Intratumoral regulatory T cells upregulate immunosuppressive molecules in head and neck cancer patients

Abstract

Background:Although regulatory T cells (Treg) are highly enriched in human tumours compared with peripheral blood, expression of the immune-checkpoint receptors, immunosuppressive molecules and function of Treg in these two sites remains undefined.Methods:Tumour-infiltrating lymphocytes and peripheral blood lymphocytes were isolated from a cohort of head and neck squamous cell carcinoma (HNSCC) patients. The immunosuppressive phenotypes and function of intratumoral Treg were compared with those of peripheral blood Treg.Results:The frequency of immune-checkpoint receptor-positive cells was higher on intratumoral FOXP3 + CD25 hi Treg compared with circulating Treg (CTLA-4, P=0.002; TIM-3, P=0.002 and PD-1, P=0.002). Immunosuppressive effector molecules, LAP and ectonucleotidase CD39 were also upregulated on intratumoral FOXP3+ Treg (P=0.002 and P=0.004, respectively). CTLA-4 and CD39 were co-expressed on the majority of intratumoral FOXP3+ CD4+ Treg, suggesting that these molecules have a key role in regulatory functions of these cells in situ. Notably, intratumoral Treg exhibited more potently immunosuppressive activity than circulating Treg.Conclusion:These results indicate that intratumoral Treg are more immunosuppressive than circulating Treg and CTLA-4 and CD39 expressed can be potential target molecules to inhibit suppressive activities of intratumoral Treg in situ. © 2013 Cancer Research UK. All rights reserved.