the oligosaccharide sialylated lewis x (sle(x)) is expressed on the surface of tumor cells and can be recognized by e-selectin and p-selectin, playing on a key role in metastasis of the tumor. however, in the 4t1 breast cancer cell line, e-selectin reactivity is sle(x) dependent while p-selectin reactivity is sle(x)-independent, suggesting p-selectin binding is ca-independent and sulfation-dependent. one of the sulfated ligands is chondroitin sulfate, a type of glycosaminoglycan (gag). its activity in tumor metastasis has been probed by the addition of heparin that functions to blocks tumor metastasis. in addition to gags, mucin is of interest in p-selectin mediated tumor metastasis. selective removal of mucin results in reduced interaction between p-selectin and platelets in vivo and in vitro.