T cell proliferation was inhibited by co-culture with MDA-MB-231, T47D, MCF-7, and MDA-MB453 breast cancer cell lines producing sPD-L1, whereas sPD-L1 could effectively restore the inhibitory effect of PD-1/PD-L1 on T lymphocytes after the addition of anti-PD-L1 antibody (atezolizumab). Here, CD274 is linked to breast carcinoma.