p-selectin has a functional role in tumour metastasis similar to e-selectin. p-selectin is expressed on the surface of both stimulated endothelial cells and activated platelets, and helps cancer cells invade into the bloodstream for metastasis and provides local multiple growth factors, respectively. moreover, platelets facilitate tumor metastasis by forming complexes with tumour cells and leukocytes in the vasculature, thus preventing recognition by macrophages. this is thought to contribute to the seeding of tumour microemboli in distant organs. in vivo mice experiments have shown that a reduction in circulating platelets could reduce cancer metastasis.