15d-PGJ₂down-regulates the expression of cellular inhibitor-of-apoptosis proteins (cIAPs) and cFLIP. (A) HS-Sultan cells were treated with 10 μM 15d-PGJ₂,10 μM dexamethasone (DexaM), or control diluent for 8 hours. Whole-cell lysates were assayed for NF-κB DNA-binding activity by EMSA (top panel) or immunoblotted with the indicated antibodies (lower panels). Inhibition of NF-κB by 15d-PGJ₂ is associated with a decrease in the expression of cIAP-1, cIAP-2, cFLIP, and XIAP. (B) Time-course modulation of IAP protein expression in HS-Sultan cells treated with 15d-PGJ₂ (10 μM) or control diluent. At the indicated times, the levels of cIAP-1, cIAP-2, XIAP, cFLIP, and Bcl-X_L were determined by Western blot analysis. cIAP-1 and cIAP-2 bands are indicated by arrows.