PDCD1 and neoplasm: Moreover, immunocompetent orthotopic models also confirmed that co-treatment with Prdm1 overexpression and PD-1 mAb further impaired tumor proliferation compared with that in Prdm1 overexpression or PD-1 mAb treatment alone, whereas co-treatment with Prdm1 knockout and PD-1 mAb had a limited effect on tumor growth compared with that in Prdm1 knockout alone (Fig. 6c, d).