PDCD1 and cancer: While blockading CCR8 on ti-Tregs in tumors in murine cancer models did not improve therapeutic outcomes of anti-PD-1 therapy, depletion of CCR8+ ti-Tregs with natural killer (NK) cells in antibody dependent cellular cytotoxicity (ADCC)-capable mice demonstrated synergistic tumor regression with anti-PD-1 ICI (10).