Cell surface glycoprotein that plays a role in cell adhesion and tumor progression. Intercellular adhesion occurs in a calcium- and fibronectin-independent manner. Mediates homophilic and heterophilic cell adhesion with other carcinoembryonic antigen-related cell adhesion molecules, such as CEACAM5 and CEACAM8. Heterophilic interaction with CEACAM8 occurs in activated neutrophils. Plays a role in neutrophil adhesion to cytokine-activated endothelial cells. Plays a role as an oncogene by promoting tumor progression; positively regulates cell migration, cell adhesion to endothelial cells and cell invasion. Also involved in the metastatic cascade process by inducing gain resistance to anoikis of pancreatic adenocarcinoma and colorectal carcinoma cells.