In breast cancers, macrophages with PD-L1 and indolamine 2,3-dioxygenase (IDO) overexpression inhibited NK cell-mediated ADCC and T cell-mediated cytotoxicity after antibody-dependent cell phagocytosis (ADCP), thereby reducing the anti-tumor effects of monoclonal antibody therapy. This evidence concerns the gene IDO1 and neoplasm.