title: Regulation of aryl hydrocarbon receptor interacting protein (AIP) protein expression by MiR-34a in sporadic somatotropinomas.
abstract: BACKGROUND
  Patients with germline AIP mutations or low AIP protein expression have large, invasive somatotroph adenomas and poor response to somatostatin analogues (SSA).
  
  
  METHODS
  To study the mechanism of low AIP protein expression 31 sporadic somatotropinomas with low (n = 13) or high (n = 18) AIP protein expression were analyzed for expression of AIP messenger RNA (mRNA) and 11 microRNAs (miRNAs) predicted to bind the 3'UTR of AIP. Luciferase reporter assays of wild-type and deletion constructs of AIP-3'UTR were used to study the effect of the selected miRNAs in GH3 cells. Endogenous AIP protein and mRNA levels were measured after miRNA over- and underexpression in HEK293 and GH3 cells.
  
  
  RESULTS
  No significant difference was observed in AIP mRNA expression between tumors with low or high AIP protein expression suggesting post-transcriptional regulation. miR-34a was highly expressed in low AIP protein samples compared high AIP protein adenomas and miR-34a levels were inversely correlated with response to SSA therapy. miR-34a inhibited the luciferase-AIP-3'UTR construct, suggesting that miR-34a binds to AIP-3'UTR. Deletion mutants of the 3 different predicted binding sites in AIP-3'UTR identified the c.*6-30 site to be involved in miR-34a's activity. miR-34a overexpression in HEK293 and GH3 cells resulted in inhibition of endogenous AIP protein expression.
  
  
  CONCLUSIONS
  Low AIP protein expression is associated with high miR-34a expression. miR-34a can down-regulate AIP-protein but not RNA expression in vitro. miR-34a is a negative regulator of AIP-protein expression and could be responsible for the low AIP expression observed in somatotropinomas with an invasive phenotype and resistance to SSA.
authors: Department of Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom; Semmelweis University, School of PhD studies, Doctoral School of Clinical Medicine, Budapest, Hungary.
authors: Judit
authors: J
authors: Dénes
authors: Endocrinology Unit, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Leandro
authors: L
authors: Kasuki
authors: Department of Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom.
authors: Giampaolo
authors: G
authors: Trivellin
authors: Department of Internal Medicine, Endocrinology Laboratory, Ribeirão Preto Medical School, São Paulo University, São Paulo, Brazil.
authors: Leandro M
authors: LM
authors: Colli
authors: Biofísica Carlos Chagas Filho Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Christina M
authors: CM
authors: Takiya
authors: Department of Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom.
authors: Craig E
authors: CE
authors: Stiles
authors: Department of Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom.
authors: Sayka
authors: S
authors: Barry
authors: Department of Internal Medicine, Endocrinology Laboratory, Ribeirão Preto Medical School, São Paulo University, São Paulo, Brazil.
authors: Margaret
authors: M
authors: de Castro
authors: Endocrinology Unit, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Mônica R
authors: MR
authors: Gadelha
authors: Department of Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom.
authors: Márta
authors: M
authors: Korbonits
mesh_terms: D000328:Adult; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D049912:Growth Hormone-Secreting Pituitary Adenoma / Q000235:genetics / Q000473:pathology*; D057809:HEK293 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007633:Keratins / Q000378:metabolism; D008297:Male; D035683:MicroRNAs / Q000737:chemistry / Q000378:metabolism*; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D010911:Pituitary Neoplasms / Q000235:genetics / Q000473:pathology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D016415:Sequence Alignment
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; C103265:aryl hydrocarbon receptor-interacting protein; D007633:Keratins