To this end, we compared the immunogenic MC38 model, which bears a high tumor mutational burden (TMB),19 with the 9464D pediatric neuroblastoma model.20 21 Pediatric cancers represent a paradigm of immunologically cold tumors with a low mutational load, limited T-cell infiltration, and generally poor responsiveness to anti-PD-1/PD-L1.22 However, like many adult cancers, there is evidence of PD-1/PD-L1 expression in pediatric tumors,23 24 supporting the use of preclinical models to better understand how to target PD-1. This evidence concerns the gene CD274 and neuroblastoma.