PDCD1 and melanoma: Research showed that probiotics could strengthen the efficacy of Immune checkpoint inhibitors such as programmed cell death 1 (PD-1) /programmed cell death ligand 1 (PD-L1) with Bifidobacterium strengthening the efficacy of anit-PD-1/PD-L1 on melanoma-bearing mice (Miller and Carson, 2020).