Department of Molecular Oncology, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo.
Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo.
Carcinogenesis. 2020 Jul 10;41(6):734-742. doi: 10.1093/carcin/bgz179.
Genomic analyses have recently discovered the malignant subtype of human intrahepatic cholangiocarcinoma (ICC) characterized by frequent mutations of chromatin remodeling gene ARID1A; however, the biological and molecular functions still remain obscure. We here examined the clinical and biological significances of ARID1A deficiency in human ICC. Immunohistochemical analysis demonstrated that the loss of ARID1A was an independent prognostic factor for overall survival of ICC patients (P = 0.023). We established ARID1A-knockout (KO) cells by using the CRISPR/Cas9 system from two human cholangiocarcinoma cell lines. ARID1A-KO cells exhibited significantly enhanced migration, invasion, and sphere formation activity. Microarray analysis revealed that ALDH1A1, a stemness gene, was the most significantly elevated genes in ARID1A-KO cells. In addition, ALDH enzymatic activity as a hallmark of cancer stem cells was markedly high in the KO cells. ARID1A and histone deacetylase 1 were directly recruited to the ALDH1A1 promoter region in cholangiocarcinoma cells with undetectable ALDH1A1 expression by chromatin immunoprecipitation assay. The histone H3K27 acetylation level at the ALDH1A1 promoter region was increased in cells when ARID1A was disrupted (P < 0.01). Clinically, inverse correlation between ARID1A and ALDH1A1 expression was also identified in primary ICC (P = 0.018), and ARID1A-negative and ALDH1A1-positve ICCs showed worse prognosis than only ARID1A-negative cases (P = 0.002). In conclusion, ARID1A may function as a tumor suppressor in ICC through transcriptional downregulation of ALDH1A1 expression with decreasing histone H3K27 acetylation. Our studies provide the basis for the development of new epigenetic approaches to ARID1A-negative ICC. Immunohistochemical loss of ARID1A is an independent prognostic factor in intrahepatic cholangiocarcinoma patients. ARID1A recruits HDAC1 to the promoter region of ALDH1A1, a stemness gene, and epigenetically suppresses ALDH1A1 expression with decreasing histone H3K27 acetylation in cholangiocarcinoma cells.
基因组分析最近发现了人类肝内胆管癌（ICC）的恶性亚型，其特征是染色质重塑基因 ARID1A 的频繁突变；然而，其生物学和分子功能仍然不清楚。我们在这里研究了 ARID1A 缺失在人类 ICC 中的临床和生物学意义。免疫组织化学分析表明，ARID1A 的缺失是 ICC 患者总生存的独立预后因素（P=0.023）。我们使用 CRISPR/Cas9 系统从两种胆管癌细胞系中建立了 ARID1A 敲除（KO）细胞。ARID1A-KO 细胞表现出明显增强的迁移、侵袭和球体形成活性。微阵列分析显示，ALDH1A1，一个干性基因，是 ARID1A-KO 细胞中最显著上调的基因。此外，在 KO 细胞中，作为癌症干细胞标志的 ALDH 酶活性明显升高。染色质免疫沉淀分析显示，在胆管癌细胞中，ARID1A 和组蛋白去乙酰化酶 1 直接被招募到 ALDH1A1 启动子区域，而在 ALDH1A1 表达不可检测的细胞中则没有。当 ARID1A 被破坏时，ALDH1A1 启动子区域的组蛋白 H3K27 乙酰化水平增加（P<0.01）。临床上，在原发性 ICC 中也发现了 ARID1A 和 ALDH1A1 表达的负相关（P=0.018），并且 ARID1A 阴性和 ALDH1A1 阳性的 ICC 比仅 ARID1A 阴性的病例预后更差（P=0.002）。总之，ARID1A 可能通过下调 ALDH1A1 表达并降低组蛋白 H3K27 乙酰化来抑制肿瘤生长，从而在 ICC 中发挥肿瘤抑制作用。我们的研究为开发针对 ARID1A 阴性 ICC 的新表观遗传方法提供了依据。免疫组化检测到 ARID1A 缺失是肝内胆管癌患者的独立预后因素。ARID1A 将 HDAC1 募集到 ALDH1A1 启动子区域，该基因是一个干性基因，并通过降低组蛋白 H3K27 乙酰化来表观遗传抑制胆管癌细胞中 ALDH1A1 的表达。
