PDCD1 and colon adenocarcinoma: MLKL deficiency in CT26 colon adenocarcinoma (without expression of an artificial antigen such as OVA) also resulted in strongly impaired antitumor activity of combined anti-PD-1/CTLA-4 ICI immunotherapy in tumor-bearing BALB/c mice (figure 1G and online supplemental figure S2A–B, ).