CD274 and neoplasm: have 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, leading to the dampening of T cell-mediated anti-tumor response, and the cytoplasmic domain of PD-L1 can trigger the signaling pathways involved in the cancerous transformation upon ligation with PD-1 fusion protein [4].