Generation of reactive oxygen species by xanthine derivatives in MDA‐MB‐231 human breast cancer cells

Theophylline reduces cell number in MDA‐MB‐231 cells through mechanisms over and above phosphodiesterase inhibition. In the current study, we used an intracellular fluorescent dye to show that theophylline and, to a much greater extent, 3‐isobutyl‐1‐methylxanthine, evoke the generation of reactive oxygen species and also sensitize the cells to insult by other oxidants. Xanthine derivatives may therefore offer novel strategies for antitumor therapeutics.