Flow cytometry was performed on the human in H929, U266, and 5TGM1 mouse multiple myeloma cells as described previously (32 (link)). Apoptosis was analyzed using Annexin V. Anti-human integrin αvβ3 antibody, clone LM609 (Millipore Corporation), anti-mouse integrin α4 and β1 (eBiosciences), and rhodamine-labeled NPs were used for flow cytometry (FACScalibur flow cytometer; Becton Dickinson Immunocytometry Systems). Analysis was performed using FLOJO software (Tree Star).