Cell surface glycoprotein that plays a role in cell adhesion and tumor progression (PubMed:2803308, PubMed:2022629, PubMed:1378450, PubMed:8776764, PubMed:11590190, PubMed:10910050, PubMed:14724575, PubMed:16204051). Intercellular adhesion occurs in a calcium- and fibronectin-independent manner (PubMed:2022629, PubMed:16204051). Mediates homophilic and heterophilic cell adhesion with other carcinoembryonic antigen-related cell adhesion molecules, such as CEACAM5 and CEACAM8 (PubMed:2803308, PubMed:2022629, PubMed:8776764, PubMed:11590190, PubMed:16204051). Heterophilic interaction with CEACAM8 occurs in activated neutrophils (PubMed:8776764). Plays a role in neutrophil adhesion to cytokine-activated endothelial cells (PubMed:1378450). Plays a role as an oncogene by promoting tumor progression; positively regulates cell migration, cell adhesion to endothelial cells and cell invasion (PubMed:16204051). Also involved in the metastatic cascade process by inducing gain resistance to anoikis of pancreatic adenocarcinoma and colorectal carcinoma cells (PubMed:10910050, PubMed:14724575). Homodimer; homodimerizes via its Ig-like V-type domain. Heterodimer with CEACAM8; heterodimerizes via its Ig-like V-type domain. Localized to the apical glycocalyx surface. Expressed in neutrophils (PubMed:1378450). Expressed in columnar epithelial and goblet cells of the colon (PubMed:10436421). Expressed in numerous tumor cell lines (at protein level) (PubMed:16204051). Up-regulated in anoikis-resistant pancreatic adenocarcinoma cells (at protein level). The extracellular N-terminus Ig-like V-type domain is necessary for homophilic and heterophilic intercellular adhesion. Glycosylated. Belongs to the immunoglobulin superfamily. CEA family.