PDCD1 and neuroblastoma: To determine whether inducing MMR deficiency in neuroblastoma sensitizes such tumors to anti-PD1, as shown in other adult malignancies, we treated both pMMR and idMMR neuroblastoma tumor-bearing mice with anti-PD1 when tumors became palpable (∼day 10) and assessed the toxicity of the treatment and found no significant changes in mouse body weight (Figures 3A and S5A).