The metastatic capacity of cancer cells has been strongly associated with increased activity of the plasminogen activation cascade. This results in the conversion of cell-bound plasminogen (pig) by specific pig activators to the active, broad spectrum protease, plasmin . However, while the inappropriate expression of pig activator and their receptors (viz., uPA and uPAR respectively) are well recognised to contribute to breast cancer malignancy, whether cellular pig receptors are also increased and the importance of these molecules in intracellular and extracellular events related to metastasis remain unclear. To date several candidate pig binding proteins have been identified and we have recently shown that the glycolytic enzyme, α-enolase, is an authentic pig binding protein . Tumourogenic and metastatic breast cancer cell lines are EGF-R(+), p185HER2/neu (+), estrogen receptor positive, ER(-) and uPA/uPAR(+). We will present data to show that these cell lines also have a greater pig binding capacity (by flow cytometry, histochemistry and ligand blotting) and that a -enolase may contribute to this finding. Of note is the fact that o> enolase is a cytoplasmic protein without secretion signals nor hydrophobia domains. However, that a-enolase is a known substrate for EOF-R and other kinases and possesses fatty acylation sites. We are currently investigating the intracellular signalling processes that target a-enolase to the cell surface where it may act as a pig receptor. 1 Andronicos, N.M., Ranson, M., Bognacki, J., and M.S. Baker. (1997) Biochim. Biophys. Acta. 1337, 27-39. 1 Ranson, M., Andronicos, N.M., and M.S. Baker. (1997) Br. J. Cancer, submitted.