Increased prevalence of tumour infiltrating immune cells in oropharyngeal tumours in comparison to other subsites: relationship to peripheral immunity

The nature of the tumour microenvironment immune response in head and neck cancer patients has an important role in tumour development and metastasis, but it is unknown if this differs between cancer subsites or whether it is related to the peripheral immune response. Immune cells (CD4, CD8, Foxp3) in head and neck squamous cell carcinoma tissue (HNSCC; n = 66), detected by immunohistochemistry, have been correlated with tumour subsite and immune cells in the peripheral circulation (CD4(+)CD25(High)Foxp3(+) Treg and CD4(+) T cells), identified using flow cytometry. Oropharyngeal tumours had a greater number of infiltrating immune cells in both tumour and stroma compared with other subsites, but no difference was observed in the circulating levels. Immune cells in the stroma were positively related to those in the tumour with consistently higher levels in stroma. A strong relationship was found between the number of CD4(+) and Foxp3(+) cells but not between the number of CD8(+) and Foxp3(+) cells in the tumour. The number of Foxp3(+) cells within the tumour was positively correlated with the percentage of circulating CD4(+)CD25(High) cells positive for Foxp3. Late stage laryngeal tumours showed a higher number of Foxp3(+) lymphocytes compared with early stage malignancies, and oropharyngeal tumours had more CD4(+) cells in node negative tumours compared with node positive ones. The level of immune cell infiltration in head and neck squamous cell carcinoma appears to be subsite dependent residing primarily in the stroma and is likely to be dependent on the peripheral immune response.