Low expression of BEX1 predicts poor prognosis in patients with esophageal squamous cell cancer.

The brain expressed x­linked gene 1 (BEX1) is a member of the BEX family and is aberrantly expressed in many cancers. However, the clinical significance of BEX1 expression level and its role in the pathology of esophageal squamous cell cancer (ESCC) remain unknown. In the present study, we determined BEX1 expression in the tumor and adjacent normal tissues from 118 ESCC patients by immunohistochemistry and determined the proliferation and growth of ESCC cells following ectopic overexpression of BEX1 in cultured cells and in mouse­ESCC xenografts. We observed that BEX1 was downregulated in ESCC tissues compared to adjacent normal tissues, and low BEX1 expression was significantly associated with larger ESCC tumor volume (P<0.001), advanced T stage (P=0.011) and advanced clinical stage (P=0.039). Additionally, survival analysis revealed that low expression of BEX1 significantly predicted poor prognosis in patients with ESCC (P<0.001). Multivariate analysis revealed that low BEX1 expression was an independent prognostic factor of poor survival (P=0.039). In vitro analysis revealed that overexpression of BEX1 inhibited ESCC cell proliferation and colony formation. Furthermore, in vivo tumorigenesis assays revealed that ectopic overexpression of BEX1 suppressed ESCC tumor growth in mice. Further immunoblotting analysis demonstrated that BEX1 upregulation led to reduced expression and phosphorylation of NF­κB p65, indicating inhibition of the NF­κB signaling pathway by BEX1. Our findings indicated that low BEX1 expression may be an independent prognostic marker for poor survival and may serve as a potential target for ESCC therapy.