Platelets in tumor metastasis: generation of adenosine diphosphate by tumor
cells is specific but unrelated to metastatic potential
G Grignani and GA Jamieson
American Red Cross Laboratories, Rockville, MD.
Human 253J urinary carcinoma cells and the F1 (low-metastatic) and F10
(high-metastatic) variants of the B16 murine melanoma cell line have been
shown to activate heparinized human platelets by an adenosine diphosphate
(ADP)-dependent mechanism based on inhibition by creatine
phosphate/creatine phosphokinase and the identification of aggregating
concentrations (1 to 2 mumol/L) of ADP in cell-free culture supernatants by
high-performance liquid chromatography. Aggregation did not occur in
citrated samples, and hirudin was without effect. Studies were carried out
to determine whether extracellular ADP arose from nonspecific cell damage
during cell isolation and manipulation or was a specific process under
control of the tumor cells themselves. Tumor cell damage during harvesting
was shown not to be a factor because the amounts of ADP produced by the
three cell lines (a) were inversely related to the appearance of lactic
dehydrogenase in the culture supernatants and (b) were similar when
measured in confluent monolayers, either in tumor cells after detachment
and resuspension or after crossover studies involving culture in,
alternatively, Hanks' balanced salt solution and minimal essential medium.
Metabolic control of ADP production was indicated by the fact that (a) it
was not dependent on cell number, which suggests feedback inhibition; (b)
it was reduced 60% when tumor cells were treated with p-
chloromercuribenzene sulfonate; and (c) it was completely abolished in
those treated with iodoacetic acid, which might be expected to increase
nonspecific leakage. These studies indicate that ADP production by these
three lines does not arise due to leakage induced by nonspecific membrane
damage during cell harvesting and manipulation but is a discrete process
under metabolic control of the tumor cells. Moreover, in B16 murine
melanoma cells the ability to produce ADP and to support platelet
aggregation appears to be unrelated to metastatic potential insofar as
identical results were obtained with the F1 and F10 variants.
Volume 71,
Issue 4,
pp. 844-849,
04/01/1988
Copyright © 1988 by The American Society of Hematology
