Determination of cell viability. (A) GHOST-R5X4 cells were transfected with 3.2 μg/ml, 6.4 μg/ml, 12.8 μg/ml, 25.6 μg/ml or 51.2 μg/ml DBR1 siRNA pHyper-D123 (black bars) or the same concentrations of pHyper alone (white bars) as a control. (B) GHOST-R5X4 cells were transfected with 1 μg/ml, 4 μg/ml, 6 μg/ml CDM9-DBR1 (black bars) or the same concentrations of CDM9 alone (white bars) as a control. After forty-eight hours cellular viability was assayed with a commercial MTS assay kit (Promega). Results shown are from triplicate samples in a representative experiment. Error bars indicate standard deviations.