title: Six-transmembrane epithelial antigen of prostate 4 (STEAP4) is expressed on monocytes/neutrophils, and is regulated by TNF antagonist in patients with rheumatoid arthritis.
abstract: OBJECTIVE
  Human six-transmembrane epithelial antigen of prostate 4 (STEAP4) is one of the STEAP family as a homologue of mouse tumour necrosis factor-α-induced adipose-related protein (TIARP). Recently, we reported that the TIARP gene expression was remarkably increased in spleen and joints of glucose-6-phosphate isomerise (GPI)-induced arthritis model, suggesting pivotal association to arthritis. The aim of the present study was to assess the expression, localisation and function of STEAP4 in peripheral blood of patients with rheumatoid arthritis (RA).
  
  
  METHODS
  Peripheral blood was obtained from seven patients with RA, the surface expression of STEAP4 was detected by flow cytometry. The number of neutrophils was compared with the expression of STEAP4 mRNA derived from peripheral blood of patients with RA. Neutrophils were introduced by HL60 with retinoic acid, and were transfected with GFP-STEAP4 plasmid DNA, then the migration of neutrophil-like HL60 was determined by transwell assay. In addition, the fluctuation of STEAP4 mRNA was analysed before and after treatment with infliximab in 40 patients with RA.
  
  
  RESULTS
  STEAP4 was expressed on monocytes and neutrophils in peripheral blood in RA. The number of neutrophils and expression of STEAP4 mRNA was positively correlated. Migration of neutrophil-like HL60 was down-regulated by over-expression of STEAP4. Expression of STEAP4 Mrna was significantly decreased after infliximab treatment in patients with RA, especially in good responders.
  
  
  CONCLUSIONS
  STEAP4 is expressed on monocytes and neutrophils in peripheral blood, regulates cell migration, is down-regulated by TNF antagonist, and might be a possible predictor of response to TNF antagonist.
authors.affiliation: Division of Clinical Immunology, Doctoral Programme in Clinical Science, Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: I
authors.initials: I
authors.lastname: Matsumoto
authors.forename: K
authors.initials: K
authors.lastname: Iwanami
authors.forename: A
authors.initials: A
authors.lastname: Inoue
authors.forename: N
authors.initials: N
authors.lastname: Umeda
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Sugihara
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
authors.forename: S
authors.initials: S
authors.lastname: Ito
authors.forename: T
authors.initials: T
authors.lastname: Sumida
mesh_terms: D000328:Adult; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use; D018501:Antirheumatic Agents / Q000494:pharmacology / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D000069285:Infliximab; D008565:Membrane Proteins / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors
chemical_list: D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D008565:Membrane Proteins; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D010088:Oxidoreductases; C503310:STEAP4 protein, human