Although expression of Ctla-4 was hardly induced by trAbs on total Cd3+ cells in the tumor, there is a chance to further improve efficacy of our combination therapy of tumor vaccination and SUREK trAb by inhibiting Tregs by CTLA-4 immune checkpoint blockade as the combination with the checkpoint inhibitor anti-CTLA-4 proved to be superior to anti-PD-1 monotherapy in a preclinical neuroblastoma model (39). This evidence concerns the gene PDCD1 and neuroblastoma.