Mechanisms of Epstein‐Barr virus nuclear antigen 1 favor Tregs accumulation in nasopharyngeal carcinoma

Background Documented reports proved that Epstein‐Barr virus (EBV) infection increased infiltration of Tregs in malignancy. However, the mechanism of EBV recruitment Tregs into nasopharyngeal carcinoma (NPC) tissues has not been detailed discussion. Methods Expression of EBV nuclear antigen 1 (EBNA1) and Foxp3 in NPC tissue samples was detected by immunohistochemistry. EBNA1+ NPC cell lines were used to coculture with PBMC, naïve T cells, Tregs, and monocytes. Percent of Treg was detected by flow cytometry. Results EBNA1 protein was overexpressed in NPC tissues, and was associated with a number of infiltrated Tregs. EBNA1+ NPC cells converted naïve T cells into Tregs by up‐regulated TGF‐β1. Enhanced CCL20 production in EBNA1‐expressed tumor cells increased Tregs migration. Polarized‐M2 macrophages by EBNA1 expression cells converted naïve T cells into Tregs. Conclusions EBNA1 favors accumulation of Tregs in NPC through: (a) upregulated TGF‐β1 converted naïve T cell into Treg; (b) upregulated CCL20 increased Treg migration; and (c) polarized‐M2 macrophage converted naïve T cell into Treg.
It is well known that Tregs accumulated in several EBV‐associated malignancies. Our previous studies also proved Tregs increased in NPC tissues and peripheral blood. However, the mechanism of EBV recruitment Tregs into NPC tissues has not been discussed in detail. EBNA1 protein was highly expressed in NPC tissue specimens, and its expression was associated with number of infiltrated Tregs. EBNA1 expression NPC cells induced naïve T cells into Tregs by upregulated TGF‐β1. Enhanced CCL20 production in EBNA1‐expressed tumor cell increased Tregs migration. Polarized‐M2 macrophages by EBNA1 expression cells converted naïve T cells into Tregs. These findings provided novel insight into the vital role of EBNA1 in recruitment of Tregs in NPC.