Aldh2 and mitochondrial homeostasis in esophageal pathobiology

项目总结 食道鳞状细胞癌(ESCC)是所有人类鳞状细胞癌中最致命的，具有 酒精是一个主要的危险因素。酒精在食道上皮细胞损伤和食管鳞癌中的作用 病理生物学仍不清楚。乙醇代谢会产生乙醛，这是人类的一种主要致癌物质。 在饮酒可能导致疾病的靶器官中，食道是独一无二的，因为它直接 暴露在高浓度的乙醇和乙醛中。酒精戒毒包括清除 乙醛通过乙醛脱氢酶2(ALDH2)，这是一种分解醛的线粒体酶。 ALDH2功能障碍会增加携带ALDH2基因突变(Aldh2E487K)个体的癌症风险。在ALDH2中-/- 和Aldh2E487K突变小鼠和ALDH2缺失的人食道上皮细胞，酒精诱导 线粒体损伤和氧化应激，DNA加合物形成和DNA损伤增加， 提示线粒体功能障碍和活性氧物种(ROS)可能参与遗传 ALDH2功能失调的食道上皮细胞的不稳定性。酒精诱导的氧化应激可通过以下方法缓解 自噬是一种细胞保护机制，可以去除受损的细胞成分，包括功能障碍 线粒体。此外，酒精刺激ESCC肿瘤生长，肿瘤起始细胞增多。 高自噬和高CD44表达(CD44H)。长期目标是识别食道粘膜 可用于预防或治疗ESCC的防御机制。这个项目的总体目标是 提案是澄清酒精如何影响患有ALDH2功能障碍的食道上皮细胞。这项建议 利用基因工程小鼠模型、患者的活检组织、具有改变ALDH2状态的人类细胞系通过 CRISPR/CAS9-入路、异种移植系列试验和一种新的三维食道器体 以酒精暴露和药理学干预为综合平台的系统，以确定 ALDH2在上皮细胞对酒精暴露反应中的机制和功能。中心假设是 ALDH2限制酒精诱导的线粒体功能障碍，抑制氧化应激和ESCC肿瘤 萌发和成长。这一假设是基于#年产生的强劲的初步数据提出的。 申请人的实验室，并将通过以下三个相互关联的具体目标进行测试：(1) 阐明线粒体ALDH2如何限制酒精诱导的食道上皮细胞损伤；(2)如何定义 自噬减少酒精诱导的线粒体损伤和氧化应激；(3)确定ALDH2是如何 影响酒精诱导的食道肿瘤特性。这些创新的研究将揭示新的 ALDH2功能障碍在酒精性氧化应激和食道上皮细胞中的作用 在ESCC和其他酒精性疾病的发病机制中，损伤以及自噬介导的细胞保护， 无论是良性还是恶性。

PROJECT SUMMARY Esophageal squamous cell carcinoma (ESCC) is the deadliest of all human squamous cell carcinomas with alcohol as a major risk factor. The role of alcohol (ethanol) in the esophageal epithelial cell injury and ESCC pathobiology remains unknown. Ethanol metabolism produces acetaldehyde, a major human carcinogen. Amongst the target organs alcohol drinking may cause diseases, esophagus is unique because it is directly exposed to high concentrations of EtOH and acetaldehyde. Alcohol detoxification involves clearance of acetaldehyde via aldehyde dehydrogenase 2 (Aldh2), the mitochondrial enzyme which breaks down aldehydes. Aldh2 dysfunction increases cancer risk in individuals with polymorphic Aldh2 mutation (Aldh2E487K). In Aldh2-/- and Aldh2E487K mutant mice and Aldh2-depleted human esophageal epithelial cells, alcohol induces mitochondrial damage and oxidative stress with increased DNA adducts formation and DNA damage, suggesting that mitochondrial dysfunction and reactive oxygen species (ROS) may contribute to genetic instability in Aldh2 dysfunctional esophageal epithelial cells. Alcohol-induced oxidative stress is alleviated by autophagy, a cytoprotective mechanism which removes damaged cellular components including dysfunctional mitochondria. Moreover, alcohol stimulates ESCC tumor growth with increased tumor-initiating cells displaying high autophagy and high CD44 expression (CD44H). The long-term goal is to identify esophageal mucosal defense mechanisms that can be manipulated for prevention or therapy of ESCC. The overall objective in this proposal is to clarify how alcohol affects esophageal epithelial cells with Aldh2 dysfunction. This proposal utilizes genetically engineered mouse models, patients' biopsies, human cell lines with altered Aldh2 status via the CRISPR/Cas9-approach, xenograft serial transplantation assays and a novel 3D esophageal organoid system with ethanol exposure and pharmacological interventions as a comprehensive platform to define the mechanistic and functional role of Aldh2 in epithelial response to alcohol exposure. The central hypothesis is that Aldh2 limits alcohol-induced mitochondrial dysfunction, suppressing oxidative stress and ESCC tumor initiation and growth. This hypothesis has been formulated on the basis of strong preliminary data produced in the applicant's laboratory and will be tested by pursuing the following three interrelated Specific Aims: (1) To clarify how mitochondrial Aldh2 limits alcohol-induced esophageal epithelial cell injury; (2) To define how autophagy reduces alcohol-induced mitochondrial damage and oxidative stress; (3) To determine how Aldh2 influences alcohol-induced esophageal neoplastic characteristics. These innovative studies will reveal novel insight into the role of dysfunctional Aldh2 in alcohol-induced oxidative stress and esophageal epithelial cell injury as well as autophagy-mediated cytoprotection in the pathogenesis of ESCC and other alcoholic diseases, both benign and malignant.