CD274 and breast cancer: Concerning the PD-1/PD-L1 axis, PD-L1-bearing EV (PD-L1EV) derived from BC has the capacity to transfer functional active PD-L1 to other cells and to interact with PD-1 receptor, which results in the inhibition of T cell activation as well as T cell killing of BC cells (Yang et al. 2018).