VCAM1 and plasma cell myeloma: Furthermore, VCAM-1 as well as other adhesion molecules, such as ICAM-1, are involved in a mechanism called 'cell adhesion-mediated drug resistance' (CAM-DR), which is thought to be one of the major mechanisms by which MM cells escape the cytotoxic effects of therapeutic agents.7, 19 Primarily, multidrug-resistant patients were shown to have significantly higher expression levels of VLA-4 (the receptor of VCAM-1) and ICAM-1 than responders, suggesting that these molecules are implicated in chemotherapeutic agent resistance by myeloma cells.20