PLATELET FACTORS INDUCE CHEMOTACTIC MIGRATION OF MURINE MAMMARY ADENOCARCINOMA CELLS WITH DIFFERENT METASTATIC CAPABILITIES

The chemotactic response of neoplastic cells (NC) induced by soluble p latelet factors was investigated. NC suspensions isolated from murine mammary gland adenocarcinomas having different metastatic capabilities were incubated in Boyden's chambers and challenged with (1) 'Early Pl atelet Factors' (EP), obtained from the soluble fraction of recently c ollagen-activated human platelets, and (2) 'Late Platelet Factors' (LP ), isolated after 24 hours incubation of the platelet aggregates. Chem otaxis was expressed as the distance travelled by NC through nitrocell ulose filters. NC isolated from M3, the tumour line having the stronge r metastatic potential, showed a significant chemotactic response towa rds LP factors, whereas NC from the M2 line exhibiting the lower metas tatic behaviour, showed a chemotactic response towards EP factors. Bot h tumour cell lines lacked motion capability towards the well known ch emoattractant peptide N-f-Met-Leu-Phe-Phe as well as to serum, plasma, collagen type I or culture medium. The different chemotactic response of both tumour lines when they were challenged by concentration gradi ents of factors released by early or late collagen-activated human pla telets, confirm a relationship between platelet activity and metastati c capabilities and suggests that platelet chemoattractants might play a role in the metastatic dissemination of these mammary gland adenocar cinomas.