CD45RA-Foxp3high but not CD45RA+ Foxp3low suppressive T regulatory cells increased in the peripheral circulation of patients with head and neck squamous cell carcinoma and correlated with tumor progression

Background: T regulatory cells (Tregs) contribute to the progression of head and neck squamous cell carcinoma (HNSCC) by suppressing antitumor immunity. However, little is known regarding the functional heterogeneity of Tregs in HNSCC patients. Methods: Using multicolor flow cytometry, the frequency of three Treg subsets, separated on the basis of CD45RA and Foxp3, from the peripheral circulation of newly-presenting HNSCC patients (19 oral cavity squamous cell carcinoma, 20 hypopharyngeal squamous cell carcinoma, 18 nasopharyngeal squamous cell carcinoma, 19 oropharyngeal squamous cell carcinoma, and 36 laryngeal squamous cell carcinoma) were assessed with regard to 31 healthy donors and clinicopathological features. Moreover, the functional capacity of each Treg subsets was evaluated based on CD45RA and CD25 expression. Results: The frequency of Tregs in the peripheral circulation of HNSCC patients as a whole cohort was higher than in healthy donors (P < 0.0001). However, the frequency of Tregs was similar between patients with oral cavity squamous cell carcinoma and healthy donors (P = 0.269). Further dividing Tregs into three subsets based on Foxp3 and CD45RA expression revealed that the frequency of CD45RA(-)Foxp3(high) Tregs and CD45RA(-)Foxp3(low)CD4(+) T cells in patients with HNSCC developing from different subsites was higher than in healthy donors (P < 0.0001, P < 0.0001), whereas the frequency of CD45RA(+) Foxp3(low) Tregs was lower than in healthy donors (P < 0.0001). Functionally study revealed that CD45RA(-)CD25(+++) Tregs significantly inhibit the proliferation of CD4(+) CD25-T cells (P < 0.001) and secrete lower levels of cytokines (P < 0.01) compared with CD45RA(-)CD25(++) CD4(+) T cells. Importantly, the frequency of CD45RA(-)Foxp3(high) Tregs positively correlate with tumor stage (P < 0.0001) and nodal status (P < 0.0001). Conclusions: CD45RA(-)Foxp3(high) Tregs increase in the peripheral circulation of HNSCC patients, and correlate with tumor stage and nodal status; suggesting a role in tumor progression which may be manipulated by future immunotherapy.