Fig. 5.

Role of glutathione/oxidative stress in mediating the anticancer activity of arsenic trioxide in 253JB-V cells. [A] Effects of arsenic trioxide and DEM on GSH and ROS. 253JB-V cells were treated with aqueous solvent, arsenic trioxide alone, or in combination with DEM. Cellular GSH levels and ROS were determined as described in the Materials and Methods. Results are expressed at means ± SE and significant (p < 0.05) effects by arsenic trioxide (*) and enhancement by DEM (**) are indicated. GSH values in control (100%), DEM, arsenic trioxide alone or in combination with DEM were 100±0.7, 79.8±0.5, 85.0±0.3 and 44.4±0.4, respectively. ROS values in control (100%), arsenic trioxide alone (5 or 10 μM), DEM alone, and DEM + arsenic trioxide (5 or 10 μM) were 100±2, 85±0.7, 75±1.2, 85±1.7, 163±30 and 368±15, respectively. [B] DEM enhances the antiproliferative activity of arsenic trioxide. 253JB-V cells were treated with solvent control, 2.5, 5 or 10 μM arsenic trioxide alone, or in combination with DEM. After 24 hr, cells were counted as described in the Materials and Methods. Results are means ± SE for 3 determinations for each treatment group and significant (p < 0.05) inhibition by arsenic trioxide (*) and enhancement by DEM (**) are indicated. [C] Sp expression levels. 253JB-V cells were treated with arsenic trioxide alone or in the presence of DEM for 24 hr and whole cell lysates were examined by western blot analysis as described in the Materials and Methods. [D] TUNEL assay. 253JB-V cells were treated with solvent (control), 5 μM arsenic trioxide alone, or in combination with DEM and the TUNEL assay was determined and quantitated as described in the Materials and Methods. The percent of apoptotic cells in control (100%), arsenic trioxide alone, DEM alone, and arsenic trioxide + DEM were 100±25, 193±18, 125±12 and 566±105, respectively. Results are expressed as means ± SE for 2 replicate determinations for each treatment group and significant (p < 0.05) induction of TUNEL staining (*) is indicated.