TRAIL induces cell death of freshly isolated MM patient cells.

(A) Representative 3-dimensional cell cycle profile analysis, by PI staining, of freshly isolated CD38⁺/CD45RA⁻malignant cells of a patient with plasma cell leukemia. (The longitudinal axis corresponds to intensity of PI staining and the vertical axis to number of events.) A 24-hour incubation with TRAIL induced significant cell death documented by the shift of cells to the sub-G₁ region (indicated by the dark shaded portions of the cell cycle profiles). (B,C) Effect of TRAIL on freshly isolated MM patient BMMCs. Dual-color flow cytometry for CD38-FITC and Apo2.7-PE indicates that late apoptotic (Apo2.7-PE⁺) cells are present only in the population of CD38⁺ BMMCs, which contains MM plasma cells. Quadrants were set based on negative controls stained with MsIgG1-FITC and MsIgG1-PE (X-axis, Apo2.7 relative expression; Y-axis, CD38 relative expression).