In thisstudy, fibronectin bound to exosomes isolated from myeloma cell cultures was found toregulate exosome–cell interaction, degradation of heparin sulfate on the surface of theexosomes or their recipient cells was found to attenuate this interaction, and thisinteraction could be blocked by heparin sulfate mimetics or antibody blockade of theheparin-II domain of fibronectin. This evidence concerns the gene FN1 and plasma cell myeloma.