Kao Steven, Shaterian Ashkaun, Cauvi David M, Dang Xitong, Chun Hyun Bae, De Maio Antonio, Costantini Todd W, Coimbra Raul, Eliceiri Brian P, Baird Andrew
Department of Surgery Division of Trauma, Surgical Critical Care, Burn and Acute Care Surgery, School of Medicine, University of California in San Diego, La Jolla, California, USA.
Exp Lung Res. 2015 Apr;41(3):162-72. doi: 10.3109/01902148.2014.983282. Epub 2014 Dec 16.
The human c2orf40 gene encodes a candidate tumor suppressor called Esophageal Cancer-Related Gene-4 (ECRG4) that is a cytokine-like epigenetically-regulated protein that is characteristically downregulated in cancer, injury, inflammation, and infection. Here, we asked whether ECRG4 gene expression is detectable in lung epithelial cells and if its expression changes with inflammation, infection, and/or protective preconditioning.
We used immunoblotting, PCR, and quantitative PCR to measure ECRG4 and either inhalation anesthesia preconditioning, lipopolysaccharide injection, or laparotomy to modulate lung inflammation.
Immunoblotting establishes the presence of the full-length 14 kDa ECRG4 peptide in mouse lung. Immunohistochemistry localizes ECRG4 to type l alveolar epithelial cells. Basal ECRG4 mRNA is greater than TNF-α, IL-1β, and IL-6 but following inflammatory lung injury, TNF-α, IL-1β, IL-6, and IL-10 are upregulated while ECRG4 gene expression is decreased. Similar findings are observed after an intravenous administration of lipopolysaccharide. In contrast, lung preconditioning with isoflurane anesthesia increases lung ECRG4 gene expression. Over-expression of ECRG4 in human lung epithelial cells in vitro decreases cell proliferation implying that a loss of ECRG4 in vivo would be permissive to cell growth.
This study supports the hypothesis that ECRG4 acts as a sentinel growth inhibitor in lung alveolar epithelial cells. Its downregulation by injury, infection, and inflammation and upregulation by preconditioning supports a role for ECRG4 in regulating the alveolar epithelium response to injury and inflammation. By extension, the findings support a functional consequence to its inhibition by promoter hypermethylation (i.e. lung cancer) and suggest potential benefits to its upregulation.
人类c2orf40基因编码一种名为食管癌相关基因4（ECRG4）的候选肿瘤抑制因子，它是一种细胞因子样的表观遗传调控蛋白，在癌症、损伤、炎症和感染中通常下调。在此，我们探讨ECRG4基因表达在肺上皮细胞中是否可检测到，以及其表达是否会随炎症、感染和/或保护性预处理而发生变化。
我们使用免疫印迹、PCR和定量PCR来检测ECRG4，并通过吸入麻醉预处理、注射脂多糖或开腹手术来调节肺部炎症。
免疫印迹证实小鼠肺中存在全长14 kDa的ECRG4肽。免疫组化将ECRG4定位于I型肺泡上皮细胞。基础ECRG4 mRNA水平高于肿瘤坏死因子-α（TNF-α）、白细胞介素-1β（IL-1β）和白细胞介素-6（IL-6），但在肺部炎症损伤后，TNF-α、IL-1β、IL-6和白细胞介素-10（IL-10）上调，而ECRG4基因表达下降。静脉注射脂多糖后也观察到类似结果。相反，异氟烷麻醉预处理可增加肺ECRG4基因表达。体外在人肺上皮细胞中过表达ECRG4可降低细胞增殖，这意味着体内ECRG4缺失会促进细胞生长。
本研究支持以下假设，即ECRG4在肺泡上皮细胞中作为一种前哨生长抑制因子发挥作用。其因损伤、感染和炎症而下调，以及因预处理而上调，支持了ECRG4在调节肺泡上皮对损伤和炎症反应中的作用。由此推断，这些发现支持了其因启动子高甲基化而被抑制（即肺癌）所产生的功能后果，并提示了上调ECRG4的潜在益处。
