Fig 2: Suppression of COX-2 expression by IFN-a via inhibition of the TPL2 and cAMP/CREB. (a) T24 cells were treated with IFN-a (1 × 104 U/mL) for specific time points; or treated using various concentrations of IFN-a for 24 h. The cell lysates were immunoblotted with COX-2 antibody. ß-Tubulin staining is shown as a loading control. (b) T24 cells were treated with IFN-a (1 × 104 U/mL) for specific time points. The TPL2, p-TPL2, IKKa/ß, p- IKKa/ß, I?Ba and p-I?Ba were analyzed by performing western blotting. (c) T24 cells were treated with IFN-a (1 × 104 U/ml), TPL2i (2 µM), and PD98059 (40 µM) for 12 h. The COX-2, TPL2, p-TPL2, ERK, p- ERK, IKKa/ß, p-IKKa/ß, I?Ba and p-I?Ba were analyzed by performing western blotting. ß-Tubulin staining is shown as a loading control. (d) The intracellular cAMP level was detected after T24 cells were treated with IFN-a (1 × 104 U/mL), TPL2i (2 µM), and PD98059 (40 µM) for 4 h. (e) T24 cells were treated with IFN-a (1 × 104 U/mL), TPL2i (2 µM), PD98059 (40 µM), or forskolin (50 µM) for 24 h. The expression levels of COX-2, CREB, and p-CREB were analyzed by western blotting. The ß-tubulin was used as the loading control. (f) T24 cells were treated with IFN-a (1 × 104 U/mL), PD98059 (40 µM), and EGF (25 ng/mL) for 12 h. The COX-2 expression was analyzed by performing western blotting. (g) Cell viability was detected after T24 cells were treated using forskolin (50 µM), TPL2i (2 µM), and PD98059 (40 µM) for 72 h. Data represent the results of three independent experiments. Error bars indicate mean ± SD. *, P < 0.05; **, P < 0.01; #, P < 0.05 (t-test)

Fig 3: Synergistic antitumor effect of IFN-a and roflumilast on MIBC. (a) In MIBC, TPL2 is phosphorylated and activates IKK complexes. Therefore, NF-?B is activated and results in COX-2 overexpression that promotes the MIBC development. Moreover, TPL2 induces COX-2 expression by the enhancement of cAMP/CREB signaling through ERK-mediated inhibition of PDE4D activity. (b) IFN-a-induced TPL2 inhibition leads to down-regulation of COX-2 expression and exerts the anti-tumor effect in MIBC treatment. PDE4D induction by roflumilast synergizes with IFN-a activity to inhibit COX-2 expression through the reduction of cAMP level and potentiates the anti-tumor effect of IFN-a on MIBC