Here we investigated the anti-tumor effects on breast cancer cells of a novel anti-PD-L1 antibody, PD-L1_1, generated from a large repertoire of fully human antibodies specific for many T-cell immune checkpoints (ICs) obtained by phage display technology, and capable of inducing T cell activation, cytokine secretion and antitumor effects in vitro and in vivo9. The gene discussed is CD274; the disease is breast cancer.