CK2 kinase activity in MM cells. Graph shows the levels of CK2-specific kinase activity in MM cell lines (▪), CD138⁺ purified plasma cells from 7 MM patients (), in vitro-generated normal plasma cells (nPCs), and purified CD19⁺ B lymphocytes from healthy donors (□). Samples N1 to N3 were from peripheral blood; samples N4 and N5 were from tonsil; samples N6 and N7 were from spleen. Data are mean ± SD.