Stromal and intratumoral T cell infiltration in head and neck squamous cell carcinoma

We investigated the prognostic significance of T cell infiltration in head and neck squamous cell carcinoma (HNSCC). Multichannel immunofluorescence staining was performed with fresh frozen tissue of 84 patients using antibodies against CD3, CD8, FoxP3 and cytokeratins. Thus, infiltration by cytotoxic T cells, T helper cells, and regulatory T cells into both the tumor stroma and epithelial tumor cell nests could be examined simultaneously in each tumor tissue. Evaluation of T cell infiltration was performed automated and computer-based with the StrataQuest software . Additionally, immunohistochemical p16 staining was performed. The tumor stroma was significantly more infiltrated by all T cell subtypes [cytotoxic T cells (CD3+CD8+FoxP3-), T helper cells (CD3+CD8-FoxP3-), regulatory T cells (CD3+CD8-FoxP3+)] than the tumor cell nests (p<0.001). T cell densities in tumor cell nests of p16 negative (n = 76) HNSCC were significantly lower than those of p16 positive (n = 8) tissues (p<0.01). For the p16-negative tumor tissues, the clinicopathological parameters of T and N stage were found to correlate with the T cell infiltration parameters. In univariate survival analysis of patients with p16-negative HNSCC, a higher percentage of regulatory T cells in the tumor stroma was associated with significantly better overall survival (OS) as well as progression-free survival (PFS, p>0.05). This association was also statistically significant in a multivariate Cox regression (hazard ratio for OS 2.7, p<0.05; hazard ratio for PFS = 2.3, p <0.05).