Hypoxia induces CD133 expression in human lung cancer cells by up-regulation of OCT3/4 and SOX2
Hypoxia induces CD133 expression in human lung cancer cells by up-regulation of OCT3/4 and SOX2
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DOI：
10.3892/ijo.2011.1207
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发表时间：
2012-01-01
影响因子：
5.2
通讯作者：
Ueno, Hikaru
中科院分区：
文献类型：
--
作者：
Iida, Hajime;Suzuki, Mitsuhiro;Ueno, Hikaru
CD133已被认为是多种肿瘤中癌症干细胞的特异性细胞表面标志物，尽管其生物学功能和转录调控尚不清楚。我们发现在缺氧条件下培养的肺癌细胞系N417、H358和A549中CD133的表达水平上调。在人类CD133基因位点的5个启动子（P1-P5）中。P1启动子与缺氧诱导的CD133基因表达启动子活性相关性最强。P1启动子具有几个顺式调控元件，包括RUNT、GATA、ETS、OCT、SRY和creb结合位点。P1启动子的一系列缺失和碱基替换突变表明，OCT-和sry结合位点对缺氧诱导的启动子活性很重要。染色质免疫沉淀实验进一步证实了Octamer binding transcription factor 3/4 （OCT4）和/或SRY-box containing gene 2 （SOX2）与CD133基因位点P1启动子区直接结合。此外，缺氧诱导因子α亚基（HIF1 α和HIF2 α）对OCT4和SOX2表达的增强是缺氧诱导CD133表达的必要条件。在HIF1 α和/或HIF2 α稳定的N417细胞中，敲低OCT4或SOX2表达可消除CD133P1活性，而在HIF1 α或HIF2 α缺失的情况下，OCT4或SOX2异位表达可触发CD133P1活性。因此，在缺氧条件下，由HIF1 α /HIF2 α诱导的OCT4和SOX2通过与P1启动子的直接相互作用促进CD133在肺癌细胞中的表达。
CD133 has been recognized as a specific cell surface marker for cancer stem cells in various tumors, although its biological functions and transcriptional regulation remain unclear. We found that the CD133 expression level was up-regulated in the lung cancer cell lines N417, H358, and A549, when these cell lines were cultured under hypoxic conditions. Among the five promoters (P1-P5) of human CD133 gene loci. P1 promoter was most strongly associated with hypoxia-induced promoter activity of CD133 gene expression. The P1 promoter possesses several cis-regulatory elements, including RUNT, GATA, ETS, OCT, SRY, and CREB-binding sites. A series of deletion and base substitution mutants of the P1 promoter revealed that OCT- and SRY-binding sites are important for hypoxia-induced promoter activity. The chromatin immunoprecipitation assay further confirmed the direct binding of Octamer biding transcription factor 3/4 (OCT4) and/or SRY-box containing gene 2 (SOX2) to the P1 promoter region of CD133 gene loci. In addition, the enhancement of both OCT4 and SOX2 expression by the alpha subunit of hypoxia-inducible factors (HIF1 alpha and HIF2 alpha) was required for hypoxia-induced CD133 expression. Knockdown of OCT4 or SOX2 expression in N417 cells with stabilized HIF1 alpha and/or HIF2 alpha abolished CD133P1 activity, while ectopic OCT4 or SOX2 expression triggers CD133P1 activity in the absence of HIF1 alpha or HIF2 alpha. Thus, in the hypoxic conditions, OCT4 and SOX2, both of which are induced by HIF1 alpha/HIF2 alpha promote CD133 expression in the lung cancer cells via their direct interaction with the P1 promoter.