CD47 Overexpression Is Associated with Epstein–Barr Virus Infection and Poor Prognosis in Patients with Nasopharyngeal Carcinoma

PURPOSE: Little is known about the clinical significance of CD47 expression and its association with Epstein–Barr virus (EBV) infection in patients with nasopharyngeal carcinoma (NPC). The aim of this study was to clarify the prognostic value and role of CD47 in EBV-associated NPC. MATERIALS AND METHODS: Sixty-six cases of non-metastatic NPC were retrospectively reviewed. Tissues were collected for immunohistochemical staining of CD47 and the EBV-encoded oncoprotein latent membrane protein 1 (LMP1). Western blotting and quantitative real-time PCR were performed to determine the CD47 and LMP1 levels in common human NPC cell lines. Additionally, CD47 and LMP1 expression in a constructed EBV-positive human NPC cell (CNE-2-EBV+) and a stable cell line transfected with LMP1 plasmid (CNE-2-LMP1) was assessed. Next, we used Western blotting to assess the decrease in CD47 expression on CNE-2-LMP1 cells after transfecting them with small interfering RNA (siRNA)-targeting LMP1. RESULTS: In NPC patients, CD47 overexpression was significantly associated with disease recurrence (P=0.010), leading to poorer disease-free survival (DFS; P=0.002) and overall survival (P=0.021). Multivariate Cox proportional hazards models demonstrated that CD47 (HR=5.452, P=0.016) was an independent prognostic factor of DFS. Moreover, CD47 expression was associated with plasma EBV-DNA copy number and LMP1 tissue expression. Among the human NPC cell lines, CD47 and LMP1 expression was notably higher in the EBV-positive C666-1 cell line than in the EBV-negative cell lines. Furthermore, EBV infection upregulated CD47 expression via LMP1-mediated pathways in human NPC cells. CONCLUSION: This study indicated that CD47 is related to EBV infection in NPC patients, and it is a feasible biomarker.