To investigate the effects of hypoxia inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2(VEGFR2)、neuropilin -1(Nrp-1)expression on the proliferation of regulatory T Cells (Treg) in patients with non-small cell lung cancer (NSCLC).

All of 60 non-small cell patients (NSCLC) and 20 healthy people were enrolled and peripheral blood mononuclear cell (PBMC) were extracted. The content of CD4⁺ CD25⁺ FOXP3⁺ Treg cells in PBMC was detected by flow cytometry. The expression levels of HIF-1α, VEGF, transforming growth factor-β(TGF-β), Interleukin-2(IL-2) and interleukin-10(IL-10) in the supernatant of PBMC cells were detected by ELISA. The expression levels of VEGFR2 and Nrp-1 proteins in the supernatant of Treg cells were detected by Westernblotting, and the chemotaxis of VEGF to Treg cells was detected by transwell migration assay.

The proportion of CD4⁺ CD25⁺ FOXP3⁺ Treg cells in peripheral blood of patients with NSCLC was significantly higher than that of healthy control group (P<0.01). Compared with the normal group, the expression levels of HIF-1α, IL-10, TGF-β and VEGF in the NSCLC group were significantly increased (P<0.01), and the expression level of IL-2 was significantly decreased (P<0.01). The analysis of person correlation suggested that the content of Treg in PBMCs of patients with NSCLC was positively correlated with the expressions of HIF-1α, IL-10, TGF-β, and VEGF in the supernatant of PBMCs (r=0.74; r=0.73; r=0.68; r=0.58, all P<0.01), and negatively correlated with IL-2 expression (r=-0.59, P<0.01). The expression levels of VEGFR2 and Nrp-1 on the surface of Treg cells in patients with NSCLC were increased (P<0.01). VEGF showed a chemotactic effect on Treg cells, especially in the hypoxic state (P<0.01).

The hypoxia in NSCLC microenvironment induces the up-regulation of HIF-1α expression and the increased secretion of VEGF by tumor cells and endothelial cells. The recruitment and cell transformation promote the increase of Treg and the expression of surface receptor VEGFR2/Nrp-1, which leads to the accumulation and activation of Treg cells, Treg cells can stimulate the secretion of IL-2, IL-10, TGF-β, and then inhibit the effector cell function, leading to immune escape of lung cancer cells and progression of the disease.