shRNA inhibits and delays development of myeloma tumors. CAG cells infected with control shRNA (control) or syndecan-1 shRNA (Syn^low) were injected subcutaneously into mice. Animals were considered positive for tumor formation when serum kappa light chain levels reached 50 ng/mL. The plot shows the percentage of animals that were free of tumor at weekly intervals for 8 weeks after injection of tumor cells.