Effect of TGF-β1 on blood CD4+CD25high regulatory T cell proliferation and Foxp3 expression during non-small cell lung cancer blood metastasis.

Metastatic circulating tumor cells in non-small cell lung cancer (NSCLC) metastasis have been reported to be associated with an immune response. The present study aimed to provide a theoretical basis for the immunomodulatory processes during NSCLC blood metastasis. NSCLC blood and normal peripheral blood mononuclear cells (PBMCs) were collected. The quantity of cluster of differentiation (CD)4+CD25high regulatory T (Treg) cells and the intracellular forkhead box protein 3 (Foxp3) expression in CD4+CD25high Treg cells were determined by flow cytometry. Furthermore, the effect of transforming growth factor β1 (TGF-β1) on NSCLC blood CD4+CD25+ Treg cell proliferation was explored by activating blood mononuclear cells with an anti-CD3 monoclonal antibody, interleukin-2 and different doses of TGF-β1. Reverse transcription-quantitative polymerase chain reaction assays were used to detect the mRNA expression of Foxp3. Carboxyfluorescein succinimidyl ester staining was used to analyze the proliferation dynamics of lymphocyte subsets. Results indicate that the proportion of CD4+ T cells in the blood of patients with NSCLC was significantly higher compared with normal peripheral blood (P<0.01). Foxp3 expression in NSCLC blood Treg cells was significantly decreased compared with normal peripheral blood (P<0.01). NSCLC blood mononuclear cells treated with TGF-β1 at 1, 5 and 25 ng/ml significantly induced Foxp3 expression in CD4+CD25+ Treg cells compared with the control group (P<0.05). The proportion of CD4+CD25+ Treg and CD8+ T cells were elevated in generation 6, 7, 8 after 6 days of TGF-β1 treatment compared with untreated cells. The proportion of CD4+CD25+ Treg and CD8+ T cells were elevated in generation 8, 9 and with TGF-β1 treatment after 8 days compared with untreated cells. These results indicate that CD4+CD25+ Treg cells proliferate at a greater rate compared with CD8+ T cells after 4, 6 or 8 days of treatment. The proportion of CD4+CD25high Treg cells in NSCLC blood was significantly higher (P<0.05) compared with normal peripheral blood. The number of Foxp3+ T cells was significantly lower (P<0.05) compared with normal peripheral blood. The data presented in this study suggest that NSCLC blood CD4+CD25high Treg cells are functionally immature and that TGF-β1 may promote maturation.