ING4 expression by human myeloma cell lines (HMCLs). ING4 mRNA expression was evaluated by RT-PCR in several HMCLs (U266, XG-1, RPMI-8226, XG-6, OPM-2, JJN3). GAPDH was used as internal control (A). ING4 mRNA levels were quantified by real-time PCR in HMCLs. Data are expressed (graphs) as −ΔCt ING4: −(mean C_{t ING4} − mean C_{t ABL}) plus or minus SD of triplicate measures. Purified tonsil CD138⁺ plasma cells were used as healthy control (B).