Mechanism of human leukocyte antigen-G inhibiting T cell immune function in triple-negative breast cancer

Objective To investigate the mechanism of human leukocyte antigen-G (HLA-G) expression and T cells activation in triple-negative breast cancer(TNBC) cells to exert immunosuppressive function. Methods From three groups of breast cancer cell lines（MDA-MB-231，HCC1937， MDA-MB-468）,real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot were detected and screened that the breast cancer cell line was HCC1937,which with high expression of HLA-G, and low expression of fibrinogen-like protein 1 (FGL1), programmed death factor ligand 1 (PD-L1), as well as sialic acid-binding immunoglobulin-like lectin 15 (SIGLEC15) . HCC1937 cells were divided into NC group (control group) and KD group (knockdown group), and RNA interference (RNAi) lentiviral vectors were constructed and transfected into KD cells to knock down HLA-G gene, and the verification was carried out. HCC1937 cells were treated with HLA-G antibody blocking/nonblocking, and Jurkat cells were treated with CD3 and CD28 activation/non-activation, respectively, and the two types of cells were co-cultured into 8 groups: NC^--, KD^--, NC^+-, KD^+-, NC^-+, KD^-+, NC⁺⁺, and KD⁺⁺ groups. Cell scratch assay, MTT and ELISA method were used to detect cell migration rate, proliferation rate, and interferon (IFN)-γ and interleukin (IL)-2 levels in cell supernatants, respectively. Results RT-qPCR showed that the HLA-G gene was successfully knocked down in HCC1937 cells. Compared with the NC⁺⁺ group, the migration rate of the KD⁺⁺ group was significantly increased (P＜0.05), but there was no statistical difference in the cell proliferation rate between each pair of co-culture groups (P＞0.05). The concentration of IFN-γ in the KD⁺⁺ group was lower than that in the NC⁺⁺ group and the NC^-+ group (P＜0.05), but there was no significant difference in the concentration of IL-2 between each pair of co-culture groups (P＞0.05). Conclusion HLA-G in TNBC cells may promote the secretion of IFN-γ by activing T cells, and IFN-γ can inhibit the immune function of T cells and promote tumor metastasis after HLA-G decreased."