The influence of platelet aggregation inhibitors on metastasis formation in mice (3LL).

Platelets were suggested to play a specific role in the haematogenous spread of experimental tumours. To test this hypothesis mice were treated with various inhibitors or platelet function (acetyl-salicylic acid, RA 233, bencyclan-, cyproheptadine). The effect of treatment on the development of lung colonies after i.v. tumour cell injection as well as on the formation of spontaneous metastases from the solid Lewis-lung carcinoma was evaluated. A significant increase of lung colonies after pretreatment with the platelet aggregation inhibitors was found. The effect of long term treatment on spontaneous metastasis formation gave equivocal results. The present investigations do not support the importance of the integrity of platelet function as a prerequisite for metastasis formation.