Effects of the microenvironment of irradiated tumor cells on Treg cells and related regulation factors

Objective To explore the immune tolerance in tumor microenvironment, we detected the expressions of CD receptors and related cytokines in Treg cells after being co-cultured with irradiated lung cancer cells. Methods Lymphocytes were isolated from human peripheral blood and cultured with lung adenocarcinoma cells A549, after irradiation with 6 Gy X-rays, the expression of CD4+ CD25+, CD4+ CD25+ FoxP3+, CD4+ CD25+ NrP1+ and ICOS, CTLA-4 in the lymphocytes were tested by flow cytometry, and the contents of IL-10, TGF-β and IL-17 in the supernatant were detected by ELISA. Results Compared with lymphocytes alone culture, the expressions of CD4+ CD25+, CD4+ CD25+ FoxP3+, CD4+ CD25+ NrP1+, ICOS, CTLA-4, IL-10 and TGF-β in the co-culture groups with and without irradiation were all increased (t=2.78-40.61, P<0.05), the CD4+ CD25+ and CTLA-4 in the lymphocytes were increased after irradiation (t=2.96, 2.94, 4.47, 2.77, P<0.05). The content of IL-17 in the supernant were increased after co-cuture with irradiated A549 cells (t=4.00, 4.71, P<0.05), but it had no obvious changes after irradiation alone. Conclusions The immune tolerance of lung cancer cells microenvironment under irradiation might contribute to the up-promotion of CD4+ CD25+ Treg cells, CTLA-4 and IL-17 although the molecular mechanisms still need to be further investigated. Key words: Radiation; A549 cell line; Tumor microenvironment; Regulatory T cells; Immune tolerance