Purification and characterization of the platelet-aggregating sialoglycoprotein gp44 expressed by highly metastatic variant cells of mouse colon adenocarcinoma 26.

A platelet-aggregating sialoglycoprotein with a molecular weight of 44,000 (gp44) was immunochemically purified from highly metastatic mouse adenocarcinoma cells. The rat monoclonal antibody (mAb) 8F11 used in the purification procedure has been generated previously against NL-17 cells derived from the mouse colon 26 cell line, mAb 8F11 inhibits NL-17 cells from inducing platelet aggregation and suppresses their experimental metastasis to the lung. The purified gp44 induced mouse platelet aggregation in a dose-dependent manner without any plasma component. This aggregation was completely inhibited by mAb 8F11. The gp44 was partially characterized by sequential enzymatic hydrolysis of carbohydrates and was found to be O-glycans enriched. When gp44 was sequentially treated with N-glycanase and neuraminidase, it lost platelet aggregation activity. Further treatment with O-glycanase resulted in a loss of the reactivity to mAb 8F11. These results suggest that sialylated carbohydrate chains of gp44 are involved in the induction of platelet aggregation and may play an important role in the colonization of NL-17 cells in the lung.