Cytotoxicity and apoptosis induction in GSTP1-transfected Raji clones.GSTP1-transfected RG20 cells and empty vector–transfected RV7 cells were untreated or treated with As₂O₃ at the indicated concentrations for indicated times. Cytotoxicity (A) was determined by trypan blue staining, and relative levels of apoptotic cells (B) were determined on flow cytometry by Annexin V and PI staining, as described in “Materials and methods.”