Open AccessHypoxia induces CD133 expression in human lung cancer cells by up-regulation of OCT3/4 and SOX2
Author(s) -
Hajime Iida,
Motoo Suzuki,
Ryo Goitsuka,
Hikaru Ueno
Publication year - 2011
Publication title -
international journal of oncology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.405
H-Index - 122
ISSN - 1019-6439
DOI - 10.3892/ijo.2011.1207
Subject(s) - biology , sox2 , promoter , chromatin immunoprecipitation , ectopic expression , gene knockdown , microbiology and biotechnology , transcription factor , transactivation , cancer research , regulation of gene expression , chromatin , gene expression , gene , genetics
CD133 has been recognized as a specific cell surface marker for cancer stemcells in various tumors, although its biological functions and transcriptionalregulation remain unclear. We found that the CD133 expression level was up-regulatedin the lung cancer cell lines N417, H358, and A549, when these cell lines werecultured under hypoxic conditions. Among the five promoters (P1-P5) of human CD133gene loci, P1 promoter was most strongly associated with hypoxia-induced promoteractivity of CD133 gene expression. The P1 promoter possesses several cis-regulatoryelements, including RUNT, GATA, ETS, OCT, SRY, and CREB-binding sites. A seriesof deletion and base substitution mutants of the P1 promoter revealed that OCT-and SRY-binding sites are important for hypoxia-induced promoter activity. Thechromatin immunoprecipitation assay further confirmed the direct binding of Octamerbiding trans-cription 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 ofboth OCT4 and SOX2 expression by the α subunit of hypoxia-inducible factors (HIF1αand HIF2α) was required for hypoxia-induced CD133 expression. Knockdown of OCT4or SOX2 expression in N417 cells with stabilized HIF1α and/or HIF2α abolishedCD133P1 activity, while ectopic OCT4 or SOX2 expression triggers CD133P1 activityin the absence of HIF1α or HIF2α. Thus, in the hypoxic conditions, OCT4 and SOX2,both of which are induced by HIF1α/HIF2α. promote CD133 expression in the lungcancer cells via their direct interaction with the P1 promoter.