On the basis of these considerations and of the results relative to the anti-tumor efficacy of the novel isolated PD-L1_1 mAb, we investigated the inhibitory effects of PD-L1_1 on tumor cells in combinatorial treatments with the anti-ErbB2 antibody, Erb-hcAb, capable of inhibiting tumor cell growth in vitro and in vivo21. The gene discussed is ESR2; the disease is neoplasm.