PGE2 induces both membrane-associated and soluble MMP-9 expression. (A) CD11c+ DCs were treated with TNF-α plus IFN-α in the presence or absence of PGE2 for 24 hours in serum-free conditions. Cells were stained with goat anti–mouse MMP-9 antibody for 40 minutes, followed by PE-donkey anti–goat IgG for 40 minutes. Expression of membrane-associated MMP-9 was measured by FACS. (B) CD11c+ DCs were treated with PGE2 (10⁻⁶ M) or TNF-α IFN-α plus or minus PGE2 for 24 hours followed by FACS for CD11b and CD44 expression. (C) CD11c+ DCs were stimulated with TNF-α plus IFN-α (in the presence or absence of PGE2 (10⁻⁶ M) for 48 hours. Supernatants were collected, and the amounts of secreted pro–MMP-9 were determined by using the pro–MMP-9 Quantikine assay. Data are representative of 3 independent experiments for panels A and C, and of 2 representative experiments for panel B.