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.