CD274 and neoplasm: However, since CSCs are usually located in deep tumour niche, the tumour microenvironment may protect CSCs from attack by anti-PD-L1 antibody and T cells [38] thus for an effective treatment, a delivery system will be necessary for breaking the barrier and delivering its therapeutic load; 2) Apart from cell surface, PD-L1 distributed in other cell compartments needs to be considered in the therapy, particularly these in cytoplasm and nucleus with possible different functions.