Pattern of CD8+ tissue resident memory T cells between local recurrence and distant metastasis in nasopharyngeal carcinoma.

Abstract

e15161 Background: CD8+ T lymphocytes are believed to be the major anti-tumor immune subsets. Consequently, most cancer immunotherapeutic approaches seek to amplify cytotoxic T lymphocytes specific to malignant cells. A recently identified subpopulation of memory CD8+ T cells, named tissue-resident memory T (Trm) cells, persists in non-lymphoid tissues, including solid tumors. This T-cell subset is considered an independent memory T-cell lineage with cytotoxic features. However, their function, spatial location and influence on disease-related outcomes (local recurrence [LR], distant metastasis [DM] in nasopharyngeal carcinoma (NPC), a disease entity characterized by substantial immune infiltrate, remain poorly understood. We aim to close this gap through investigation on the abundance and spatial localization of CD8+ Trm in relation to tumor site (primary or recurrence [LR and DM]). Methods: This retrospective cohort analysis based on 20 NPC patient samples: primary (initial diagnosis; [I; n = 19], recurrence ([LR; n = 14] and [DM; n = 10]). We accessed the spatial localization in tumor tissues within tissue-segmented classifications of either cancer islands (pan-cytokeratin–positive [CK+] areas) or stromal areas (CK– areas). Tumor infiltrating lymphocytes (TILs) among patients from I, LR and DM group was quantified through multiplexed 5-colour opal staining using biomarkers against CD8, CD103, IL17, CK plus DAPI (nuclear cell counterstain). Results: While total CD8+ TILs (total tumor) as well as their spatially localized cell densities (tumor islet [TI] vs. tumor stroma [TS]) did not show any significant changes among I, LR and DM patient groups, a higher proportion of CD8+ TILs in the TI co-express the CD103 molecule, an indication of CD8+ Trm (CD103+CD8+) infiltration (mean CD103+CD8+/CD8+ in TI: 32.1% in I group, 44.8% in LR group, 46.0% in DM group; mean CD103+CD8+/CD8+ in TS: 19.0% in I group, 26.2% in LR group 26.2% in DM group). Notably, we observed that such augmentation only reached statistically significant within TI from patient in LR group (p = 0.0451). Furthermore, we found that CD8+ Trm in the LR group expressed higher level of cytokine IL-17, which was ~2.1-fold (p = 0.0788) and 3.6-fold upregulated (p = 0.0285) as compared to I and DM, respectively. Conclusions: Cancer islet–localized CD8+ TILs are composed of CD103+ Trms, which make up nearly 45% the total CD8+ T cell population within LR tumors of NPC patients, highlighting spatial localization of CD103+CD8+ Trms as a key phenotype of CD8+ TIL subset. The CD8+ Trm expressed with increased IL17 suggests that enrichment of this T-cell subset might exerts cytotoxic functions. Our results demonstrate that CD8+ Trm had a greater likelihood as an indicator of LR risk for NPC patients and help identify patient cohorts likely to benefit from immunotherapy.