PDCD1 and neoplasm: The diversity of immune checkpoint inhibitors to different molecular targets on tumor cells and immune cells is growing and is currently being investigated in several clinical trials in GC: the anti-PD-1 antibodies nivolumab, pembrolizumab, sintilimab, tislelizumab, retifanlimab and tebotelimab (T-cells), as well as the anti-PD-L1 antibodies atezolizumab, avelumab, durvalumab, retifanlimab, tebotelimab (cancer cells, dendritic cells) and the anti-CTLA-4 antibody ipilimumab (T-cells).