title: Platelet granule secretion continuously prevents intratumor hemorrhage.
abstract: Cancer is associated with a prothrombogenic state capable of platelet activation. Platelets, on the other hand, can support angiogenesis, a process involved in the progression of tumor growth and metastasis. However, it is unclear whether platelet/tumor interactions substantially contribute to tumor physiology. We investigated whether platelets stabilize tumor vessels and studied the underlying mechanisms. We induced severe acute thrombocytopenia in mice bearing s.c. Lewis lung carcinoma or B16F10 melanoma. Intravital microscopy revealed that platelet depletion led to a rapid destabilization of tumor vessels with intratumor hemorrhage starting as soon as 30 min after induction of thrombocytopenia. Using an inhibitor of glycoprotein Ibalpha (GPIbalpha) and genetically engineered mice with platelet adhesion defects, we investigated the role of platelet adhesion receptors in stabilizing tumor vessels. We found that a single defect in either GPIbalpha, von Willebrand factor, P-selectin, or platelet integrin activation did not lead to intratumor hemorrhage. We then compared the ability of transfused resting and degranulated platelets to prevent intratumor hemorrhage. Whereas resting platelets prevented thrombocytopenia-induced tumor bleeding, circulating degranulated platelets did not. This suggests that the prevention of intratumor hemorrhage by platelets relies on the secretion of the content of platelet granules. Supporting this hypothesis, we further found that thrombocytopenia dramatically impairs the balance between propermeability and antipermeability factors in tumor-bearing animals, in particular depleting blood of angiopoietin-1 and serotonin. Our results show a crucial contribution of platelets to tumor homeostasis through continuous prevention of severe intratumor hemorrhage and consequent cell death. The study also suggests platelet function as a reasonable target for specific destabilization of tumor vessels.
authors.affiliation: Immune Disease Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Benoit
authors.initials: B
authors.lastname: Ho-Tin-Noé
authors.forename: Tobias
authors.initials: T
authors.lastname: Goerge
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Cifuni
authors.forename: Daniel
authors.initials: D
authors.lastname: Duerschmied
authors.forename: Denisa D
authors.initials: DD
authors.lastname: Wagner
mesh_terms: D042683:Angiopoietin-1 / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D018827:Carcinoma, Lewis Lung / Q000473:pathology / Q000517:prevention & control*; D049109:Cell Proliferation; D005260:Female; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006470:Hemorrhage / Q000517:prevention & control*; D007124:Immunoenzyme Techniques; D008175:Lung Neoplasms / Q000556:secondary; D008546:Melanoma, Experimental / Q000473:pathology / Q000517:prevention & control*; D008666:Metalloendopeptidases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009336:Necrosis; D019007:P-Selectin / Q000502:physiology; D015539:Platelet Activation; D010973:Platelet Adhesiveness; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000502:physiology; D012701:Serotonin / Q000378:metabolism; D013921:Thrombocytopenia / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014841:von Willebrand Factor / Q000502:physiology
chemical_list: D042683:Angiopoietin-1; C467628:Angpt1 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D006454:Hemoglobins; D019007:P-Selectin; D019038:Platelet Glycoprotein GPIb-IX Complex; C485927:Rasgrp2 protein, mouse; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D014841:von Willebrand Factor; D012701:Serotonin; D008666:Metalloendopeptidases; C070738:O-sialoglycoprotein endopeptidase