From the Institute of Pathology, University Hospital Heidelberg (BG, MR, WW, PS); Division of Epigenomics and Cancer Risk Factors, German Cancer Research Center (DKFZ) (CRS, LG, CD, PS, OP, CP); Department of Neuropathology, University of Heidelberg (DC); Clinical Cooperation Unit Neuropathology, German Cancer Research Center (DKFZ) (DC, WW); and Department of Neuroradiology, University of Heidelberg (MNV), Heidelberg; Edinger Institute, University Hospital Frankfurt a.M., Frankfurt (CZ, JZ, PNH, MM); and Division of Neurosurgical Research, Department of Neurosurgery, University of Heidelberg (BC); and Department of Neurooncology, Neurology Clinic and National Center for Tumor Diseases, University of Heidelberg (WW), Heidelberg, Germany; Department of Neurology, University Hospital Zurich, Zurich, Switzerland (MW); and Department of Neuropathology, Institute of Pathology and Neuropathology, Eberhard-Karls-University of Tübingen, Tübingen (RM, JS); and Department of Sports Medicine, Rehabilitation and Disease Prevention, Johannes Gutenberg University, Mainz (PS), Germany.
J Neuropathol Exp Neurol. 2013 Oct;72(10):933-41. doi: 10.1097/NEN.0b013e3182a59a88.
The scaffold protein A-kinase anchor protein 12 (AKAP12) exerts tumor suppressor activity and is downregulated in several tumor entities. We characterized AKAP12 expression and regulation in astrocytomas, including pilocytic and diffusely infiltrating astrocytomas. We examined 194 human gliomas and 23 normal brain white matter samples by immunohistochemistry or immunoblotting for AKAP12 expression. We further performed quantitative methylation analysis of the AKAP12 promoter by MassARRAY® of normal brain, World Health Organization (WHO) grade I to IV astrocytomas, and glioma cell lines. Our results show that AKAP12 is expressed in a perivascular distribution in normal CNS, strongly upregulated in tumor cells in pilocytic astrocytomas, and weakly expressed in diffuse astrocytomas of WHO grade II to IV. Methylation analyses revealed specific hypermethylation of AKAP12α promoter in WHO grade II to IV astrocytomas. Restoration experiments using 5-aza-2'-deoxycytidine in primary glioblastoma cells decreased AKAP12α promoter methylation and markedly increased AKAP12α mRNA levels. In summary, we demonstrate that AKAP12 is differentially expressed in human astrocytomas showing high expression in pilocytic but low expression in diffuse astrocytomas of all WHO-grades. Our results further indicate that epigenetic mechanisms are involved in silencing AKAP12 in diffuse astrocytomas; however, a tumor suppressive role of AKAP12 in distinct astrocytoma subtypes remains to be determined.
支架蛋白 A-激酶锚定蛋白 12（AKAP12）具有肿瘤抑制活性，在几种肿瘤实体中下调。我们研究了星形细胞瘤中 AKAP12 的表达和调节，包括毛细胞型和弥漫浸润性星形细胞瘤。我们通过免疫组化或免疫印迹法检查了 194 例人类脑胶质瘤和 23 例正常脑白质样本中 AKAP12 的表达。我们进一步通过 MassARRAY®对正常脑、世界卫生组织（WHO）I 级至 IV 级星形细胞瘤和神经胶质瘤细胞系进行 AKAP12 启动子的定量甲基化分析。我们的结果表明，AKAP12 在正常中枢神经系统中呈血管周围分布表达，在毛细胞型星形细胞瘤中的肿瘤细胞中强烈上调，在 WHO 分级 II 至 IV 的弥漫性星形细胞瘤中弱表达。甲基化分析显示，在 WHO 分级 II 至 IV 级星形细胞瘤中 AKAP12α 启动子存在特异性高甲基化。在原代神经胶质瘤细胞中使用 5-氮杂-2'-脱氧胞苷进行的恢复实验降低了 AKAP12α 启动子甲基化并显著增加了 AKAP12α mRNA 水平。总之，我们证明 AKAP12 在人类星形细胞瘤中表达不同，在毛细胞型星形细胞瘤中高表达，在所有 WHO 分级的弥漫性星形细胞瘤中低表达。我们的结果进一步表明，表观遗传机制参与了弥漫性星形细胞瘤中 AKAP12 的沉默；然而，AKAP12 在不同星形细胞瘤亚型中的肿瘤抑制作用仍有待确定。
