Reversal of adriamycin resistance in vitro by TPL. K562/A02 cells were incubated with 3 μg/ml of adriamycin in the presence of, or without, TPL for 24 h. The rates of apoptosis were measured using flow cytometry. The cell inhibition rate was measured by MTT. (A) Apoptosis in K562/A02 cells; (B) apoptosis in K562/A02 treated with TPL; (C) apoptosis rate; (D) inhibition rate. MTT, 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide; TPL, triptolide; ADR, adriamycin; PI, propridium iodide.