Profiling antigen specificity concurrently with protein and mRNA quantification using high throughput single-cell multiomics reveal surprising similarities between bystander and tumor specific CD8+ tumor-infiltrating lymphocytes (TILs) in renal cell carcinoma (RCC).

Abstract

e15014 Background: Recently, using human colorectal and lung cancer, we showed that CD8+ T cells infiltrating tumor tissue (TILs) are not only specific for tumor antigens, but are also composed of CD8+ TILs specific for cancer unrelated epitopes – called bystander – such as HCMV, EBV or flu epitopes. We also showed that the surface marker CD39 can be useful for discriminating bystander (CD39−) from tumor-specific (CD39+) CD8+ TILs (Simoni et al, Nature, 2018). Methods: Here, our aim was to test these findings in human Renal cell Carcinoma (RCC) and to better understand the biology of these bystander CD8+ TILs. Results: Surprisingly, our primary CYTOF analyses showed heterogeneity within bystander CD8 TILs that possess various phenotypes including effector (CD45RO+), memory (CD45RO+ CCR7+), Trm (CD69+ CD103+/–), and senescent (CD57+ KLRG1+) cell features. Using targeted mRNA single-cell sequencing combined with BD AbSeq assay, we analyzed sorted CD8+ TILs from RCC patients and identified bystander CD8+ TILs using oligo-tagged tetramers. Gene signature analysis of these different subsets revealed transcriptomic similarities with the tumor-specific CD8+ TILs. Conclusions: Our data provide a comprehensive perspective of cancer unrelated CD8+ TILs in RCC and suggest functional roles for these cells in tumor immune responses, which could lead to new diagnostic and therapeutic strategies.