Background Head and neck squamous cell carcinomas (HNSCCs) arise in the mucosal linings of the upper aerodigestive tract. Risk factors are smoking, excessive alcohol consumption and infection with human papillomavirus (HPV). Tumors are classified according to stage, HPV status, and to anatomical site: oral cavity, hypopharynx, larynx and oropharynx. Immune checkpoint inhibitors belong to the treatment arsenal for HNSCC but are effective in only a minority of patients. Treatment response and prognosis are influenced by the tumor immune microenvironment (TiME). Generally, HPV-related HNSCCs are associated with increased immune infiltration, but for different HNSCC anatomical sites such data are lacking.
Materials and Methods Using flow cytometry, we investigated the TiME of 58 fresh HNSCC samples. We further examined the spatial distribution of CD8+ subsets using multiplex immunohistochemistry (mIHC) on 20 samples. Additionally, single cell RNA-sequencing (scRNA-seq) was performed on five samples to obtain a comprehensive understanding of individual cells in the TiME of HNSCC.
Results Increased T cell frequencies were observed with flow cytometry in oral cavity squamous cell carcinoma (OCSCC) in comparison to HPV-unrelated HNSCC at other anatomical sites. Using mIHC, no significant differences were found in tissue-resident or proliferating CD8+ densities between sites. However, a trend towards increased proliferating CD8+ densities was observed in OCSCC. Moreover, the number of infiltrating CD8+ cells within 30µm from tumor cells was highest in OCSCC. Using scRNA-seq, we were able to annotate cell types and perform subclustering. This enabled us to distinguish among others CD8+ exhausted T cells.
Conclusions Our data indicate that, compared to other anatomical sites, oral cavity SCCs are more often populated by T cells. This suggests that particularly OCSCC may more easily respond to immunotherapy strategies aimed at activating T cells.
Disclosure Information T. Muijlwijk: None. C. Ballesteros-Merino: None. J.B. Poell: None. S.H. Ganzevles: None. C.R. Leemans: None. B.A. Fox: None. R.H. Brakenhoff: None. R. van de Ven: None.
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