PDCD1 and neoplasm: A recent study reported that VISTA expression is upregulated in myeloid cells after treatment with anti-CTLA-4 antibody (ipilimumab) and might promote resistance to CTLA-4 blockade.47 Although it remains unknown whether anti-PD-1 antibody treatment also upregulates VISTA expression in the tumour microenvironment, resistance to anti-PD-1 therapy is a major problem that must be solved to advance to the next stage of cancer immunotherapy.