Introduction

Immunotherapy has emerged as a novel therapeutic option for head and neck squamous cell carcinoma (HNSCC), yet only a small fraction of patients produces an effective immune response [1]. The aim of our study was to characterize HNSCC specimens with respect to tumor–infiltrating leukocytes (TILs). We aim at a profound understanding of the immunological processes in the tumor microenvironment (TME), which influence the treatment outcome.

Materials and methods

Treatment – naive HNSCC specimens were subjected to single cell RNA sequencing. Clusters were classified according to common lineage markers and distinct gene expression profiles. TILs were investigated for their differentiation stage. TIL exhaustion was characterized by analyzing the expression of immune checkpoints.

Results

Our preliminary data revealed high proportions of regulatory and memory T cells and the absence of cytotoxic effector T cells. Clusters of exhausted T cells were present in varying proportions. Within the B cell population, the TME was mainly dominated by plasma cells. Macrophages and natural killer cells of various subtypes were identified.

Discussion

The composition of the TILs differed between samples, but the high numbers of regulatory and exhausted T cells indicated an overall immunosuppressive TME. More tumor samples will be subjected to a sophisticated single cell RNA–sequencing approach including V(D)J and phenotype sequencing.

[1] Mei, Z., Huang, J., Qiao, B. & Lam, A. K. (2020). Immune checkpoint pathways in immunotherapy for head and neck squamous cell carcinoma. International Journal Of Oral Science, 12(1). https://doi.org/10.1038/s41368-020-0084-8

This project was funded by the Ministry of Science, Research and Arts Baden–Württemberg, grant no: BW6–07.

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