title: Exogenous SPARC suppresses proliferation and migration of prostate cancer by interacting with integrin β1.
abstract: BACKGROUND
  The matricellular protein secreted protein acidic and rich in cysteine (SPARC) plays an important role on tumor metastasis and progression in several cancers. However, the roles of SPARC in prostate cancer (PCa) remain unclear.
  
  
  METHODS
  To identify SPARC protein in prostate tissue, immunohistochemical analysis of SPARC was conducted using human prostate tissue microarray. To detect SPARC expression in prostate cancer (LNCaP, DU145, and PC-3) and stromal cells, RT-PCR, western blot analysis, and ELISA was conducted. To reveal the function of exogenous SPARC in PCa cells, AKT phosphorylation was confirmed by western blot analysis after coculture with stromal cells. Proliferation and migration of PCa cells were examined by addition of SPARC. The interaction between SPARC and integrin β1 was confirmed by western blot analysis after immunoprecipitation.
  
  
  RESULTS
  SPARC protein was expressed well in normal tissue compared with PCa tissue. ELISA showed high secreted SPARC protein in normal prostate-derived stromal cell (PrSC) compared with PCa-derived stromal cell (PCaSC) and PCa. PCa cells cocultured with PrSC showed reduced AKT phosphorylation more than with PCaSC. PCa cells cocultured with PrSC whose SPARC was knocked-down restored AKT phosphorylation. Moreover, PCa cells treated with SPARC led to reduced AKT phosphorylation. Immunoprecipitation with SPARC revealed interaction of SPARC and integrin β1 in PCa cells. Inhibited proliferation and migration of PCa cells by SPARC was restored by integrin β1 neutralizing antibody.
  
  
  CONCLUSIONS
  Reduced SPARC secretion from stromal cells might affect PCa progression mediating through limiting AKT phosphorylation after interaction with integrin β1.
authors.affiliation: Department of Integrative Cancer Therapy and Urology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Ishikawa, Japan.
authors.forename: Minkyoung
authors.initials: M
authors.lastname: Shin
authors.forename: Atsushi
authors.initials: A
authors.lastname: Mizokami
authors.forename: Jungim
authors.initials: J
authors.lastname: Kim
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ofude
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Konaka
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Kadono
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Kitagawa
authors.forename: Sotaro
authors.initials: S
authors.lastname: Miwa
authors.forename: Misako
authors.initials: M
authors.lastname: Kumaki
authors.forename: Evan T
authors.initials: ET
authors.lastname: Keller
authors.forename: Mikio
authors.initials: M
authors.lastname: Namiki
mesh_terms: D002464:Cell Migration Inhibition / Q000502:physiology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D018920:Coculture Techniques; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D008297:Male; D015676:Osteonectin; D011467:Prostate / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding / Q000502:physiology; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D019012:Integrin beta1; D015676:Osteonectin; C577241:SPARC protein, human; D025521:Tumor Suppressor Proteins