title: Tissue factor-bearing microparticles derived from tumor cells: impact on coagulation activation.
abstract: BACKGROUND
  Tissue factor (TF)-bearing microparticles (MP) from different origins are thought to be involved in the pathogenesis of cancer-associated thrombosis. However, the role of circulating tumor cell-derived TF is not well understood.
  
  
  METHODS
  TF antigen and activity were measured in MP generated in vitro from human TF-expressing cancer cells by ELISA and clotting or thrombin generation assays, respectively. TF antigen and activity were also measured in vivo in cell-free plasmas from mice previously injected with in vitro-generated MP or in cell-free plasmas from nude mice bearing orthotopically injected human cancer cells.
  
  
  RESULTS
  Tumor cell-derived MP (TMP) exhibited strong TF-dependent procoagulant activity (PCA) in vitro and in vivo. Injection of TMP into mice was associated with acute thrombocytopenia and signs of shock, which were prevented by prior heparinization. Human TF antigen and activity could be detected in mouse cell-free plasmas up to 30 min after TMP injections. Human TF was detected in the spleen of injected mice and its clearance from circulation was delayed in splenectomized mice, suggesting the involvement of the spleen in the rapid clearance of circulating MP in vivo. Detectable levels of TF-dependent PCA and thrombin-antithrombin complex were found in cell-free plasmas from mice growing pancreatic human tumors, suggesting that circulating tumor-derived TF causes coagulation activation in vivo.
  
  
  CONCLUSIONS
  MP derived from certain cancer cells exhibit TF-dependent PCA both in vitro and in vivo. These results provide new information about the specific contribution of tumor-derived MP to the hypercoagulable state observed in cancer.
authors.affiliation: Institute of Translational Research, Florida Hospital, Orlando, FL, USA. monica.davila@flhosp.org
authors.forename: M
authors.initials: M
authors.lastname: Davila
authors.forename: A
authors.initials: A
authors.lastname: Amirkhosravi
authors.forename: E
authors.initials: E
authors.lastname: Coll
authors.forename: H
authors.initials: H
authors.lastname: Desai
authors.forename: L
authors.initials: L
authors.lastname: Robles
authors.forename: J
authors.initials: J
authors.lastname: Colon
authors.forename: C H
authors.initials: CH
authors.lastname: Baker
authors.forename: J L
authors.initials: JL
authors.lastname: Francis
mesh_terms: D000818:Animals; D001777:Blood Coagulation; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D004337:Drug Carriers; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008863:Microspheres; D013925:Thromboplastin / Q000008:administration & dosage* / Q000276:immunology
chemical_list: D004337:Drug Carriers; D013925:Thromboplastin