Reduction of myeloid-derived suppressor cells in peripheral blood by local hyperthermia in patients with advanced solid tumors.

Abstract

e21058 Background: Circulating levels of myeloid-derived suppressor cells (MDSCs) correlate with clinical cancer stage, metastatic tumor burden and tumor immune evasion. The potential contribution of MDSCs to thermotherapy has not been explored. The aim of this study was to investigate the impact of treatment of local hyperthermia on the levels of MDSCs in peripheral blood. Methods: Thirty patients with advanced solid tumors treated with local hyperthermia were enrolled. Peripheral blood samples were obtained before and after treatment immediately. Circulating MDSCs (identified as HLA-Dr-/low, CD11b+, CD33+ cells) were measured by flow cytometry. Meanwhile lymphocyte subpopulations in peripheral blood samples (T-helper-/T4-cells, T-suppressor-/T8-cells, natural-killer-/NK-cells, CD19+cells) were also analyzed using the same method. The association between MDSCs and the other lymphocyte subpopulation was examined by ultivariate linear regression analysis. Results: The percentage of MDSCs and other lymphocyte subpopulations before and after treatment are shown in the Table1. MDSCs were significantly reduced after local hyperthermia, so were the T-suppressor cells and the NK cells. But the T-helper cells and the ratio of T-helper/T-suppressor cells were increased. The numbers of CD3+ cells and CD19+ cells were not significantly affected by the treatment. This reduction of MDSCs is not associated with any other lymphocyte subtype. Conclusions: It was demonstrated that local hyperthermia can reduce abnormal accumulation of circulating MDSCs. The reduction of MDSCs was not associated with the other lymphocyte subpopulation. The percentage of MDSCs and lymphocyte subpopulations before and after treatment. MDSC CD3+CD4+ CD3+CD8+ CD4+/CD8+ CD3+ NK CD19+ B# 7.71±5.92 38.84±10.72 28.26±10.05 1.56±0.71 65.65±13.49 23.77±11.37 5.69±5.13 A* 6.45±4.85 43.80±10.89 26.92±9.93 1.98±1.26 68.80±14.23 19.37±10.58 6.37±6.25 P value 0.042 0.003 0.006 0.004 0.052 0.004 0.150 B# Before Local Hyperthermia. A* After Local Hyperthermia.