High Expression of Tetraspanin CD63 Predicts Poor Prognosis in Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) has one of the poorest cancer prognosis rates; there is an urgent need to develop new drug therapies and biomarkers. CD63, a tetraspanin protein and well-known exosomal marker, is implicated in cancer progression; however, the significance of CD63 expression in ESCC remains unclear. Herein, we report the significance of CD63 expression by analyzing ESCC patient samples and ESCC cell lines.

ESCC patient samples (n = 86) were evaluated for CD63 expression by immunostaining; univariate and multivariate analysis using Cox proportional hazards were used to evaluate CD63 expression and clinicopathological features as prognostic factors for survival. For in vitro analysis, CD63 knockdown was performed in human ESCC cell lines (TE2 and TE15) using siRNA, and changes in proliferative potential. The gene expression change was also analyzed by microarray and gene set enrichment analysis.

Overall survival was significantly worse in the CD63 high group (p = 0.031, log-rank test). Five-year overall survival univariate analysis identified positive lymph nodes, pStage 3 or higher, and CD63 high expression as poor prognostic factors, while multivariate analysis showed that CD63 high expression was an independent poor prognostic factor (p = 0.009, HR 2.56, 95% CI: 1.269-5.167). CD63 knockdown in ESCC cell lines resulted in a phenotype of decreased proliferative potential. CD63 knockdown increased the expression of genes involved in cell adhesion and suppressed the expression of genes involved in granule secretion. CD63 also shown to affect nuclear import, protein complex localization, and ERBB signaling pathways. In conclusion, CD63 affects gene expression in ESCC, and high tissue expression of CD63 predicts poor prognosis in ESCC patients.