title: Down-regulation of NDRG1 promotes migration of cancer cells during reoxygenation.
abstract: One characteristic of tumor microenvironment is oxygen fluctuation, which results from hyper-proliferation and abnormal metabolism of tumor cells as well as disorganized neo-vasculature. Reoxygenation of tumors can induce oxidative stress, which leads to DNA damage and genomic instability. Although the cellular responses to hypoxia are well known, little is known about the dynamic response upon reoxygenation. In order to investigate the transcriptional responses of tumor adaptation to reoxygenation, breast cancer MCF-7 cells were cultured under 0.5% oxygen for 24 h followed by 24 h of reoxygenation in normoxia. Cells were harvested at 0, 1, 4, 8, 12, and 24 h during reoxygenation. The transcriptional profile of MCF-7 cells upon reoxygenation was examined using Illumina Human-6 v3 BeadChips. We identified 127 differentially expressed genes, of which 53.1% were up-regulated and 46.9% were down-regulated upon reoxygenation. Pathway analysis revealed that the HIF-1-alpha transcription factor network and validated targets of C-MYC transcriptional activation were significantly enriched in these differentially expressed genes. Among these genes, a subset of interest genes was further validated by quantitative reverse-transcription PCR. In particular, human N-MYC down-regulated gene 1 (NDRG1) was highly suppressed upon reoxygenation. NDRG1 is associated with a variety of stress and cell growth-regulatory conditions. To determine whether NDRG1 plays a role in reoxygenation, NDRG1 protein was overexpressed in MCF-7 cells. Upon reoxygenation, overexpression of NDRG1 significantly inhibited cell migration. Our results revealed the dynamic nature of gene expression in MCF-7 cells upon reoxygenation and demonstrated that NDRG1 is involved in tumor adaptation to reoxygenation.
authors.affiliation: Graduate Institute of Physiology, National Taiwan University, Taipei, Taiwan.
authors.forename: Liang-Chuan
authors.initials: LC
authors.lastname: Lai
authors.forename: Yi-Yu
authors.initials: YY
authors.lastname: Su
authors.forename: Kuo-Chih
authors.initials: KC
authors.lastname: Chen
authors.forename: Mong-Hsun
authors.initials: MH
authors.lastname: Tsai
authors.forename: Yuh-Pyng
authors.initials: YP
authors.lastname: Sher
authors.forename: Tzu-Pin
authors.initials: TP
authors.lastname: Lu
authors.forename: Chien-Yueh
authors.initials: CY
authors.lastname: Lee
authors.forename: Eric Y
authors.initials: EY
authors.lastname: Chuang
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018797:Cell Cycle Proteins / Q000235:genetics*; D015687:Cell Hypoxia / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics*; D019295:Computational Biology; D015536:Down-Regulation / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010100:Oxygen / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D000099259:N-myc Downstream-Regulated Gene 1 Protein
chemical_list: D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D035683:MicroRNAs; D010100:Oxygen; D016271:Proto-Oncogene Proteins c-myc; D014157:Transcription Factors; D000099259:N-myc Downstream-Regulated Gene 1 Protein