In the current study using the CD127low/− Treg cell phenotype, no difference in the frequency between subsites was observed, and the suppressive activity of these circulating Treg cells was not affected by primary tumour location. Although tumour subsite had no influence on the level of Treg cells, the HNSCC patients with advanced stage tumours and those that metastasized to the lymph nodes had significantly increased levels of CD25high Treg cells
in comparison to patients with early stage tumours and no nodal involvement, respectively; this BMN 673 clinical trial contrasts with previous HNSCC studies, which found no differences.[12, 30-32] Again, this is hypothesized to be due to the different phenotypes used to identify Treg cells and/or the composition of the patient cohorts. Furthermore, in other cancer types, patients
with advanced stage tumours and those whose disease has spread to the lymph nodes have been reported to harbour an increased frequency of circulating Treg cells in comparison to patients with early stage tumours and no nodal involvement.[15, 29, 33, 34] It remains unclear, however, whether the presence of the regulatory population promotes the growth and spread of the tumour or whether Selleck Dabrafenib these aspects cause an elevation in Treg cell frequency. Studies reporting an increase in the frequency of Treg cells in the peripheral circulation of cancer patients have postulated that this is partly responsible for the suppression of the host’s anti-tumour response. Although this may well be the case, it is also important to assess the functional activity of these cells by examining the level of suppression induced on the proliferation of effector T cells. Two effector T-cell populations were investigated, consisting of the classic CD4+ CD25− population (CD4+
CD25− CD127−/+), frequently used by research groups to assess the suppressive activity of Treg cells[12, 28, 35] and a population of activated T cells expressing the IL-7 receptor α chain, CD4+ CD25+ CD127+. The current study assessed the level of suppression induced at four different Treg : effector T-cell ratios and in agreement with previous PAK6 publications,[12, 17] the proliferation of effector T cells (CD4+ CD25− CD127−/+ and CD4+ CD25+ CD127+) was inhibited in the presence of Treg cells (CD4+ CD25inter CD127low/− and CD4+ CD25high CD127low/−) in a ratio-dependent manner. Although the choice of ratios varies between studies the 1 : 1 ratio is predominately employed,[12, 17] therefore in accordance with this, all suppression experiments in the current study were performed at the 1 : 1 ratio, and the results from these experiments were used for comparison.