Abstract
MLN4924 is a specific small-molecule inhibitor of NEDD8-activating enzyme (NAE) that blocks the neddylation modification cascade. Several I/II/III clinical trials suggested that MLN4924 exerts an antitumor effect against various malignancies. However, recent studies have also found that MLN4924 activates the PI3K/AKT and MAPK/ERK signal pathways, important regulators of tumorigenesis, and drug resistance in human urothelial carcinoma (UC). This study examined the synergistic effect of celecoxib, a cyclooxygenase-2 (COX-2) selective inhibitor, on MLN4924-induced cytotoxicity and epithelial-mesenchymal transition (EMT) inhibition via AKT and ERK pathways in human UC. We performed both in vitro and in vivo experiments. Briefly, a combination of MLN4924 and celecoxib reduced the protein expression of p-AKT(S473) and p-ERK in UC cell lines. Moreover, celecoxib shifted the half-maximal inhibitory concentration (IC50) curve of MLN4924 to the left, and the combinational effect of MLN4924 and celecoxib showed significant synergism in T24 and 5637 cells. Also, celecoxib enhanced the MLN4924 antitumor effects of inhibiting UC cell growth, colony formation, migration, invasion, and inducing apoptosis. In addition, celecoxib potentiated the MLN4924-induced EMT, decreased the expression of N-cadherin and vimentin, and activated the expression of E-cadherin. Celecoxib also increased the expression of pro-apoptosis proteins PARP and BAX and reduced the expression of antiapoptosis protein Bcl2. In vivo study indicated that the combination of MLN4924 and celecoxib synergistically suppressed the tumor growth in a UC xenograft nude-mice model, which was further supported by immunohistochemistry of tumor tissues. To sum up, our study revealed that celecoxib synergistically enhanced MLN4924-induced cytotoxicity and EMT inhibition in UC. It also inhibited the activation of AKT and ERK pathways, which were activated by MLN4924. These discoveries provide a new drug combination strategy for UC treatment.