Celecoxib inhibits Ewing sarcoma cell migration via actin modulation

Ewing sarcoma (ES) is an aggressive childhood solid tumor in which 30% of cases are metastatic at presentation, and subsequently carry a poor prognosis. We have previously shown that treatment with celecoxib significantly reduces invasion and metastasis of ES cells in a cyclooxygenase-2-independent fashion. Celecoxib is known to downregulate β-catenin independently of cyclooxygenase-2. Additionally, the actin cytoskeleton is known to play an important role in tumor micrometastasis. We hypothesized that celecoxib's antimetastatic effect in ES acts via modulation of one of these two targets.

ES cells were treated with celecoxib, and the levels of β-catenin and total actin were examined by Western blot and quantitative polymerase chain reaction. Cells were transfected with small interfering RNA targeting β-catenin, and invasion assays were performed. Immunofluorescence staining for β-catenin and F-actin was performed on treated and untreated cells. Additionally, cells were subjected to a wound healing assay to assess migration.

Celecoxib had no effect on the messenger RNA or protein levels of β-catenin but did significantly decrease the amount of total actin within ES cells. Reduction of β-catenin by small interfering RNA had no effect on invasion, and celecoxib treatment of the β-catenin depleted cells continued to inhibit invasion. Immunofluorescence staining demonstrated no change in β-catenin with treatment but did show a significant reduction in the amount of F-actin, as well as morphologic changes of the cells. Wound healing assays demonstrated that celecoxib significantly inhibited migration.

Celecoxib does not exert its antimetastatic effects in ES through alteration of β-catenin but does significantly modulate the actin cytoskeleton.