Liu Na, Wang Yafang, Zhou Yongan, Pang Hailin, Zhou Jing, Qian Pei, Liu Lili, Zhang Helong
Department of Oncology, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
Department of Thoracic Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
Oncol Rep. 2014 Dec;32(6):2397-404. doi: 10.3892/or.2014.3495. Epub 2014 Sep 18.
Previously, we reported that hypoxia was able to induce invasion and metastasis in gastric cancer and that hypoxia-inducible factor-1 (HIF-1) is a key factor involved in this tumor type. Krüppel-like factor 8 (KLF8) as a transcriptional repressor has been suggested as a promoter of tumor metastasis in breast cancer and an inducer of the epithelial‑mesenchymal transition (EMT). KLF8 is also highly expressed in gastric cancer tissues, contributing to poor prognosis. However, the association between KLF8 and HIF-1 in regulating the progression of human gastric cancer in hypoxia is unclear. In the present study, we found that KLF8 was overexpressed in gastric cancer metastatic tissues and cells. Additionally, KLF8 siRNA significantly inhibited SGC7901 cell invasion and migration compared with SGC7901, SGC7901/Scr-si cells. Hypoxia is thus able to induce KLF8 expression and EMT in SGC7901 cells. However, following the examination of changes in cell morphology and epithelial and mesenchymal markers, it was found that KLF8 siRNA and HIF-1 siRNA strongly reversed EMT in cells undergoing hypoxia. Furthermore, hypoxia-induced KLF8 overexpression was attenuated by HIF-1 siRNA. Experiments using luciferase promoter constructs resulted in a marked increase in the activity of cells exposed to hypoxia and decreased activity in cells co-transfected with HIF-1 siRNA. The chromatin immunoprecipitation assay revealed proximal HRE at -133 is the main HIF-1 binding site in the KLF8 promoter. In conclusion, the results demonstrated that KLF8 is actively enhanced by hypoxia and is a novel HIF-1 target. KLF8 is a novel EMT regulating transcription factor that involved in the progression of gastric cancer. The specific anti-EMT drugs in combination with anti-hypoxia are new promising cancer therapies.
此前，我们报道过缺氧能够诱导胃癌的侵袭和转移，且缺氧诱导因子-1（HIF-1）是参与这种肿瘤类型的关键因素。Krüppel样因子8（KLF8）作为一种转录抑制因子，已被认为是乳腺癌肿瘤转移的促进因子和上皮-间质转化（EMT）的诱导因子。KLF8在胃癌组织中也高表达，与预后不良有关。然而，KLF8与HIF-1在缺氧条件下调节人类胃癌进展中的关联尚不清楚。在本研究中，我们发现KLF8在胃癌转移组织和细胞中过表达。此外，与SGC7901、SGC7901/Scr-si细胞相比，KLF8 siRNA显著抑制了SGC7901细胞的侵袭和迁移。因此，缺氧能够诱导SGC7901细胞中KLF8的表达和EMT。然而，在检查细胞形态以及上皮和间质标志物的变化后，发现KLF8 siRNA和HIF-1 siRNA强烈逆转了缺氧细胞中的EMT。此外，HIF-1 siRNA减弱了缺氧诱导的KLF8过表达。使用荧光素酶启动子构建体的实验导致暴露于缺氧条件下的细胞活性显著增加，而与HIF-1 siRNA共转染的细胞活性降低。染色质免疫沉淀试验显示，KLF8启动子中-133处的近端缺氧反应元件（HRE）是主要的HIF-1结合位点。总之，结果表明KLF8在缺氧条件下被积极增强，并且是一种新的HIF-1靶点。KLF8是一种参与胃癌进展的新型EMT调节转录因子。特异性抗EMT药物与抗缺氧药物联合使用是新的有前景的癌症治疗方法。
