Li Chaojie, Yang Nannan, Chen Zhijin, Xia Ning, Shan Qungang, Wang Ziyin, Lu Jian, Shang Mingyi, Wang Zhongmin
Department of Radiology, Ruijin Hospital Luwan Branch, Shanghai Jiao Tong University School of Medicine, No. 149 Chongqing South Road, Shanghai, 200025, China.
Department of Interventional Radiology, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, 1111 Xianxia Road, Shanghai, 200336, China.
Cancer Cell Int. 2021 Jan 18;21(1):57. doi: 10.1186/s12935-020-01729-3.
Drug resistance and metastasis involving hypoxic tumor environments and persistent stem cell populations are detrimental to the survival of patients with non-small cell lung carcinoma (NSCLC). Tie1 is upregulated in hypoxia and is believed to counteract the effectiveness of platinum agents by promoting the stemness properties in cells. We have investigated the association of Tie1 with HIF-1α and cisplatin resistance in NSCLC cell lines.
The expression of Tie1 in a pulmonary microvascular endothelial cell line (HPMEC) and NSCLC cell lines was detected using qRT-PCR and western blotting. The effect of Tie1 on cell stemness and migration was examined by sphere-forming and transwell assays in NSCLC cells with Tie1 silenced. The regulation of Tie1 by HIF-1α was evaluated by a dual-luciferase reporter assay and chromatin immunoprecipitation.
We found that hypoxia could induce stemness and cisplatin resistance in vitro. Tie1 was expressed at low levels in NSCLC cells when compared with human pulmonary microvascular endothelial cells, however, its expression was increased by hypoxia. Additionally, Tie1 knockdown could reduce stemness properties and increase sensitivity to cisplatin in vitro and in a xenograft mouse model. The promoter of Tie1 contains two predicted hypoxia-response elements (HREs). We mutated both HRE sites and conducted chromatin immune-precipitation and promoter luciferase reporter assays and were able to conclude that the induction of Tie1 by hypoxia was HIF-1α-dependent.
Our findings indicated that Tie1 is upregulated in a hypoxic environment by HIF-1α and contributes to tumorigenesis and cisplatin resistance through the promotion of stemness in NSCLC cells.
涉及缺氧肿瘤环境和持续干细胞群体的耐药性和转移对非小细胞肺癌（NSCLC）患者的生存有害。Tie1在缺氧状态下上调，据信它通过促进细胞的干性特性来抵消铂类药物的有效性。我们研究了Tie1与NSCLC细胞系中HIF-1α和顺铂耐药性的关联。
使用qRT-PCR和蛋白质印迹法检测Tie1在肺微血管内皮细胞系（HPMEC）和NSCLC细胞系中的表达。通过对Tie1沉默的NSCLC细胞进行成球和Transwell实验，检测Tie1对细胞干性和迁移的影响。通过双荧光素酶报告基因检测和染色质免疫沉淀评估HIF-1α对Tie1的调控。
我们发现缺氧可在体外诱导干性和顺铂耐药性。与人类肺微血管内皮细胞相比，Tie1在NSCLC细胞中表达水平较低，然而，缺氧会增加其表达。此外，Tie1敲低可降低体外和异种移植小鼠模型中的干性特性并增加对顺铂的敏感性。Tie1的启动子包含两个预测的缺氧反应元件（HRE）。我们对两个HRE位点进行了突变，并进行了染色质免疫沉淀和启动子荧光素酶报告基因检测，能够得出缺氧诱导Tie1是HIF-1α依赖性的结论。
我们的研究结果表明，Tie1在缺氧环境中被HIF-1α上调，并通过促进NSCLC细胞的干性来促进肿瘤发生和顺铂耐药性。
