Abstract 3192: EBV-products containing exosomes remodel NPC tumor microenvironment by activating fibroblasts

Abstract

Abstract Epstein-Barr virus (EBV) infection is intimately associated with type III nasopharyngeal carcinoma (NPC). Most NPCs respond well to chemoradiation. Nevertheless, approximately 20% of patients experience recurrence and distant metastasis. Tumor desmoplastic responses and high densities of cancer-associated fibroblasts (CAFs) within tumors have been correlated with poorer prognosis. In this study, we demonstrate that EBV activates fibroblasts via exosomes to remodel a pro-tumoral microenvironment. Exosomes derived from NPC cells contained a high level of fibroblast activation protein alpha (FAPα) and EBV-encoded latent membrane protein 1 (LMP1). Treating primary fibroblasts with these exosomes induced functional changes resembling CAFs. Transcriptomic analysis on exosome-treated fibroblasts revealed genes involved in fibrosis-associated pathways were enriched. Noticeably, treating with EBV products-containing exosomes in fibroblasts enhanced the production of several immune-suppressive cytokines, including IL6, IL8, and MCP-1. Moreover, stimulation with these exosomes enhanced activation of YAP1 signaling, a key pathway linking to fibrosis. The in vivo mouse xenografted NPC studies showed that EBV products-containing exosomes markedly enhanced the severity of tissue fibrosis and tumor growth. IHC analysis on mouse NPC xenografts and human NPC biopsies showed a positive correlation between levels of nuclear YAP1 and FAPα, which were further correlated with an enhanced fibrotic response within tumors. Pharmaceutical intervention with YAP1 inhibitors blocked the exosome-mediated effects on fibroblasts. Collectively, our data suggest that EBV products-containing exosome is a causal factor in CAF formation, which constitutes a pro-tumoral microenvironment to benefit the survival of both tumor and virus itself. Citation Format: Po-Ju Lee, Yun-Hua Sui, Chen-Han Huang, Tzu-Tung Liu, Ngan-Ming Tsang, Shu-Chen Liu. EBV-products containing exosomes remodel NPC tumor microenvironment by activating fibroblasts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3192.