Figure 4.

TOP2α/90 exhibits dominant-negative properties. A: etoposide (1 µM)-induced DNA damage in empty vector and pcDNA/TOP2α/90-transfected K562 cells was determined by neutral comet assays (assessing DNA double-strand breaks) after a 1-h incubation and subtraction of DMSO vehicle controls. The results shown are the mean ± SEM for three experiments run on separate days. *P < 0.025, comparing pcDNA/TOP2α/90-transfected to empty vector-transfected K562 cells; B: etoposide (25 µM)-induced DNA damage in negative control or TOP2α/90-specific Silencer Select Custom Designed TOP2α/90 siRNAs (50 nM) transfected K/VP.5 cells was determined as above. The results shown are the mean ± SEM for five to six experiments run on separate days. *P < 0.025, comparing TOP2α/90 siRNA-transfected to negative control siRNA transfected K/VP.5 cells. For all experimental conditions in each experiment, greater than 100 cells were evaluated by OpenComet software. (A, B) Images are adapted from Figures 4B (left) and Figure 5B (right) respectively, originally published in Molecular Pharmacology; Kanagasabai et al.^[36], 2018. TOP2α: topoisomerase IIα; pcDNA: plasmid cloning DNA; DMSO: dimethyl sulfoxide; siRNA: small interfering RNA