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.