The role of the gut microbiome in ICB-induced anti-tumor response and toxicity

项目总结 免疫检查点阻断(ICB)通过诱导持久反应和 提高包括黑色素瘤在内的多种癌症的存活率。然而，只有一部分患者 目前尚不清楚是什么因素决定了患者对治疗的反应。此外，ICB还可导致免疫- 相关不良事件(IrAEs)，限制治疗并导致靶外组织毒性。联合治疗与 抗细胞毒T淋巴细胞相关蛋白4(-CTLA-4)和抗程序性死亡配体1(-PD-L1) 与单一药物治疗相比，在存活率方面显示出最强的疗效，但这与 具有更高的IRAE频率。最近的研究已经描述了肠道微生物群在发挥作用方面的作用 ICB反应性的生物标志物，一种潜在的治疗方法，在某些情况下与irAEs相关。有了这个 建议，我们的目的是增加对联合ICB肠道微生物-免疫系统轴的理解 心理治疗。我们实验室最近的工作强调了树突状细胞(DC)的作用，这是一种专业的抗原递呈 免疫系统的细胞(APC)，在ICB反应中，以及ICB相关的irAEs。此外，我们发现， 抗生素治疗对肠道微生物群的调节改变了对-CTLA-4的反应：使用甲硝唑 经-CTLA-4治疗后肿瘤消退约90%。此外， -CTLA-4在甲硝唑治疗条件下的疗效与1型常规治疗的增加相关 DC(CDc1)的数量和激活状态，与先前的临床研究一致，表明cDc1在 黑色素瘤患者的ICB反应良好。因此，我们假设肠道内的特定微生物 微生物群诱导cDC1s活性增加，调节对ICB治疗的有利反应 而且，一旦失调，就会导致ICB介导的结肠炎。我们建议分两个阶段来检验这一假设 目标。在目标1中，我们将确定APC在连接肠道微生物组和icb介导的抗肿瘤中的作用。 豁免权。我们将利用黑色素瘤患者的粪便样本来重新填充抗生素的肠道微生物群- 处理小鼠(粪便微生物组移植，FMT)。我们将评估微生物组组成、免疫细胞 联合ICB治疗的黑色素瘤荷瘤小鼠的肠道炎症(IrAEs)。此外, CDC1s缺陷的小鼠将被用来检查这一亚群APC在ICB反应和 使用患者衍生材料进行FMT后的毒性。在目标2中，我们试图描述 甲硝唑及其对微生物组和ICB反应的影响。我们将使用来自患者的材料进行FMT 从无应答者和甲硝唑治疗中检查厌氧菌是否通过 甲硝唑足以将无应答者转变为应答者。我们将进一步检查微生物组 成分，并确定与甲硝唑治疗时免疫细胞状态和活性的联系。我们的研究将 描述人类粪便样本中的特定微生物是否与关键免疫特征或irAEs相关， 从而加深了对肠道微生物群调节ICB反应的机制的理解。

PROJECT SUMMARY Immune checkpoint blockade (ICB) has transformed clinical oncology by inducing durable responses and increasing survival rates in many types of cancers, including melanoma. However, only a subset of patients benefits, and it is unclear what determines a patient’s response to therapy. In addition, ICB can lead to immune- related adverse events (irAEs) that limit therapy and cause off-target tissue toxicities. Combination therapy with anti-cytotoxic T-lymphocyte associated protein 4 (-CTLA-4) and anti-programmed death ligand 1 (-PD-L1) exhibits the strongest efficacy, in terms of survival, compared with single agent treatments, yet this is associated with a greater irAE frequency. Recent studies have delineated roles for the gut microbiome in serving as a biomarker of ICB responsiveness, a potential therapeutic, and in some cases association with irAEs. With this proposal, we aim to increase understanding of the gut microbiome-immune system axis in combination ICB therapy. Recent work from our lab has highlighted roles for dendritic cells (DCs), professional antigen-presenting cells (APCs) of the immune system, in ICB response as well as ICB-associated irAEs. Moreover, we found that modulation of the gut microbiome via antibiotic treatment altered response to -CTLA-4: use of metronidazole prior to ICB resulted in ~90% tumor regression upon -CTLA-4 treatment without intestinal irAE. In addition, the efficacy of -CTLA-4 in metronidazole treatment conditions was associated with increases in type 1 conventional DC (cDC1) amounts and activation status, consistent with prior clinical studies implicating a role for cDC1s in favorable ICB response in melanoma patients. Thus, we hypothesize that specific microbes within the gut microbiome induce increased activity of cDC1s, which regulate favorable responses to ICB treatment and, upon dysregulation, contribute to ICB-mediated colitis. We propose to examine this hypothesis in two aims. In Aim 1, we will identify the role of APCs in linking the gut microbiome to ICB-mediated anti-tumor immunity. We will utilize fecal samples from melanoma patients to repopulate the gut microbiome of antibiotic- treated mice (fecal microbiome transplantation, FMT). We will evaluate microbiome composition, immune cell profiles, and intestinal inflammation (irAEs) in melanoma-bearing mice treated with combination ICB. In addition, mice with a deficiency of cDC1s will be used to examine roles for this subset of APCs in ICB response and toxicity following FMT with patient-derived material. In Aim 2, we seek to characterize the relationship between metronidazole and effect on the microbiome and ICB response. We will utilize FMT with patient-derived material from non-responders and metronidazole treatment to examine whether depletion of anaerobic bacteria via metronidazole is sufficient to convert a non-responder into a responder. We will further examine the microbiome composition and identify links to immune cell status and activity upon metronidazole treatment. Our studies will delineate whether specific microbes from human fecal samples correlate with key immune signatures or irAEs, thereby deepening understanding of mechanisms by which the gut microbiome regulates ICB responsiveness.