SOST and plasma cell myeloma: To examine the effects of CIITA on myeloma cell TP/2DDR–induced cytokine expression in osteocytes, we used shRNAs to knock down CIITA in MLO-Y4 and MLO-A5 cells and found that the knockdown significantly reduced the effect of 2DDR on Sost mRNA levels in osteocytes (Fig. 4a).