In a variety of cells ranging from epithelial cells, macrophages, and CD4+ T cells to cells from tumors, such as myeloma, pancreatic cancer, and melanoma, membrane CD138 is cleaved by different proteinases, such as MMP9, MT1-MMP, MT3-MMP, collagenase, and trypsin (11, 13, 19, 27, 28, 29, 30). Here, MT3 is linked to melanoma.