Cell viability assay

For the MTT assay, 10⁴−10⁵ cells per well were plated in triplicate in a 96-well clear bottom microassay plate and assayed per manufacturer’s instructions. Cells containing formazan (MTT) were dissolved in 50–75 μL DMSO and formazan concentration was measured by absorbance at 540 nm. For the 10-day cell viability assessment, 5 × 10⁴ cells per well were plated in a 24-well plate and cultured for 10 days. Trypan blue assay was carried out every 2 days to assess the effect of lenalidomide on cells. The number of viable cells were counted using hemocytometer every 2 days. The assays were run in technical triplicate with GST-PTR1 treatment and the data were normalized to mean of GST control. Then, the means of three independent biological replicates were averaged to determine the mean and SD reported. The following concentrations of drugs (Table 1) were used: