Platelet antithrombin defect in malignancy: platelet protein alterations
EM Sloand, DM Kenney, FC Chao, J Lawler and JL Tullis
Sixty-eight patients with malignant disease were divided into two groups
based on the results of the platelet antithrombin test (PAT). The normal
group had a PAT clotting time ranging from 21.4 to 29.8 seconds, which was
equivalent to 25% to 65% inactivation of the 2 U of thrombin added to the
test system. The other group showed abnormal PAT clotting time, less than
21.4 seconds or less than 25% thrombin inactivation. The polypeptide
composition of platelets from the two patient groups was analyzed by sodium
dodecyl sulfate (SDS)- electrophoresis on 7.5% polyacrylamide gels. A
polypeptide of 180,000 apparent mol wt was decreased or absent in both
Coomassie blue- and Alcian blue-stained gels of the platelets from patients
whose PAT was abnormal; this polypeptide comigrated with purified platelet
thrombospondin. Tritium labeling of platelet surface glycoproteins by the
periodate-borohydride method followed by two-dimensional electrophoresis
was performed on platelets of seven patients with abnormal PAT. When they
were compared with ten patients with normal PAT, a glycoprotein of 140,000
apparent mol wt with a pl of 4.5 to 5.2 was decreased in platelets of all
seven patients with abnormal PAT. Nitrocellulose replicas of
one-dimensional gels of platelets from 13 of 14 patients with abnormal PAT
showed decreased reaction with an anti- human platelet glycocalicin
antiserum. Platelets of these same patients also showed a decreased or
absent platelet agglutination induced by ristocetin. Patients with normal
PAT had a mean agglutination slope of 1.25 +/- 0.6 (n = 26) as compared
with 0.37 +/- 0.34 (n = 26) for the abnormal PAT group (P less than .001).
Results indicate that platelets from a subpopulation of tumor patients
characterized by decreased platelet antithrombin activity have alterations
in two platelet glycoproteins, identified as GPIb and thrombospondin.
Volume 69,
Issue 2,
pp. 479-485,
02/01/1987
Copyright © 1987 by The American Society of Hematology