L1CAM and cancer: In cancer cells, L1CAM ectodomain is not only expressed on the cell surface, but can also be shed into the extracellular environment as a soluble form of ~200 kDa, through proteolytic cleavage mediated by two A Disintegrin and Metalloprotease (ADAM) enzymes, specifically ADAM10 and ADAM17, or matrix metalloprotease 16 (MMP-16) [12,13,14].