CK2α expression in MM cells. (A) Top panel: Western blot for CK2α. Bottom panel: Corresponding Western blot for α-tubulin as a loading control (different sets of experiments are shown). Analyses were performed on the same samples as in Figure 1, corresponding to MM cell lines (lanes 2-5, U266, RPMI, or OPM, as indicated), CD138⁺ purified plasma cells from 5 MM patients (lanes 6-11), normal plasma cells (lane 12, indicated as nPCs), normal CD19⁺ B lymphocytes purified from 7 healthy donors (lanes 13-19). In lane 1, recombinant CK2α was loaded as a positive control; in lanes 5 and 8, TBB (2 μM) was added in vitro to exclude the effects on CK2α levels. (B) Results of 2 representative experiments of immunofluorescence microscopy on freshly isolated bone marrow cells from 2 MM patients stained with an antibody recognizing the specific plasma cell marker CD138 (i,iv; green fluorescence), anti-CK2a (ii,v; red fluorescence), and merged images (iii,vi). Original magnification × 60, oil objective.