Apoptotic susceptibility of the tumor cells to arsenic trioxide is associated with the inherent level of cellular reactive oxygen species

Purpose:To explore the association of the inherent cellular level of reactive oxygen species (ROS) with the susceptibility of the tumor cells to apoptosis induced by arsenic trioxide (As 2O 3). Methods:Low concentration(2 μmol/L) of As 2O 3 was administrated to a pair of the leukemic cell lines, NB4 versus U937, and a pair of the esophageal carcinoma cell line, EC/CUHK1 versus EC1867, to confirm the difference in their susceptibility to apoptosis induced by As 2O 3. Dihydrogenrhodamine123 (DHR123), used as a ROS capture, was incubated with the cells in the absence of As 2O 3 administration. The fluorescent intensity of rhodamine123, which was the product of cellular oxidation of DHR123, was detected by flow cytometry, and ROS was thus measured. Results:For apoptosis induction by 2 μmol/L of As 2O 3 ,NB4 was more sensitive than U937,and EC/CUHK1 more sensitive than EC1867. The inherent cellular ROS level was higher in NB4 than in U937, and also higher in EC/CUHK1 than in EC1867. Conclusions:The difference in cellular ROS level is associated with the cellular susceptibility to apoptosis induction by As 2O 3.