The Role of Secondary Bile Acids in Gastro-Esophageal Neoplasia

项目概要 胃食管交界处 (GEJ) 的干细胞和祖细胞已被确定对于 远端食管、胃食管交界处和近端胃的腺癌的发展。 加起来，这些癌症在美国每年新增病例超过 20,000 例，死亡率很高，而且 是一项重大的公共卫生负担。我们的小组已经确定了胃贲门和 GEJ 移行 基底干细胞可能是该区域癌前状态的起源细胞。然而，定义机制 驱动 GE 连接干细胞命运和促进癌症发展的效应器仍然是一个关键的空白 知识。巴雷特食管 (BE) 和食管腺癌 (EAC) 代表了食管癌的原型 由GE连接干细胞产生的肿瘤。我们有大量的初步数据表明，流通 来自肠道细菌的次级胆汁酸直接促进 BE 和 EAC 的发展，治疗我们的 L2-IL1B BE/EAC 小鼠模型与脱氧胆酸 (DCA) 加速肿瘤形成，并且治疗 奥贝胆酸是核胆汁酸受体 FXR（法尼醇 X 受体）的激动剂，可减少增殖， GEJ 干细胞数量和发育不良。然而，次级胆汁酸影响的确切机制 GEJ 干细胞和相关的微环境尚未阐明。我们假设循环 肠道细菌产生的次级胆汁酸通过对 GE 的直接影响促进早期癌症的发展 连接干细胞通过 FXR 拮抗作用和诱导促炎微环境改变。 使用高度新颖的技术和方法（包括 scRNA-Seq 和 CyTOF），我们将进行一系列 使用小鼠模型、小鼠和人类类器官进行实验，并对研究结果进行前瞻性验证 对患者进行研究，以解决以下具体目标： 目标 1. 确定循环继发性循环的作用 胆汁酸在 GEJ 上皮干细胞命运和早期癌症促进中的作用；目标 2. 评估循环的影响 次级胆汁酸对 GEJ 上皮干细胞微环境的影响；目标3.确定是否有针对性 调节循环胆汁酸池的微生物组修饰可改变 GEJ 癌症的发展。至 为了实现这些目标，我们将使用我们独特的 L2-IL1B 小鼠模型，在干细胞中敲除 FXR（L2- IL1B/Fxrfl/fl)，使我们能够评估次级胆汁酸对 GEJ 干细胞以及 L2-IL1B/Nlrpfl/fl 的影响 模型探索干细胞中炎症小体的激活并评估与微环境的串扰。 最终，我们将进行用高度特征化的细菌菌株的独特联合体进行治疗的实验 调节肠道微生物组的次级胆汁酸产生能力并确定对 由 GE 连接干细胞产生的癌症。阐明次级胆汁的具体机制 酸与 GEJ 干细胞相互作用并改变微环境以促进癌症发展可能会导致 确定新的治疗靶点，包括合理设计益生菌疗法的潜力， 这将对公共卫生产生重大影响。

PROJECT SUMMARY Stem and progenitor cells at the gastroesophageal junction (GEJ) have been identified as crucial to the development of adenocarcinoma of the distal esophagus, gastroesophageal junction, and proximal stomach. Combined, these cancers have over 20,000 new cases per year in the U.S., are associated high mortality, and represent a major public health burden. Our group has identified both gastric cardia as well as GEJ transitional basal stem cells as likely cells of origin for precancerous states in this region. However, defining the mechanisms and effectors that drive GE junction stem cell fate and promote cancer development remains a critical gap in knowledge. Barrett’s esophagus (BE) and esophageal adenocarcinoma (EAC) represent the prototype for neoplasia arising from GE junction stem cells. We have extensive preliminary data demonstrating that circulating secondary bile acids derived from gut bacteria directly promote the development of BE and EAC, treating our L2-IL1B mouse model of BE/EAC with deoxycholic acid (DCA) accelerates neoplasia, and treatment with obeticholic acid, an agonist of nuclear bile acid receptor FXR (farnesoid X receptor), decreases proliferation, GEJ stem cell numbers, and dysplasia. However, the exact mechanisms by which secondary bile acids impact GEJ stem cells and the associated microenvironment have not been elucidated. We hypothesize that circulating secondary bile acids produced by gut bacteria promote early cancer development via direct effects on GE junction stem cells through FXR antagonism and by inducing pro-inflammatory microenvironment alterations. Using highly novel techniques and approaches (including scRNA-Seq and CyTOF), we will perform a series of experiments using mouse models, mouse and human organoids, and with validation of findings in a prospective study of patients, to address the following specific aims: Aim 1. To determine the role of circulating secondary bile acids in GEJ epithelial stem cell fate and early cancer promotion; Aim 2. To assess the effects of circulating secondary bile acids on the GEJ epithelial stem cell microenvironment; Aim 3. To determine whether targeted microbiome modification that regulates the circulating bile acid pool modifies GEJ cancer development. To achieve these aims we will use our unique L2-IL1B mouse model with FXR knockout in stem cells (L2- IL1B/Fxrfl/fl), allowing us to assess the effects of secondary bile acids on GEJ stem cells as well the L2-IL1B/Nlrpfl/fl model to explore inflammasome activation in stem cells and assess for cross-talk with the microenvironment. Ultimately, we will perform experiments treating with distinct consortia of highly characterized bacterial strains to modulate the secondary bile acid producing capacity of the gut microbiome and determine the effects on cancers arising from GE junction stem cells. Elucidation of the specific mechanisms by which secondary bile acids interact with GEJ stem cells and modify the microenvironment to promote cancer development may lead to the identification of novel therapeutic targets, including the potential for rationally designed probiotic therapy, which would have a major public health impact.