In multiple myeloma (MM), induction of SGK1 expression by the cytokines interleukin (IL)-6, tumor necrosis factor-α (TNF-α), and IL-21 significantly supported the growth of myeloma cells, whereas downregulation of SGK1 with shRNAs resulted in decreased proliferation of myeloma cells and reduced cell numbers (39). This evidence concerns the gene IL21 and plasma cell myeloma.