For dose-response assays, percentage maximum cell count and percentage of cells with micronuclei were plotted against drug concentration (Figure 2). Results show that micronuclei count increases with the drug treatment until toxic doses are reached and cells begin to detach from the plate.
Percentage maximum cell count relative to untreated controls can be used as a crude index of cell proliferation (PI), which typically decreases with increasing exposure to genotoxins.
Drug concentration at half maximal proliferation (PI50) was determined to be 127 nM for mitomycin C and 176 nM for etoposide (Table 2). These values are within the 95% confidence intervals of values obtained with the standard-chip camera, and correspond well with those reported in the literature (198 and 216 nM respectively) during validation of an automated micronucleus screening assay using GE Healthcare’s IN Cell Analyzer 1000.