Canine malignant melanoma is a common cancer with a high mortality rate and is a clinically important disease. DNA methylation has been considered to be a potential tumorigenic mechanism through aberrant DNA methylation at promoter region which represses gene transcription. Global hypomethylation could also facilitate chromosome instability. There are few reports regarding DNA methylation in canine malignant melanoma; therefore, the purpose of this study was to examine DNA methylation status of long interspersed nucleotide element‐1 (LINE‐1) to be a surrogate marker of genome‐wide methylation changes in this disease. We measured levels of DNA methylation of two adjacent cytosine‐guanine sites on CpG island (CGI) at the putative promoter of canine LINE‐1 sequence by bisulphite‐pyrosequencing in 41 canine melanoma patient samples as well as six cell lines compared with normal mucosae. The survival rates were obtained from owners or medical records. We found DNA methylation levels of LINE‐1 in normal mucosae were methylated. Interestingly, both melanoma cell lines and clinical melanoma samples showed remarkable hypomethylation. In addition, patients with lower LINE‐1 methylation showed worse prognosis than those with higher LINE‐1 methylation, though the difference did not reach statistical significance (P = .09). Here, we demonstrate that hypomethylation of LINE‐1 is an epigenetically aberrant feature in canine melanoma with possible prognostic value.

中文翻译：

---

犬恶性粘膜黑色素瘤中的长散布核苷酸元件-1低甲基化


犬恶性黑色素瘤是一种常见的癌症，死亡率较高，是临床上的重要疾病。 DNA甲基化被认为是一种潜在的致瘤机制，通过启动子区域的异常DNA甲基化抑制基因转录。整体低甲基化也可能促进染色体不稳定。关于犬恶性黑色素瘤DNA甲基化的报道很少；因此，本研究的目的是检查长散布核苷酸元件 1 (LINE-1) 的 DNA 甲基化状态，以作为该疾病全基因组甲基化变化的替代标记。我们通过亚硫酸氢盐焦磷酸测序在 41 例犬黑色素瘤患者样本以及 6 个细胞系中与正常粘膜进行比较，测量了犬 LINE-1 序列推定启动子处 CpG 岛 (CGI) 上两个相邻胞嘧啶-鸟嘌呤位点的 DNA 甲基化水平。存活率是从所有者或医疗记录中获得的。我们发现正常粘膜中 LINE-1 的 DNA 甲基化水平是甲基化的。有趣的是，黑色素瘤细胞系和临床黑色素瘤样本均显示出显着的低甲基化。此外，LINE-1 甲基化程度较低的患者比 LINE-1 甲基化程度较高的患者预后更差，但差异并未达到统计学显着性 ( P = .09)。在这里，我们证明 LINE-1 的低甲基化是犬黑色素瘤的表观遗传异常特征，具有可能的预后价值。