Intercellular Adhesion Molecule-1 (ICAM-1/CD54), a cell surface glycoprotein belonging to the immunoglobulin superfamily. Normally, ICAM-1 is involved in leukocyte adhesion and transmigration during inflammatory responses, and it is expressed at low levels on various cells. In the context of multiple myeloma, ICAM-1 is consistently and highly overexpressed on malignant plasma cells and is also upregulated on bone marrow stromal and endothelial cells. This overexpression contributes to tumor cell adhesion to the bone marrow microenvironment, which promotes survival, growth, and drug resistance.