The role of CEA-related cell adhesion molecule-1 (CEACAM1) in vascular homeostasis

Carcinoembryonic antigen (CEA)-related cell adhesion molecules belong to the immunoglobulin superfamily, are expressed in a broad spectrum of tissues and cell types and exert context-dependent activating as well as inhibitory effects. Among these molecules, the CEA-related cell adhesion molecule-1 (CEACAM1) is a transmembrane molecule with an extracellular, a transmembrane and a cytoplasmic domain. The latter contains immunoreceptor tyrosine-based inhibitory motifs and functions as a signaling molecule. CEACAM1 can form homo- and heterodimers which is relevant for its signaling activities. CEACAM1 acts as co-receptor that modulates the activity of different receptor types including VEGFR-2, and B and T cell receptors. CEACAM1 is expressed in endothelial cells, in pericytes of developing and newly formed immature blood vessels and in angiogenically activated adult vessels, e.g., tumor blood vessels. However, it is either undetectable or only weakly expressed in quiescent blood vessels. Recent studies indicated that CEACAM1 is involved in the regulation of the endothelial barrier function. In CEACAM1 ^-/- mice, increased vascular permeability and development of small atherosclerotic lesions was observed in the aortae. CEACAM1 is also detectable in activated lymphatic endothelial cells and plays a role in tumor lymphangiogenesis. This review summarizes the vascular effects of CEACAM1 and focuses on its role in vascular morphogenesis and endothelial barrier regulation.