PD-1/PD-L1 axis is one key therapeutic target against tumor cell immune escape. Structurally essential to the PD-1/PD-L1-linked immune escape is the binding interface of the PD-1/PD-L1 complex structure. Incorporating currently available PD-1/PD-L1-related experimental structures, this article unveils two sets of experimentally observed inter-molecular electrostatic interactions which stabilize the binding interface of the PD-1/PD-L1 complex structure. For the first time, this article proposes an evolutionary structural hypothesis that, as a result of natural selection, PD-1 is able to genetically mutate itself to structurally disrupt the PD-1/PD-L1 axis towards the restoration of T cell-mediated anti-tumor immunity.