EBV+ tumors exploit tumor cell-intrinsic and -extrinsic mechanisms to produce regulatory T cell-recruiting chemokines CCL17 and CCL22.

Aparna Jorapur,Dirk G Brockstedt,Oezcan Talay,Mengshu Xu,Lisa A Marshall,Scott Jacobson,Pierre Busson,Sachie Marubayashi,Paul D Kassner,Jeffrey J Jackson,Gene Cutler,David Wustrow,Omar Robles,Mikhail Zibinsky,Dennis X Hu,Valentin Baloche,Christian Munz

doi:10.1371/journal.ppat.1010200

Abstract

The Epstein-Barr Virus (EBV) is involved in the etiology of multiple hematologic and epithelial human cancers. EBV+ tumors employ multiple immune escape mechanisms, including the recruitment of immunosuppressive regulatory T cells (Treg). Here, we show some EBV+ tumor cells express high levels of the chemokines CCL17 and CCL22 both in vitro and in vivo and that this expression mirrors the expression levels of expression of the EBV LMP1 gene in vitro. Patient samples from lymphoblastic (Hodgkin lymphoma) and epithelial (nasopharyngeal carcinoma; NPC) EBV+ tumors revealed CCL17 and CCL22 expression of both tumor cell-intrinsic and -extrinsic origin, depending on tumor type. NPCs grown as mouse xenografts likewise showed both mechanisms of chemokine production. Single cell RNA-sequencing revealed in vivo tumor cell-intrinsic CCL17 and CCL22 expression combined with expression from infiltrating classical resident and migratory dendritic cells in a CT26 colon cancer mouse tumor engineered to express LMP1. These data suggest that EBV-driven tumors employ dual mechanisms for CCL17 and CCL22 production. Importantly, both in vitro and in vivo Treg migration was effectively blocked by a novel, small molecule antagonist of CCR4, CCR4-351. Antagonism of the CCR4 receptor may thus be an effective means of activating the immune response against a wide spectrum of EBV+ tumors.

Highlights

The Epstein-Barr Virus (EBV) is one of the most ubiquitous known human viruses, with most individuals infected during childhood or adolescence [1,2]
We show that EBV+ tumors have amongst the highest levels of Treg of all human tumors, as well as having very high levels of the chemokines C motif chemokine ligand 17 (CCL17) and C motif chemokine ligand 22 (CCL22), signaling molecules that promote the migration of Treg
We found that CCL17 and CCL22 production in different EBV+ tumor cell lines mirrored the levels of production of the EBV protein latent membrane protein 1 (LMP1), and that the LMP1 gene on its own was sufficient to trigger chemokine expression and Treg migration into a mouse tumor model

Summary

Introduction

The Epstein-Barr Virus (EBV) is one of the most ubiquitous known human viruses, with most individuals infected during childhood or adolescence [1,2]. Treg have been shown to be recruited to the TME via C-C motif chemokine ligand 17 (CCL17) and C-C motif chemokine ligand 22 (CCL22; described together as CCL17/22) that are expressed directly by some lymphomas or by infiltrating immune cells within the TME [10,18,19,20,21]. LMP1 contributes to the transformation and survival of B cells by multiple pathways, including the activation of NFκB—putatively the mechanism for CCL17/22 expression in these cells [20,22] While expression of these chemokines by immune cells is widely described, the mechanism for CCL17/22 expression in EBV+ tumors of epithelial origin, such as NPC, is less clear

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Conclusion