The tight correlation between Syndecan-1/CD138 expression and aggressiveness of MM cells is corroborated by the enhanced intravasation and bone-infiltration capabilities exhibited by such cells in myeloma-bearing mice in which systemic treatment with an anti-Syndecan-1/CD138 antibody interferes with dissemination of the cells [74]. The gene discussed is SDC1; the disease is plasma cell myeloma.