title: Prothrombotic effect of prostasomes of metastatic cell and seminal origin.
abstract: BACKGROUND
  Prostasomes are secretory granules produced by the glandular epithelial cells of the prostate. Seminal prostasomes contain high amounts of Tissue Factor (TF) but no studies of TF on malignant cell prostasomes have been made. Here we compare the expression, phosphorylation, and function of TF on prostasomes of different origin.
  
  
  METHODS
  TF was detected on prostasomes isolated from seminal fluid and human prostate cancer cell lines (PC-3, DU145, and LNCaP) using FACS and enzyme immunoassay (EIA). Incubation of prostasomes with radioactive ATP under conditions favoring protein kinase A activity led to phosphorylation of TF as detected by immunoprecipitation and SDS-PAGE. The prothrombotic effect of prostasomes was investigated in whole blood and recalcified plasma. Blocking experiments were performed using anti-TF antibodies and corn trypsin inhibitor.
  
  
  RESULTS
  TF was expressed on all tested prostasome preparations with lowest values found for seminal ones. Prostasomal TF was the main endogenous substrate for prostasomal protein kinase A. All tested prostasome preparations greatly enhanced the rate of clot formation in a dose-dependent fashion, that is, the clotting capability of prostasomes seemed to be related to the extent of their expression of TF. In addition, the density of the clot varied between different prostasome preparations. When incubated in whole blood, prostasomes were found to associate to WBC thereby inducing them to express and release TF.
  
  
  CONCLUSIONS
  These data show that TF is overexpressed and also subjected to phosphorylation by malignant cell prostasomes. This suggests major roles for prostasomes in thrombotic events that occur in some advanced cases of prostate cancer.
authors.affiliation: Department of Oncology, Radiology, and Clinical Immunology, Division of Clinical Immunology, Rudbeck Laboratory C5, Uppsala, Sweden.
authors.forename: Adil A
authors.initials: AA
authors.lastname: Babiker
authors.forename: Osama A
authors.initials: OA
authors.lastname: Hamad
authors.forename: Javier
authors.initials: J
authors.lastname: Sanchez
authors.forename: Gunnar
authors.initials: G
authors.lastname: Ronquist
authors.forename: Bo
authors.initials: B
authors.lastname: Nilsson
authors.forename: Kristina Nilsson
authors.initials: KN
authors.lastname: Ekdahl
mesh_terms: D002118:Calcium / Q000097:blood; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D009391:Nephelometry and Turbidimetry; D010766:Phosphorylation; D011467:Prostate / Q000378:metabolism / Q000473:pathology; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000556:secondary*; D011494:Protein Kinases / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism / Q000473:pathology*; D012670:Seminiferous Epithelium / Q000378:metabolism / Q000473:pathology; D013925:Thromboplastin / Q000378:metabolism; D013927:Thrombosis / Q000209:etiology* / Q000378:metabolism / Q000473:pathology*
chemical_list: D013925:Thromboplastin; D011494:Protein Kinases; D002118:Calcium