title: Expression and regulation of retinoid-inducible gene 1 (RIG1) in breast cancer.
abstract: BACKGROUND
  Retinoid-inducible gene I (RIG1) is a growth regulator protein that exhibits activities to suppress cellular growth and induce cellular differentiation and apoptosis. This study analyzed the expression and regulation of RIG1 in breast cancer cells in vitro and in vivo.
  
  
  METHODS
  Expression of RIG1 RNA in breast cancer tissues was analyzed using RNA in situ hybridization. Regulation of RIG1 expression by 17beta-estradiol (E2) was analyzed by semi-quantitative reverse transcription polymerase chain reaction.
  
  
  RESULTS
  RIG1 expression in 47 breast cancer tissues was detected mostly in the cytoplasm and in some nuclei. Levels of both cytoplasmic and nuclear RIG1 mRNA were significantly lower in 20 estrogen receptor-positive (ER+) than in 27 ER-negative (ER-) tissues (p < 0.05), in 20 progesterone receptor-positive (PR+) than in 27 PR-negative (PR-) tissues (p < 0.01), and in 14 ER+/PR+ than in 21 ER-/PR-tissues (p < 0.05). Basal levels of RIG1 and ER mRNA were inversely related between ER+ (MCF-7 WS8 and ZR75-1) and ER- (ZR-75-30) breast cancer cells. E2 (1 nM) treatment for two days suppressed RIG1 mRNA levels in MCF-7 WS8 and ZR-75-1 cells, but not in the ER- ZR-75-30 cells. The E2-mediated down-regulation of RIG1 expression was time- and concentration-dependent in ZR-75-1 cells.
  
  
  CONCLUSIONS
  The negative association between RIG1 and ER expression in breast cancer tissues and down-regulation of RIG1 by E2 in breast cancer cells in vitro suggest that RIG1 expression is negatively regulated by E2 through activation of the ER in ER+ breast cancer cells.
authors.affiliation: Department of Internal Medicine, Tri-Service General Hospital, No. 325, Chengung Road, Sec 2, Taipei, Taiwan, Republic of China.
authors.forename: Rong-Yaun
authors.initials: RY
authors.lastname: Shyu
authors.forename: Show-Cheng
authors.initials: SC
authors.lastname: Chang
authors.forename: Jyh-Cherng
authors.initials: JC
authors.lastname: Yu
authors.forename: Shih-Jui
authors.initials: SJ
authors.lastname: Hsu
authors.forename: Jung-Mao
authors.initials: JM
authors.lastname: Chou
authors.forename: Meei-Shyuan
authors.initials: MS
authors.lastname: Lee
authors.forename: Shun-Yuan
authors.initials: SY
authors.lastname: Jiang
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D000077267:Fulvestrant; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D017403:In Situ Hybridization; D009367:Neoplasm Staging; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000235:genetics; D011980:Receptors, Progesterone / Q000096:biosynthesis / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C437968:PLAAT4 protein, human; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D018168:Receptors, Retinoic Acid; D000077267:Fulvestrant; D004958:Estradiol