Serological detection of Epstein-Barr virus (EBV) antibodies is frequently used in nasopharyngeal carcinoma (NPC) mass screening. However, the large number of seropositive subjects who require close follow-up is still a big burden. The present study aimed to detect the nasopharyngeal EBV load in a high-risk population seropositive for antibodies against EBV, as well as to examine whether assay for nasopharyngeal EBV DNA load might reduce the number of high-risk subjects for follow-up and improve early detection of NPC. A prospective and population-based cohort study was conducted in southern China from 2006 through 2013. Among 22,186 participants, 1045 subjects with serum immunoglobulin A (IgA) antibodies against viral capsid antigen (VCA) titers ≥ 1:5 were defined as high-risk group, and were then followed-up for NPC occurrence. Qualified nasopharyngeal swab specimens were available from 905 participants and used for quantitative PCR assay. Our study revealed that 89% (802/905) subjects showed positive EBV DNA in nasopharyngeal swab. The nasopharyngeal EBV load in females was higher than that in males. The nasopharyngeal EBV load increased with increasing serum VCA/IgA titers. Eight cases of newly diagnosed NPC showed an extremely elevated EBV load, and 87.5% (7 of 8 patients) were early-stage NPCs. The EBV loads of 8 NPCs were significantly higher than those of 897 NPC-free subjects (mean, 2.8×106 copies/swab [range 4.8×104-1.1×108] vs. 5.6×103 [range 0-3.8×106]). Using mean EBV load in NPC-free population plus two standard deviations as cut-off value, a higher diagnostic performance was obtained for EBV load test than serum VCA/IgA test (area under ROC, 0.980 vs 0.895). In conclusion, in a prospective and population-based study we demonstrated that an additional assay of EBV load in the nasopharynx among high-risk individuals may reduce the number of subjects needed to be closely followed up and could serve as part of a NPC screening program in high-risk populations.

Nasopharyngeal carcinoma (NPC) is a highly invasive and metastatic head and neck cancer. However, mechanistic study of the invasion and metastasis of NPC has been hampered by the lack of proper in vivo models. We established an in vivo chick embryo chorioallantoic membrane (CAM) model to study NPC tumor biology. We found 100% micro-tumor formation 3 days after inoculation with NPC cell lines (4/4) or primary tumor biopsy tissue (35/35). The transplanted NPC micro-tumors grew on CAMs with extracellular matrix interaction and induced angiogenesis. In addition, the CAM model could be used to study the growth of transplanted NPC tumors and also several important steps of metastasis, including tumor invasion by detecting the extent of basement membrane penetration, tumor angiogenesis by analyzing the area of neo-vessels, and tumor metastasis by quantifying tumor cells in distant organs. We established and described a feasible, easy-to-manipulate and reliable CAM model for in vivo study of NPC tumor biology. This model closely simulates the clinical features of NPC growth, progression and metastasis and could help elucidate the biological mechanisms of the growth pattern and invasion of NPC cells and in quantitative assessment of angiogenesis and cell intravasation.

BackgroundCytochrome b5 reductase 2 (CYB5R2) is a potential tumor suppressor that inhibits cell proliferation and motility in nasopharyngeal carcinoma (NPC). Inactivation of CYB5R2 is associated with lymph node metastasis in NPC. This study aimed to explore the mechanisms contributing to the anti-neoplastic effects of CYB5R2.MethodsPolymerase chain reaction (PCR) assays were used to analyze the transcription of 84 genes known to be involved in representative cancer pathways in the NPC cell line HONE1. NPC cell lines CNE2 and HONE1 were transiently transfected with CYB5R2, and data was validated by real-time PCR. A chick chorioallantoic membrane (CAM) embryo model was implanted with CYB5R2-expressing CNE2 and HONE1 cells to evaluate the effect of CYB5R2 on angiogenesis. An immunohistochemical assay of the CAM model was used to analyze the protein expression of vascular endothelial growth factor (VEGF).ResultsIn CYB5R2-transfected NPC cells, PCR assays revealed up-regulated mRNA levels of Fas cell surface death receptor (FAS), FBJ murine osteosarcoma viral oncogene homolog (FOS), phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1), integrin beta 3 (ITGB3), metastasis suppressor 1 (MTSS1), interferon beta 1 (IFNB1), and cyclin-dependent kinase inhibitor 2A (CDKN2A) and down-regulated levels of integrin beta 5 (ITGB5), insulin-like growth factor 1 (IGF1), TEK tyrosine kinase (TEK), transforming growth factor beta receptor 1 (TGFBR1), and VEGF. The angiogenesis in the CAM model implanted with CYB5R2-transfected NPC cells was inhibited. Down-regulation of VEGF by CYB5R2 in NPC cells was confirmed by immunohistochemical staining in the CAM model.ConclusionCYB5R2 up-regulates the expression of genes that negatively modulate angiogenesis in NPC cells and down-regulates the expression of VEGF to reduce angiogenesis, thereby suppressing tumor formation.