BARX1基因及其遗传变异在食管鳞癌发生中的作用机制研究

In 2013, a genome wide association study (GWAS) identified several susceptibility loci for esophageal adenocarcinoma in Caucasian population. Our study found that genetic variants in 9q22 (BARX1) were significantly associated with the risk of esophageal squamous cell carcinoma and these variants can influence BARX1 expression. In addition, we detected an elevated expression level of BARX1 in esophageal cancer tissue. Based on these evidences, we hypothesize that genetic variants in 9q22 may affect esophageal cancer pathogenesis by inducing the abnormal expression of BARX1 and further result in diverse esophageal cancer risk for subject with different genotype of BARX1. The current project is going to conduct a fine-mapping strategy to explore the association between genome structure and genetic variation of 9q22 loci and esophageal squamous carcinoma risk based on targeted sequencing. Then we plan to evaluate the regulatory mechanisms of relevant variants in BARX1 transcription using bioinformatics and molecular biology methods. In combination with cell and animal model, we further plan to investigate the effects of changed expression level of BARX1 on proliferation, invasion, migration, apoptosis and cell cycle regulation mechanisms in esophageal carcinogenesis. These efforts will facilitate elucidating development of esophageal cancer, developing new drugs, and finally promoting the prevention and treatment level for esophageal cancer.

2013年高加索裔人群的一项全基因组关联研究发现了多个食管腺癌的易感区域。本课题组前期通过大样本人群研究发现位于染色体9q22区域BARX1基因的遗传变异也与中国人群食管鳞癌易感性相关，并且该遗传变异影响BARX1蛋白的表达，而BARX1蛋白在食管鳞癌组织中显著高表达。因此，我们提出：染色体9q22区域的遗传变异可能通过调控BARX1基因表达影响食管鳞癌发生，从而导致携带不同基因型的个体发生食管鳞癌的风险存在差异。本课题拟首先通过高通量目标区域测序技术对BARX1基因区域开展精细定位研究，解析该区域影响食管癌发病风险的遗传结构和变异；进而利用生物信息学分析和分子生物学实验，探讨这些遗传变异影响BARX1基因表达的调控机制；同时应用细胞实验和动物模型揭示BARX1基因参与食管癌发生发展进程的机制。本研究成果将为食管癌发生机制的阐明、新型药物的研发以及最终防治水平的提高奠定基础。

2013年高加索裔人群的一项全基因组关联研究发现了4个食管腺癌的易感区域。为探讨这4个易感区域是否与中国人群食管鳞癌发病也相关，本研究首先在2,139例食管鳞癌病例和2,463例健康对照中，对这4个易感位点进行关联研究。结果发现只有位于染色体9q22区域的rs11789015与中国人群食管鳞癌发病也显著相关。生物信息学分析发现该易感位点位于BARX1基因启动子区域，并且该遗传变异A>G的改变可显著降低BARX1的mRNA和蛋白表达水平，同时报告基因实验也证实rs11789015的G等位基因可以显著降低所在区域启动子活性。而相较于癌旁组织，BARX1的mRNA和蛋白水平在食管鳞癌组织中显著高表达；此外，应用TCGA食管鳞癌数据库，将与BARX1存在显著共表达关系的基因进行kegg通路富集分析，发现显著富集于包括IL-17信号通路、Toll样受体信号通路等在内的免疫相关通路。进一步应用CRISPR/Cas9技术在食管鳞癌细胞系ECA109敲除BARX1后，发现敲除细胞系的增殖、迁移和侵袭能力均显著减弱，提示BARX1的癌基因作用。本研究最终证实位于染色体9q22区域的rs11789015可通过影响启动子活性调控BARX1基因的表达从而影响中国人群食管鳞癌的易感性。