title: Inhibition of platelet GPIb alpha and promotion of melanoma metastasis.
abstract: Platelet glycoprotein Ibalpha (GPIb alpha) is part of the receptor complex GPIb-V-IX, which has a critical role in hemostasis, especially through interactions with the subendothelial von Willebrand factor. As there is accumulating evidence for a contribution of platelet receptors to hematogenous tumor metastasis, GPIb alpha is an interesting molecule to study in this context. We have investigated the effect of GPIb alpha inhibition by monovalent Fab fragments on experimental pulmonary metastasis in a syngeneic mouse model using C57BL/6 mice and B16F10 melanoma cells. The early fate of green fluorescent protein (GFP)-transfected melanoma cells under GPIb alpha blockade was also assessed, as was the effect of GPIb alpha inhibition on pulmonary metastasis in mice lacking P-selectin. Surprisingly and, to our knowledge previously unreported, GPIb alpha inhibition led to a significant increase in pulmonary metastasis, and assessment of the early fate of circulating GFP-labeled B16F10 showed improved survival and pulmonary arrest of tumor cells shortly after GPIb alpha inhibition, indicating that inhibition of a platelet protein can, in some cases, promote metastasis of a malignant tumor. In contrast, GPIb alpha blockade in P-selectin-deficient mice had no enhancing effect on metastasis, suggesting the involvement of GPIb alpha in the initial, P-selectin-dependent steps of metastasis. These findings suggest that GPIb alpha contributes to the control of tumor metastasis, in addition to its role in hemostasis.
authors.affiliation: Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, Julius Maximilians University, Würzburg, Germany.
authors.forename: Luise
authors.initials: L
authors.lastname: Erpenbeck
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nieswandt
authors.forename: Margarete
authors.initials: M
authors.lastname: Schön
authors.forename: Miroslava
authors.initials: M
authors.lastname: Pozgajova
authors.forename: Michael P
authors.initials: MP
authors.lastname: Schön
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006487:Hemostasis; D007150:Immunohistochemistry / Q000379:methods; D008175:Lung Neoplasms / Q000473:pathology; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology*; D008546:Melanoma, Experimental; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors*; D051379:Mice; D008810:Mice, Inbred C57BL; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D019038:Platelet Glycoprotein GPIb-IX Complex; D051381:Rats; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology*
chemical_list: D008562:Membrane Glycoproteins; D019038:Platelet Glycoprotein GPIb-IX Complex; C094990:adhesion receptor; D049452:Green Fluorescent Proteins