Epstein-Barr Virus-Encoded Circular RNA CircBART2.2 Promotes Immune Escape of Nasopharyngeal Carcinoma by Regulating PD-L1.

Abstract

Epstein-Barr virus (EBV) infection is an established cause of nasopharyngeal carcinoma (NPC) and is involved in a variety of malignant phenotypes, including tumor immune escape. EBV can encode a variety of circular RNAs (circRNA), however, little is known regarding the biological functions of these circRNAs in NPC. In this study, EBV-encoded <i>circBART2.2</i> was found to be highly expressed in NPC where it upregulated PD-L1 expression and inhibited T-cell function <i>in vitro</i> and <i>in vivo</i>. <i>circBART2.2</i> promoted transcription of PD-L1 by binding the helicase domain of RIG-I and activating transcription factors IRF3 and NF-κB, resulting in tumor immune escape. These results elucidate the biological function of <i>circBART2.2</i>, explain a novel mechanism of immune escape caused by EBV infection, and provide a new immunotherapy target for treating NPC. SIGNIFICANCE: This work demonstrates that <i>circBART2.2</i> binding to RIG-I is essential for the regulation of PD-L1 and subsequent immune escape in nasopharyngeal carcinoma.