R404 – Regulatory T Cells and Clinical Outcome in HNSCC Patients
Problem To determine the correlation between peripheral blood CD4+CD25high regulatory T cells (Treg), a suppressor cell population that dampen the immune response, and clinical outcome and survival in HNSCC patients. Methods Treg cell numbers in the peripheral blood of newly-presenting, untreated HNSCC patients (n=65) were determined pre-operatively, 4–6 weeks after treatment (n=30) and in a cohort of healthy controls (n=35) of similar age and sex, after Treg cell isolation using magnetic microbeads (Miltenyi Biotec) by flow cytometry. The Mann-Whitney U test was used to analyse the correlations between Treg cell levels and clinical outcome. Results Treg cells were significantly higher in patients pre-operatively vs. controls (p=0.002). After treatment, patients showed a significant rise compared with their pre-treatment levels (p=0.022). Pre-treatment Treg cells levels did not correlate with survival or any of the other conventional clinicopathological parameters. However, higher Treg cells levels were discovered in the advanced disease stages (III/IV vs. I/II, median 6.3 vs 4.3) in the pre-treatment group that turned into significantly higher levels in the early disease stages post treatment (I/II vs. III/IV, median 10.8 vs. 5.67 p=0.044). Conclusion Although peripheral blood Treg cells levels were higher in patients when compared to controls, no correlation was found between this cell population and clinical outcome or survival. In contrast with gastric, colorectal and ovarian tumors, Treg cell levels did not normalize 4–6 weeks after curative treatment in this cohort of HNSCC patients. Studies into Treg cell function are thus required to try and elucidate the apparent paradox in Treg cell levels observed in HNSCC. Significance The presence of Regulatory T cells in the peripheral blood of HNSCC patients may be detrimental to host defence against tumor. Further studies are needed to explore their role in the tumor microenvironment and their correlation with clinical outcome.