Annexin/PI staining, cell cycle analysis, and Apo2.7 staining of MM cells cultured with human recombinant TRAIL.

(A-C) MM cells were cultured with TRAIL (100 and 1000 ng/mL) for 4 hours. Representative dual staining for annexin-FITC/(PI) indicates significant induction of apoptotic cell death (annexin⁺PI⁻ status) of MM-1S MM cells. (D,E) Representative PI staining of MM cells following 24-hour culture with TRAIL (1000 ng/mL) or control cultures. The percentage of cells in the sub-G₁region (indicated in each graph) documents the significant TRAIL-induced cell death of S6B45 and U266 cells. (F) Detection of late apoptosis by staining with the Apo2.7 mAb. The curves corresponding to the MsIgG1-PE control for the TRAIL-treated (standard line) and control (dotted line) cultures of MM-1S cells are superimposable with the (shaded) curve for Apo2.7 staining in the control culture. In contrast, TRAIL-treated MM cells have strong staining for the Apo2.7 (unshaded curve), which is consistent with extensive induction of cell death.