CD274 and neoplasm: Azuma et al. have first established the theory that PD-L1 can serve as a bidirectional regulator, the extra-cellular domain of PD-L1 can interact with its receptor PD-1 on T cells, resulting in dampening T-cell mediated anti-tumor response, and the cytoplasmic domain of PD-L1 can also trigger the cellular signaling pathways involved in the anti-apoptosis via ligation with PD-1 fusion protein [4].