Abstract 6127: Single-cell spatial transcriptome sequencing characterizes CD70+ immune-resilient nasopharyngeal carcinoma cells as a vital mediator of Treg-induced suppression
Authors: Gong Lanqi , Luo Jie , Yang Yuma , Zhang Yu , Guan Xin-Yuan 
Published: June 2022

Abstract
Background: The microenvironment of nasopharyngeal carcinoma (NPC) has an intense and heterogenous immune infiltration, due to chronic EBV infection and locoregional lymphoid structures. Phase II clinical trials have shown that the response rate of NPC patients to PD-1 inhibitors is only 20%, indicating the current immunotherapies are not optimal due to insufficient understanding of the tumor-immune interaction. In this study, we have applied an integrated transcriptome sequencing analysis to decipher immune dynamics, and have characterized a new target that can inhibit Treg-mediated suppression in NPC, and provided critical translational evidence to the precision immunotherapy.
Methods: We established an integrated NPC single-cell sequencing cohort containing 189,750 T cells from 50 patient samples. Spatial transcriptome sequencing was performed on frozen samples from eight NPC patients. The whole blood was collected from healthy donors and PBMCs were isolated using density gradient centrifugation. T cells were magnetically isolated from PBMCs. The humanized mouse model was established by tail-vein injection of CD3/CD28 activated PBMCs.
Results: Single-cell sequencing revealed the enrichment of suppressive Tregs in the NPC microenvironment. We found that the C666-1 cell line facilitated Treg differentiation and activation. Spatial sequencing identified CD70-CD27 interaction was upregulated between NPC cells and suppressive Tregs, indicating its role in regulating Treg function. CD70 was predominantly expressed on NPC cells and correlated to worse prognosis. CD70-knockout (KO) in C666-1 inhibited Treg differentiation. Decreased Treg activities further enhanced the cytotoxicity in CD8+ effector T cells, leading to higher tumor apoptosis. Cusatuzumab also generated a comparable inhibitory effect in Treg-mediated suppression. In the humanized mouse model, CD70-KO and inhibition shrank the size of subcutaneous tumors by enhancing T cell immunity.
Conclusion: The enrichment and activation Tregs makes the NPC microenvironment highly immunosuppressive, which might jeopardize the clinical efficacy of anti-PD1 therapies in NPC patients. In this study, we revealed that CD70+ NPC cells were highly resilient to immune surveillance since they were capable of modulating Treg differentiation and activation via the CD70-CD27 interaction to counteract CD8+ T cells. Blocking CD70 has been shown to effectively induce tumor apoptosis by alleviating Treg-mediated suppression. The therapeutic efficacy and safety of the anti-CD70 therapy were tested in the humanized mouse model. These findings suggested that the anti-CD70 therapy exhibited a promising efficacy to kill NPC cells by deteriorating the immunosuppressive microenvironment, and it might synergistically enhance the efficacy of anti-PD1 therapies.
Citation Format: Lanqi Gong, Jie Luo, Yuma Yang, Yu Zhang, Xin-Yuan Guan. Single-cell spatial transcriptome sequencing characterizes CD70+ immune-resilient nasopharyngeal carcinoma cells as a vital mediator of Treg-induced suppression [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 6127.