title: Elucidation of flow-mediated tumour cell-induced platelet aggregation using an ultrasound standing wave trap.
abstract: OBJECTIVE
  Tumour cells activate and aggregate platelets [tumour cell-induced platelet aggregation (TCIPA)] and this process plays an important role in the successful metastasis of cancer cells. To date, most studies on TCIPA have been conducted under no-flow conditions. In this study, we have investigated TCIPA in real time under flow conditions, using an ultrasound standing wave trap that allows formation and levitation of cancer cell clusters in suspension, thus mimicking the conditions generated by flowing blood.
  
  
  METHODS
  Using 59M adenocarcinoma and HT1080 fibrosarcoma cells and human platelets, cancer cell cluster-platelet aggregates were imaged in real time using epi-fluorescence microscopy (F-actin) and investigated in detail using confocal microscopy (matrix metalloproteinase-2-GPIIb/IIIa co-localization) and scanning electron and helium-ion microscopy (<1 nm resolution). The release of gelatinases from aggregates was studied using zymography.
  
  
  RESULTS
  We found that platelet activation and aggregation takes place on the surface of cancer cells (TCIPA), leading to time-dependent disruption of cancer cell clusters. Pharmacological modulation of TCIPA revealed that EDTA, prostacyclin, o-phenanthroline and apyrase significantly down-regulated TCIPA and, in turn, delayed cell cluster disruption, However, EGTA and aspirin were ineffective. Pharmacological inhibition of TCIPA correlated with the down-regulation of platelet activation as shown by flow-cytometry assay of platelet P-selectin.
  
  
  CONCLUSIONS
  Our results show for the first time, that during TCIPA, platelet activation disrupts cancer cell clusters and this can contribute to metastasis. Thus, selective targeting of platelet aggregate-cancer cell clusters may be an important strategy to control metastasis.
authors.affiliation: Centre for Research on Adaptive Nanostructures and Nanodevices, Trinity College Dublin, Dublin, Ireland.
authors.forename: D
authors.initials: D
authors.lastname: Bazou
authors.forename: M J
authors.initials: MJ
authors.lastname: Santos-Martinez
authors.forename: C
authors.initials: C
authors.lastname: Medina
authors.forename: M W
authors.initials: MW
authors.lastname: Radomski
mesh_terms: D000199:Actins / Q000378:metabolism; D000230:Adenocarcinoma / Q000097:blood* / Q000000981:diagnostic imaging / Q000473:pathology; D001081:Apyrase / Q000494:pharmacology; D001792:Blood Platelets / Q000000981:diagnostic imaging / Q000473:pathology / Q000502:physiology*; D002450:Cell Communication / Q000502:physiology; D045744:Cell Line, Tumor; D015536:Down-Regulation; D004492:Edetic Acid / Q000494:pharmacology; D011464:Epoprostenol / Q000494:pharmacology; D005260:Female; D005354:Fibrosarcoma / Q000097:blood* / Q000000981:diagnostic imaging / Q000473:pathology; D005434:Flow Cytometry; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D018613:Microscopy, Confocal / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D010051:Ovarian Neoplasms / Q000097:blood* / Q000000981:diagnostic imaging / Q000473:pathology; D019007:P-Selectin / Q000097:blood; D010618:Phenanthrolines / Q000494:pharmacology; D015539:Platelet Activation / Q000502:physiology; D010974:Platelet Aggregation / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014465:Ultrasonics / Q000379:methods; D014463:Ultrasonography
chemical_list: D000199:Actins; D019007:P-Selectin; D010618:Phenanthrolines; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D004492:Edetic Acid; D011464:Epoprostenol; D020778:Matrix Metalloproteinase 2; D001081:Apyrase; C025205:1,10-phenanthroline