Institute of Medicine, Chung-Shan Medical University, Taichung, Taiwan.
Division of Chest Medicine, Wuri Lin Shin Hospital, Taichung, Taiwan.
Toxicol Lett. 2021 Nov 1;352:17-25. doi: 10.1016/j.toxlet.2021.09.007. Epub 2021 Sep 24.
Angiopoietin-like protein 4 (ANGPTL4) is a hypoxia-induced gene, and its high expression is associated with poor prognosis and promotion of tumour progression in several cancers. Some studies reported that ANGPTL4 is affected by epigenetic regulation. Our previous results demonstrated that ANGPTL4 is highly expressed in most lung cancer cell lines than in normal cell lines and is upregulated by HIF-1α accumulation under NiCl exposure. The accurate role of ANGPTL4 and its methylation status caused by nickel in the lung carcinogenesis is not fully explored yet. In this study, we found that ANGPTL4 and HIF-1α in lung adenocarcinoma (LUAD) tissues were significantly upregulated compared with those in normal tissues in The Cancer Genome Atlas (TCGA) cohort (p < 0.001). The ANGPTL4 expression was statistically correlated to advanced stage (p = 0.019) and N value (p = 0.002). The Kaplan-Meier analysis revealed that ANGPTL4 and HIF-1α expression levels were independently associated with the 5-year survival of patients with LUAD in TCGA database and immunohistochemistry staining. In vitro experiments indicated that ANGPTL4 was upregulated by the demethylation agent. The methylation-specific PCR and bisulfite sequencing assessed the methylation status of the ANGPTL4 promoter, and results showed that NiCl-treated cells had low ANGPTL4 methylation status. We further demonstrated that the DNA demethylase, TET1, was significantly increased under NiCl exposure. The knockdown of TET1 expression repressed the NiCl-induced ANGPTL4. We also showed that nickel-induced TET1 was stimulated by HIF-1α. Our work established ANGPTL4 as a potential oncogene that contributes to lung cancer progression and nickel-elicited carcinogenesis.
血管生成素样蛋白 4（ANGPTL4）是一种缺氧诱导基因，其高表达与几种癌症中的不良预后和肿瘤进展有关。一些研究表明，ANGPTL4 受表观遗传调控的影响。我们之前的研究结果表明，ANGPTL4 在大多数肺癌细胞系中的表达高于正常细胞系，并且在 NiCl 暴露下 HIF-1α 积累时上调。ANGPTL4 的准确作用及其镍引起的甲基化状态在肺癌发生中的作用尚未完全探索。在这项研究中，我们发现，在癌症基因组图谱（TCGA）队列中，与正常组织相比，肺腺癌（LUAD）组织中的 ANGPTL4 和 HIF-1α 显著上调（p < 0.001）。ANGPTL4 的表达与晚期（p = 0.019）和 N 值（p = 0.002）呈统计学相关。Kaplan-Meier 分析表明，在 TCGA 数据库和免疫组织化学染色中，ANGPTL4 和 HIF-1α 的表达水平与 LUAD 患者的 5 年生存率独立相关。体外实验表明，去甲基化剂上调了 ANGPTL4 的表达。甲基化特异性 PCR 和亚硫酸氢盐测序评估了 ANGPTL4 启动子的甲基化状态，结果表明 NiCl 处理的细胞具有低的 ANGPTL4 甲基化状态。我们进一步证明，在 NiCl 暴露下，DNA 去甲基酶 TET1 显著增加。TET1 表达的敲低抑制了 NiCl 诱导的 ANGPTL4。我们还表明，镍诱导的 TET1 受 HIF-1α 刺激。我们的工作确立了 ANGPTL4 作为一种潜在的癌基因，有助于肺癌的进展和镍诱发的致癌作用。
