Basic and Clinical Studies on the Role of Bile Acids in Barrett's Esophagus

描述（由申请人提供）：胃食管反流病（GERD）和巴雷特食管（BE）是美国成年人中非常常见的疾病，是食管腺癌的重要危险因素。在过去的几十年里，BE相关腺癌的发病率增加了6倍以上，由于对BE发病机制和肿瘤进展的分子事件了解有限，这种致命肿瘤的化学预防治疗的发展受到阻碍。我们的初步数据显示，Barrett上皮细胞比通常排列在食道上的鳞状细胞更能抵抗脱氧胆酸（DCA）（一种在反流胃液中发现的疏水胆汁酸）诱导的细胞凋亡。这种凋亡抵抗可能是Barrett化生的发病机制和持久性的基础，因为胆汁酸诱导的食管鳞状细胞凋亡被抗凋亡的Barrett细胞所取代。像DCA这样的疏水胆汁酸也被证明会导致DNA损伤，而广泛的DNA损伤通常会引发细胞凋亡。然而，我们从体外和体内研究中获得的初步数据表明，巴雷特细胞通过激活抗凋亡存活途径对胆汁酸诱导的DNA损伤做出反应。这可以促进巴雷特化生的肿瘤进展，因为它允许持续的促癌突变细胞存活。此外，我们的初步研究表明，与非BE患者的食管鳞状细胞相比，BE患者的食管鳞状细胞可能更容易受到DNA损伤诱导的凋亡。食管鳞状细胞易发生细胞凋亡也可能导致BE的发生。我们的初步数据表明NF-kB通路在Barrett化生的凋亡抵抗中起关键作用。我们也有初步的数据显示熊去氧胆酸（UDCA）是一种亲水性胆汁酸，在体外或体内都不会引起Barrett细胞的基因毒性损伤，甚至可以防止DCA暴露引起的DNA损伤。这些发现提示UDCA具有潜在的化学预防作用。最近，我们利用端粒酶技术从伴有和不伴有BE的胃食管反流患者中产生了不朽但良性（未转化）的巴雷特细胞系和食管鳞状细胞系。我们建议利用这些细胞系和组织标本来探索胆汁酸反流激活的调节细胞凋亡的分子途径，以及这些途径在BE发生和肿瘤进展中的作用。我们假设胆汁酸通过影响NF-:B通路影响食管细胞凋亡。本研究旨在探讨胆汁酸对体外和体内正常食管鳞状和化生巴雷特细胞DNA损伤、NF-:B通路和凋亡的影响，破坏关键的NF-:B蛋白，并确定这些破坏对胆汁酸介导的体外细胞凋亡的影响，并确定UDCA是否可以防止胆汁酸对体外DNA损伤和细胞凋亡的影响。公共卫生相关性：对公共卫生的相关性是鉴定特定的分子标记物，这些分子标记物可用于选择可能从积极的抗反流治疗中获益的胃食管反流病患者亚群，以防止Barrett食管的发展，以及选择从干预措施中获益最多的Barrett食管患者亚群，以预防食管腺癌。

DESCRIPTION (provided by applicant): Gastroesophageal reflux disease (GERD) and Barrett's esophagus (BE), which are exceptionally common disorders in adult Americans, are strong risk factors for esophageal adenocarcinoma. The frequency of BE- associated adenocarcinoma has increased more than six-fold in the past few decades, and the development of chemopreventive therapies for this lethal tumor has been hampered by limited understanding of the molecular events underlying the pathogenesis and neoplastic progression of BE. We have preliminary data showing that Barrett's epithelial cells are more resistant to apoptosis induced by deoxycholic acid (DCA), a hydrophobic bile acid found in refluxed gastric juice, than the squamous cells that normally line the esophagus. Such apoptotic resistance might underlie the pathogenesis and persistence of Barrett's metaplasia, as esophageal squamous cells that succumb to bile acid-induced apoptosis are replaced by apoptosis-resistant Barrett's cells. Hydrophobic bile acids like DCA also have been shown to cause DNA damage, and extensive DNA damage normally triggers apoptosis. However, we have preliminary data from in vitro and in vivo studies showing that Barrett's cells respond to bile acid-induced DNA damage by activating anti-apoptotic survival pathways. This could facilitate the neoplastic progression of Barrett's metaplasia by allowing the survival of cells that have sustained cancer-promoting mutations. Moreover, our preliminary studies suggest that esophageal squamous cells from patients with BE may be more susceptible to apoptosis induced by DNA damage than esophageal squamous cells from GERD patients without BE. This predisposition of esophageal squamous cells to succumb to apoptosis also may contribute to the development of BE. Our preliminary data suggest that the NF-kB pathway plays a key role in the apoptotic resistance of Barrett's metaplasia. We also have preliminary data showing that ursodeoxycholic acid (UDCA), a hydrophilic bile acid, does not induce genotoxic damage in Barrett's cells in vitro or in vivo, and even protects against the DNA damage caused by DCA exposure. These findings suggest a potential chemopreventive role for UDCA. Recently, we have used telomerase technology to generate immortal, but benign (non-transformed), Barrett's cell lines and esophageal squamous cell lines from GERD patients with and without BE. We propose to use these cell lines as well as tissue specimens to explore the molecular pathways activated by bile-acid reflux that regulate apoptosis, and the role of those pathways in the development and neoplastic progression of BE. We hypothesize that bile acids influence apoptosis in esophageal cells through effects on the NF-:B pathway. The aims of this study are to delineate the effects of bile acids on DNA damage, on the NF-:B pathway, and on apoptosis in normal esophageal squamous and metaplastic Barrett's cells in vitro and in patients in vivo, to disrupt the key NF-:B proteins and determine the effects of those disruptions on bile-acid mediated apoptosis in vitro, and to determine whether UDCA can protect against the effects of the more toxic bile acids on DNA injury and apoptosis in vitro. PUBLIC HEALTH RELEVANCE: The relevance to public health is the identification of specific molecular markers that can be used to select a subset of our many patients with gastroesophageal reflux disease who might benefit from aggressive anti- reflux therapies to prevent the development of Barrett's esophagus as well as to select a subgroup of patients with Barrett's esophagus who would benefit most from interventions to prevent esophageal adenocarcinoma.