Fig. 3

The response to CPT among eight selected cell lines with various levels of TOP1 enzyme activity. The cell lines indicated were treated with DMSO (as baseline control) or increasing concentrations of CPT (0.1 to 5 μM). Cellular viability was then measured using PrestoBlue reagent. The viability of the cells in absence of any treatment was included as positive control (Pos). Fluorescence signals were normalized to the positive control in each cell line, as described in Materials and Methods. Data plotted are mean (N = 12) ± SD. a Luminal subtype cell lines, b HER2 subtype cell lines, c TNBC subtype cell lines