L. Oleksowicz et al., CHARACTERIZATION OF TUMOR-INDUCED PLATELET-AGGREGATION - THE ROLE OF IMMUNORELATED GPIB AND GPIIB IIIA EXPRESSION BY MCF7 BREAST-CANCER CELLS/, Thrombosis research, 79(3), 1995, pp. 261-274
Tumor cell induced platelet aggregation is thought to be an early step
in the metastatic process. Here we show that platelet aggregation ind
uced by MCF-7 cells is mediated, in part, through an ADP-dependent mec
hanism based on inhibition of aggregation by pretreatment of the tumor
cells with apyrase and the identification of ADP in tumor cell-free s
upernatants by HPLC. By applying immunocytochemical and flow cytometri
c techniques, we demonstrate that platelet immunorelated glycoproteins
, GPIb, GPIIb/IIIa, GPIb/IX, and the integrin a, subunit are expressed
on the surface of MCF-7 cells. The expression of an immunorelated GPI
b was further confirmed by immunoblot and autoradiography of I-125-lab
elled MCF-7 cells. MCF-7 cell immunoblot preparations demonstrated one
major protein reactive to an anti-GPIb alpha MoAb under nonreduced co
nditions with a molecular weight of 200 kD and two major proteins reac
tive with the anti-GPIb alpha MoAb under reduced conditions with molec
ular weights of 92 kD and 38 kD. Platelet aggregation is inhibited by
preincubating the MCF-7 cells with antibodies to GPIb and GPIIb/IIIa.
These findings document expression of adhesive glycoproteins by MCF-7
cancer cells and suggest that these receptors, together with ADP, play
a role in tumor induced platelet aggregation.