Inhibition of pathologic immunoglobulin-free light chain production by small interfering RNA molecules

Morbidity and mortality occurring in patients with multiple myeloma, AL amyloidosis, and light chain deposition disease can result from the pathologic deposition of monoclonal immunoglobulin light chains (LCs) in kidneys and other organs. To reduce synthesis of such components, therapy for these disorders typically has involved antiplasma cell agents; however, this approach is not always effective and can have adverse consequences. We have investigated another means to achieve this objective; namely, RNA interference.SP2/O mouse myeloma cells were stably transfected with a construct encoding a λ6 LC (Wil) under control of the cytomegalovirus promoter, while λ2-producing myeloma cell line RPMI 8226 was purchased from the American Type Culture Collection (Manassas, VA, USA). Both were treated with small interfering RNA directed specifically to the V, J, or C portions of the molecules and then analyzed by enzyme-linked immunosorbent assay, flow cytometry, and real-time polymerase chain reaction.Transfected cells were found to constitutively express detectable quantities of messenger RNA and protein Wil and, after exposure to small interfering RNAs, an ∼ 40% reduction in messenger RNA and LC production was evidenced at 48 hours. An even greater effect was seen with the 8226 cells.Our results have shown that RNA interference can markedly reduce LC synthesis and provide the basis for testing the therapeutic potential of this strategy using in vivo experimental models of multiple myeloma.