title: Elevated numbers and altered subsets of procoagulant microparticles in breast cancer patients using endocrine therapy.
abstract: BACKGROUND
  Microparticles (MP) can be elevated in cancer and thromboembolic disease. We hypothesized a role for MP in the hypercoagulable state in breast cancer patients using endocrine therapy, in whom both cancer and the use of endocrine therapy are independent risk factors for the development of thrombosis.
  
  
  METHODS
  Plasma samples were collected from 40 breast cancer patients using endocrine therapy (20 patients without metastases receiving adjuvant therapy and 20 patients with metastatic disease treated in a palliative setting) and from 20 female healthy controls. The endocrine therapy used was either an anti-estrogen or an aromatase inhibitor. Numbers and cellular origin of MP subsets were analyzed by flowcytometry. MP-associated procoagulant activity was measured using a thrombin generation assay using conditions that allow analysis of MP induced thrombin generation.
  
  
  RESULTS
  Breast cancer patients using endocrine therapy had higher levels of MP positive for Annexin V (median 10000 vs 6500×10E6/l), P-selectin (330 vs 200×10E6/l), tissue factor (33 vs 15×10E6/l), and of MP derived from platelets (CD41) and leukocytes (CD45). Thrombin generation in plasma was dependent on the presence of MP and thrombin generation performed after addition of isolated MP to normal plasma showed a higher endogenous thrombin potential (1105 vs 1029 nM.min) in breast cancer patients. No differences were observed in MP levels and thrombin generation parameters between the metastatic and adjuvant group.
  
  
  CONCLUSIONS
  Breast cancer patients using endocrine therapy have an increased MP number and a higher MP-dependent thrombin generation, irrespective of the presence of metastatic disease. Altered MP subset characteristics in these patients, especially the higher number of (activated) platelet derived MP and leukocyte derived MP, may in part explain a heightened procoagulant state in breast cancer patients using endocrine therapy.
authors.affiliation: Department of Internal Medicine, Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands. mctrappenburg@gmail.com
authors.forename: Marijke C
authors.initials: MC
authors.lastname: Trappenburg
authors.forename: Muriel
authors.initials: M
authors.lastname: van Schilfgaarde
authors.forename: Edwin O
authors.initials: EO
authors.lastname: Bredewold
authors.forename: Michiel C
authors.initials: MC
authors.lastname: van Aalderen
authors.forename: Henri M H
authors.initials: HM
authors.lastname: Spronk
authors.forename: Hugo
authors.initials: H
authors.lastname: Ten Cate
authors.forename: Anja
authors.initials: A
authors.lastname: Leyte
authors.forename: Wim E
authors.initials: WE
authors.lastname: Terpstra
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000009:adverse effects*; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000150:complications* / Q000188:drug therapy* / Q000473:pathology / Q000556:secondary; D055252:Cell-Derived Microparticles / Q000473:pathology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D013917:Thrombin / Q000378:metabolism; D013927:Thrombosis / Q000209:etiology* / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D013917:Thrombin