Spatial Distribution and Prognostic Value of T Cell Subtypes and Immune Biomarkers in p16-Negative HNSCC

Patients with head and neck squamous cell carcinoma (HNSCC) suffer from severe morbidity and mortality. Immunotherapy represents a novel promising treatment option. Therefore, a better understanding of the immune niche is needed. This study focuses on the spatial distribution and prognostic value of different T cell subtypes in 84 HNSCC specimens as well as chemokine and cytokine levels associated with spatial T cell infiltration. Density of T helper (T_H), cytotoxic (CTL), and regulatory T cells (T_reg) was quantified by multicolor tissue cytometry on a single cell level in whole tissue sections, discriminating between T cells located in epithelial tumor cell nests or tumor stroma, respectively. In addition, quantitative levels of 27 immune-related factors were assessed. Survival analysis of patients with p16-negative HNSCC revealed higher stromal T_reg densities to be an independent prognostic factor for better progression-free and overall survival. Furthermore, high levels of CXCL10, IL-9, and CCL4 were associated with significantly higher numbers of T cells, especially for CTL with direct contact to tumor cells, whereas for VEGF the opposite effect was observed in the tumor stroma. In conclusion, T_reg cell infiltration as well as distinct cytokine levels could serve as new immune biomarkers in p16-negative HNSCC to predict survival and the spatial distribution of T cells.