title: Epigenetic silencing of NDRG2 promotes colorectal cancer proliferation and invasion.
abstract: BACKGROUND
  Genome-wide methylation arrays have revealed aberrant methylation of N-Myc downstream-regulated gene 2 (NDRG2) promoter in colorectal cancer (CRC). This study investigated the role of NDRG2 in colorectal carcinogenesis.
  
  
  METHODS
  The aberrant promoter methylation, mRNA, and protein expression of NDRG2 were evaluated in 27 pairs of human CRC and adjacent normal tissues and seven human CRC-derived cell-lines. After stable NDRG2 over-expressed RKO and DLD-1 human CRC cell-lines were constructed, in vitro functional assays, including colony formation, cell viability, proliferation, invasion and migration assays, and in vivo xenograft models were performed.
  
  
  RESULTS
  The promoter of NDRG2 was methylated in 89% human CRC tissue compared to adjacent normal colonic mucosa (7.4%; P < 0.001). High-level methylation of NDRG2 promoter was more prevalent in proximal CRC (P = 0.022) and advanced T stage (P = 0.039). NDRG2 mRNA and protein expression was down-regulated in 89% and 100% human CRC tissue, respectively. In human CRC cell-lines, the promoter of NDRG2 was methylated aberrantly and mRNA, and protein expression of NDRG2 was down-regulated. NDRG2 mRNA expression was reactivated by 5-aza-2'-deoxycytidine. Colony formation of NDRG2 over-expressing RKO cells was inhibited (P = 0.012), as was the viability, proliferation, and invasion of NDRG2 over-expressing DLD-1 cells (P < 0.001, P = 0.003, and P = 0.044, respectively). Tumor volume in xenograft mice transplanted with NDRG2 over-expressing RKO and DLD-1 cells was smaller than that in controls (P = 0.002 and P = 0.001, respectively).
  
  
  CONCLUSIONS
  Epigenetic silencing of NDRG2 induces proliferation and invasion of CRC and may be associated with proximal CRC and advanced T stage. NDRG2 methylation might serve as novel biomarker of CRC.
authors.affiliation: Department of Medicine, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Sung Noh
authors.initials: SN
authors.lastname: Hong
authors.affiliation: Samsung Biomedical Research Institute, Samsung Medical Center, Seoul, Republic of Korea.
authors.forename: Sung Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Medicine, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Eun-Ran
authors.initials: ER
authors.lastname: Kim
authors.affiliation: Department of Medicine, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Dong Kyung
authors.initials: DK
authors.lastname: Chang
authors.affiliation: Department of Medicine, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D015870:Gene Expression; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008807:Mice, Inbred BALB C; D009361:Neoplasm Invasiveness / Q000235:genetics; D009367:Neoplasm Staging; D009368:Neoplasm Transplantation; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: C466228:NDRG2 protein, human; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins
keywords: N-Myc downstream-regulated gene 2; colorectal cancers; methylation; tumor suppressor gene