Induction of apoptosis by celecoxib or DMC. RPMI8226 or drug-resistant 8226/Dox40 cells were cultured in the presence of various concentrations of celecoxib or DMC for 48 hours. Apoptosis was determined using a TUNEL kit as described in “Materials and methods.” Shown is the percentage of TUNEL-positive (ie, apoptotic) cells, as calculated from several hundred cells assessed by visual inspection under the microscope.