Melanoma cell adhesion molecule (MCAM MUC18 CD146) is an immunoglobulin superfamily member identified as a cell surface adhesion protein and a marker for melanoma progression and metastasis MCAM is expressed in vascular endothelial cells activated T lymphocytes smooth muscle and bone marrow stromal cells Its expression increases in endothelial cells from angiogenesis-related disorders such as inflammatory bowel disease Crohn s disease rheumatoid arthritis tumors and chronic renal failure MCAM-expressing human mesenchymal stromal cells (hMSC) help maintain the self-renewal of hematopoietic stem and progenitor cells (HSPC) through direct contact possibly involving Notch signaling Research suggests MCAM also plays a role in multiple sclerosis where endothelial MCAM in the blood-brain barrier facilitates lymphocyte transmigration contributing to inflammatory lesions in the central nervous system