Department of Molecular Pathology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
Exp Mol Pathol. 2012 Aug;93(1):35-9. doi: 10.1016/j.yexmp.2012.03.012. Epub 2012 Mar 24.
AFP-producing adenocarcinoma is a variant of adenocarcinoma with high malignancy. Production of AFP suggests enteroblastic or hepatoid differentiation of cancer cells. GATA4 is a key molecule involved in the prenatal development of the stomach and liver. GATA4 is epigenetically silenced by hypermethylation of primer region in many types of cancers including gastric cancer. The aim of this study is to investigate the expression and epigenetic regulation of GATA4 in AFP-producing adenocarcinoma. Immunohistochemical analysis revealed that GATA4 was positive in 3/8 cases of AFP-producing gastric adenocarcinomas and in 28/30 cases of common type adenocarcinomas. Epigenetic modification of GATA4 promoter region was investigated with 3 AFP-producing and 4 common-type gastric cancer cell lines. GATA4 mRNA was detected in 1/3 of AFP-producing and 2/4 of common-type gastric cancer cell lines by RT-PCR. Methylation-specific PCR revealed no GATA4 methylation in any of the AFP-producing gastric cancers, whereas methylation was consistent with GATA4 expression in the common-type gastric cancers. Chromatin immunoprecipitation assay for AFP-producing gastric cancers revealed that histones H3 and H4 were hypoacetylated in the GATA4-negative cells, while they were hyperacetylated in the GATA4-positive cells. Treatment with trichostain A, an inhibitor for histone deacetylase, induced acetylation of histones H3 and H4, and tri-methylation of lysine 4 of histone H3, which was associated with the active transcription of GATA4 in GATA4-negative AFP-producing cells. These results indicated that histone deacetylation is a silencing mechanism for GATA4 expression in AFP-producing gastric cancer cells. Differences between AFP-producing gastric cancer and common-type gastric cancer in terms of the mechanism of GATA4 regulation may be reflected in the phenotypic deviation of AFP-producing gastric cancer from common-type gastric cancer.
甲胎蛋白（AFP）产生性腺癌是一种高度恶性的腺癌变异体。AFP 的产生提示癌细胞具有肠胚层或肝细胞分化。GATA4 是参与胃和肝产前发育的关键分子。GATA4 在包括胃癌在内的许多类型的癌症中通过启动子区域的高度甲基化而被表观遗传沉默。本研究旨在探讨 AFP 产生性腺癌中 GATA4 的表达和表观遗传调控。免疫组织化学分析显示，在 8 例 AFP 产生的胃腺癌中有 3 例和 30 例常见型腺癌中有 28 例 GATA4 阳性。研究了 3 例 AFP 产生和 4 例常见型胃癌细胞系中 GATA4 启动子区域的表观遗传修饰。通过 RT-PCR 在 1/3 的 AFP 产生和 2/4 的常见型胃癌细胞系中检测到 GATA4 mRNA。甲基化特异性 PCR 显示在任何 AFP 产生的胃癌中均未发现 GATA4 甲基化，而在常见型胃癌中则与 GATA4 表达一致。对 AFP 产生的胃癌进行染色质免疫沉淀分析显示，在 GATA4 阴性细胞中组蛋白 H3 和 H4 低乙酰化，而在 GATA4 阳性细胞中高乙酰化。用组蛋白去乙酰化酶抑制剂 Trichostain A 处理可诱导组蛋白 H3 和 H4 的乙酰化以及组蛋白 H3 赖氨酸 4 的三甲基化，与 GATA4 阴性 AFP 产生细胞中 GATA4 的转录激活相关。这些结果表明，组蛋白去乙酰化是 AFP 产生胃癌细胞中 GATA4 表达的沉默机制。AFP 产生胃癌和常见型胃癌在 GATA4 调控机制方面的差异可能反映在 AFP 产生胃癌从常见型胃癌的表型偏差。
