Targeting PD-1/PD-L1 in cancer immunotherapy: An effective strategy for treatment of triple-negative breast cancer (TNBC) patients.

Maintaining the balance between eliciting immune responses against foreign proteins and tolerating self-proteins is crucial for maintenance of homeostasis. The functions of programmed death protein 1 (PD-1) and its ligand programmed death ligand 1 (PD-L1) are to inhibit immune responses so that over-reacting immune cells does not cause any damage to its own body cells. However, cancer cells hijack this mechanism to attenuate immune cells functions and create an immunosuppressive environment that fuel their continuous growth and proliferation.