Effect of aminotriazole on clonogenic survival of PC3 cells exposed to doxorubicin. PC3 cells, which had been trypsinized, counted, and allowed to reattach as single cells, were treated with aminotriazole for 2 h, then doxorubicin 100 nM was added. After an additional 1 h, the drug-containing media were removed, cells rinsed, and new media were added. Cultures were incubated for 7–10 days before fixation, staining, and counting. Survival was determined from viable colonies and expressed as percent relative to no-treatment controls. The value for control cells not exposed to doxorubicin or aminotriazole was 100%. Values are the mean percents (±SEM) from three independent experiments.