A previous report described that PD-L1 administration did not have curative effect on 90% of MC38-CEA tumor-bearing mice and 100% of 4T1 tumor-bearing mice that were treated.7 Immune-inflamed tumors, also called ‘hot’ tumors, respond better to checkpoint blockade compared with ‘cold’ tumors wherein T cells are absent or excluded.1 2 To determine whether the differential response in the MC38-CEA and 4T1 tumor models may be associated with a variance in immune infiltrates, flow cytometry (figure 1A) and immunofluorescence (IF) microscopy (figure 1B) were performed. Here, CEACAM5 is linked to neoplasm.