Liang Jie, Bai Feihu, Luo Guanhong, Wang Jingbo, Liu Jingmei, Ge Fulin, Pan Yanglin, Yao Liping, Du Rui, Li Xiaohua, Fan Rui, Zhang Hongbo, Guo Xuegang, Wu Kaichun, Fan Daiming
State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
Cancer Biol Ther. 2007 May;6(5):769-74. doi: 10.4161/cbt.6.5.4001. Epub 2007 Feb 12.
Cellular prion protein (PrP(C)), a copper-binding glycosyl-phosphatidylinositol (GPI)-anchored membrane protein that is expressed predominantly in neurons can be induced in ischemia/hypoxic brain tissues. It was also found to be overexpressed and conferred multidrug resistance, promoting cancer metastasis and inhibiting apoptosis in gastric cancer in our lab. In solid tumors, hypoxia can promote malignant progression and confer resistance to chemotherapy by altering gene expression. In present study, we investigated the molecular mechanisms and signaling pathway involved in the induction of the PrP(C) gene by hypoxia in cancer cell lines. PrP(C) was detected to be upregulated in several cancer cell lines at both mRNA and protein level, and then found to be induced by hypoxia in a time-dependent manner. After hypoxia treatment, gastric cancer MKN28 cells transfected with luciferase reporter constructs of the human PrP(C) promoter, which contained HSE, expressed higher luciferase activities (4.3-fold) than those cells transfected with the constructs containing no HSE. In addition, the upregulation of PrP(C) was reduced by MERK/ERK inhibitor (PD98059). siRNA knockdown of PrP(C) could make the cells more sensitive to hypoxia induced drug sensitivity. In conclusion, from these findings, we can propose that some transcriptional factors phosphorylated by ERK1/2, could in turn interact with HSE in the promoter of PrP(C) resulting in upregulation of PrP(C) in gastric cancer cell line MKN28 during hypoxia. Downregulation of PrP(C) makes gastric cancer cells more sensitive to hypoxia induced drug sensitivity. However, other mechanisms might also be responsible for hypoxia induced overexpression of PrP(C) in gastric cancer.
细胞朊蛋白（PrP(C)）是一种主要在神经元中表达的铜结合糖基磷脂酰肌醇（GPI）锚定膜蛋白，可在缺血/缺氧脑组织中被诱导产生。在我们实验室还发现它在胃癌中过表达并赋予多药耐药性，促进癌症转移并抑制细胞凋亡。在实体瘤中，缺氧可通过改变基因表达促进恶性进展并赋予化疗耐药性。在本研究中，我们调查了癌细胞系中缺氧诱导PrP(C)基因表达的分子机制和信号通路。检测发现PrP(C)在几种癌细胞系的mRNA和蛋白水平均上调，且发现其受缺氧诱导呈时间依赖性。缺氧处理后，转染了含热休克元件（HSE）的人PrP(C)启动子荧光素酶报告基因构建体的胃癌MKN28细胞，其荧光素酶活性（4.3倍）高于转染不含HSE构建体的细胞。此外，PrP(C)的上调被丝裂原活化蛋白激酶/细胞外信号调节激酶（MERK/ERK）抑制剂（PD98059）所抑制。PrP(C)的小干扰RNA（siRNA）敲低可使细胞对缺氧诱导的药物敏感性增加。总之，从这些发现中我们可以推测，一些被ERK1/2磷酸化的转录因子可能反过来与PrP(C)启动子中的HSE相互作用，导致胃癌细胞系MKN28在缺氧时PrP(C)上调。PrP(C)的下调使胃癌细胞对缺氧诱导的药物敏感性增加。然而，其他机制可能也与胃癌中缺氧诱导的PrP(C)过表达有关。
