IMiD1 enhances TRAIL/Apo2L–mediated apoptosis and down-regulates the expression of the antiapoptotic proteins cIAP-2 and FLIP.

(A) Combined proapoptotic effect of IMiD1 with TRAIL/Apo2L in MM.1S cells. Cells were pretreated with or without 1 μM IMiD1 for 4 hours, and a low concentration of TRAIL/Apo2L (50 ng/mL) was then added for an additional 24 hours. Data shown (mean ± SD) are representative of 3 experiments. IMiD1 potentiated the apoptotic effect of TRAIL/Apo2L. (B) Immunoblotting analysis for the antiapoptotic molecules cIAP-2, FLIP, Bcl-2, ICAM-1, and tubulin in MM.1S cells. Treatment with IMiD1 (1 μM for 72 hours) decreased the protein levels of caspase-8 inhibitors cIAP-2, FLIP, and ICAM-1, but not Bcl-2.