Department of Ophthalmology, University of Bonn, Ernst-Abbe-Str. 2, 53127, Bonn, Germany.
Institute of Medical Biometry, Informatics and Epidemiology (IMBIE), University of Bonn, Sigmund-Freud-Str. 25, 53127, Bonn, Germany.
Exp Eye Res. 2019 May;182:175-181. doi: 10.1016/j.exer.2019.04.001. Epub 2019 Apr 4.
Cancer evolves from a combination of genetic and epigenetic abnormalities resulting in aberrant gene expression profiles as well as altered epigenomic patterns. Epigenetic alterations such as DNA methylation and histone modification play an important role in tumorigenesis. While in the pathobiology of uveal melanoma (UM) genetic changes have been well characterized, there is growing evidence suggesting that epigenetic changes are also involved. We investigated whether epigenetic modifications (global levels of histone acetylation, DNA methylation, ubiquitination) are detectable in UM tissues compared to healthy controls with respect to inter- and intratumoral heterogeneity. Formalin-fixed paraffin-embedded tissues of primary UM (n = 15), UM metastasis (n = 13), and control choroid (n = 12) were immunohistochemically investigated by two ophthalmic pathologists for global levels of histone acetylation (Histone 3 acetylation, H3Ac; Histone 4 acetylation, H4Ac), DNA methylation (5-methylcytosine, 5-MeC; 5'-hydroxymethylcytosine, 5-hMeC), global ubiquitination (UBC) as well as Ubiquityl-Histone H2A (H2Aub). The nuclear staining intensity of primary tumors, metastases and control choroids was evaluated using a score from 0 to 3, which was multiplied with the percentage of stained cells (score from 0 to 4). The control choroid and the choroid next to the tumor showed a more intense nuclear staining than the primary tumor tissue. The choroid next to the tumor was stained less than the control choroid. The nuclear staining intensity in the tumor was comparable to that in the metastases. The tumor tissue itself often exhibited a heterogeneous staining pattern, as nuclei in the tumor center were less intensely stained than in the periphery. Cells with a presumed invasive potential (extraocular extension, growth along emissary canals) showed also an intense staining reaction. Although no prognostically relevant pattern of global epigentic markers could be identified, our results suggest that epigenetic changes play a role in UM pathogenesis and metastasis. In particular the staining reaction of tumor cell subtypes with a presumed invasive potential warrants further attention. The role of epigenetically relevant interactions with the tumor micromilieu should be further investigated as immune cells are predominantly located in the tumor periphery which showed a different staining intensity than the tumor center. However, as considerable epigenetic diversity exists in primary tumors, studies on biopsy tissue are not recommended for the immunohistochemical investigation of epigenetic markers.
癌症是由遗传和表观遗传异常共同导致的，这些异常导致基因表达谱异常和表观基因组模式改变。表观遗传改变，如 DNA 甲基化和组蛋白修饰，在肿瘤发生中发挥重要作用。虽然葡萄膜黑色素瘤（UM）的病理生物学中已经很好地描述了遗传变化，但越来越多的证据表明，表观遗传变化也参与其中。我们研究了与肿瘤内和肿瘤间异质性相比，UM 组织中是否存在可检测的表观遗传修饰（组蛋白乙酰化、DNA 甲基化、泛素化的整体水平）。两位眼科病理学家通过免疫组织化学方法，对原发性 UM（n=15）、UM 转移（n=13）和对照脉络膜（n=12）的福尔马林固定石蜡包埋组织进行了研究，以检测组蛋白乙酰化（组蛋白 3 乙酰化，H3Ac；组蛋白 4 乙酰化，H4Ac）、DNA 甲基化（5-甲基胞嘧啶，5-MeC；5-羟甲基胞嘧啶，5-hMeC）、泛素化（UBC）和泛素化组蛋白 H2A（H2Aub）的整体水平。使用 0 到 3 的评分乘以染色细胞的百分比（评分从 0 到 4）来评估原发性肿瘤、转移灶和对照脉络膜的核染色强度。与肿瘤相邻的脉络膜和对照脉络膜的核染色强度强于原发性肿瘤组织。与对照脉络膜相比，与肿瘤相邻的脉络膜染色较少。肿瘤组织本身通常表现出异质性染色模式，因为肿瘤中心的核染色强度低于肿瘤周围。具有推定侵袭潜能的细胞（眼外扩展，沿导血管生长）也表现出强烈的染色反应。虽然没有发现具有预后意义的整体表观遗传标记模式，但我们的结果表明，表观遗传变化在 UM 发病机制和转移中发挥作用。特别是具有推定侵袭潜能的肿瘤细胞亚型的染色反应值得进一步关注。与肿瘤微环境的表观遗传相关相互作用的作用应进一步研究，因为免疫细胞主要位于肿瘤周围，其染色强度与肿瘤中心不同。然而，由于原发性肿瘤中存在相当大的表观遗传多样性，因此不建议对活检组织进行免疫组织化学研究以检测表观遗传标记。
