EBAG9 is a tumor‐promoting and prognostic factor for bladder cancer.
Upregulation of EBAG9 expression has been observed in severalmalignant tumors such as advanced breast and prostate cancers,indicating that EBAG9 may contribute to tumor proliferation. Inthe present study, we assess the role of EBAG9 in bladder cancer.We generated human bladder cancer EJ cells stably expressingFLAG-tagged EBAG9 (EJ-EBAG9) or empty vector (EJ-vector),and investigated whether EBAG9 overexpression modulates cellgrowth and migration in vitro as well as the in vivo tumor formationof EJ transfectants in xenograft models of BALB/c nude mice.EBAG9 overexpression promoted EJ cell migration, while theeffect of EBAG9 to cultured cell growth was rather minimal.Tumorigenic experiments in nude mice showed that the size of EJEBAG9-derived tumors was significantly larger than EJ-vectorderivedtumors. Loss-of-function study for EBAG9 using smallinterfering RNA (siRNA) in xenografts with parental EJ cellsshowed that the intra-tumoral injection of EBAG9 siRNA markedlyreduced the EJ tumor formation compared with controlsiRNA. Furthermore, immunohistochemical study for EBAG9expression was performed in 60 pathological bladder cancer specimens.Intense and diffuse cytoplasmic immunostaining wasobserved in 45% of the bladder cancer cases. Positive EBAG9immunoreactivity was closely correlated with poor prognosis ofthe patients (p 5 0.0001) and it was an independent prognosticpredictor for disease-specific survival in multivariate analysis(p 5 0.003). Our results indicate that EBAG9 would be a crucialregulator of tumor progression and a potential prognostic markerfor bladder cancer.