Fig. 3.

Effect of indolequinone 3 treatment on DNA single-strand breaks and DNA cross-links in MIA PaCa-2 and BxPC-3 cells. DNA damage was determined using the comet assay after treating cells with varying concentrations of indolequinone 3 (IQ3) for 1 h. A, DNA single-strand breaks were expressed as percentage of DNA in the comet tail. H₂O₂ treatment (200 μM for 20 min) was included as a positive control. B, comparison of drug-induced DNA single strand breaks in MIA PaCa-2 cells between indolequinone 3 and known redox cycling quinones β-lapachone (β-lap) and streptonigrin (SN). Cells were treated for 1 h. The dose range used for β-lapachone was 1 to 10 μM. C, no DNA cross-links were observed after 1-h indolequinone 3 treatment because there was no decrease in percentage tail DNA in drug-treated cells compared with untreated H₂O₂ control. Results are expressed as the mean ± S.D. of three separate determinations. ^**, significantly different from nontreatment control cells, p < 0.01.