby suggesting an inability to produce functional IL-23. Instead, the PMNs expressed Epstein-Barr virus-induced gene 3 (Ebi3) which has recently been shown to dimerize with IL-23A to form IL-39, a pro-inflammatory cytokine. We hypothesize that the myeloid-Th17 axis is critical for the maintenance of an inflammatory microenvironment that helps sustain CAC progression. We propose the existence of a feed-forward loop in the tumor microenvironment whereby the PMNs and M work synergistically to promote Th17 development, and the resulting IL-17, in turn, recruits and maintains more PMNs and M in the tumor thereby reinforcing an inflammatory microenvironment which fuels CAC progression. Mechanisms to disrupt this loop will be the focus of our proposal. Our first aim will attempt to define the role of TIMs in the pathogenesis of CAC by exploring the effects of blocking colonic recruitment of PMNs and M on tumor development (Aim IA) or their deletion in established tumors (Aim IB). In our second aim, we will explore the role of IL-39 as an alternative mechanism of Th17 development (Aim IIA) and assess its role in tumor development (Aim IIB), including the effects of cell-specific deletion of the Ebi3 in PMNs and CD4+T cells (Aim IIC). These studies will have implications in treatment strategies for patients with CAC and other immune-mediated diseases like inflammatory bowel disease.