PD-1/PD-L1 checkpoint blockade in immune-antitumortherapy:advances and perspectives

During the past three decades,studies have shown that tumor cells could"manipulate"host immunity to escape the immune defenses in the tumor microenvironment.One of the most important underlying mechanisms is immune-suppression regulated by programmed cell death-1 or its ligand 1(PD-1/PD-L1),which makes PD-1/PD-L1 blockadea promising target of cancer immune-therapy.Tumors could suppress immuno-response of T cells by activating PD-1/PD-L1 signaling pathway.Therefore,inhibiting the interaction between PD-1 and PD-L1 could reconstitute the enduring antitumor immunity in the tumor microenvironment via enhancing the T-cell response,there after augmenting the endogenous antitumor force of the immune system.Along these lines,inhibitors of PD-1/PD-L1 has been applied in multiple clinical trials against various types of tumors.Recent studies indicated that PD-1/PD-L1 blockade have demonstrated high efficacy and safety against melanoma,lung,kidney and several other solid tumors,as well as hematological malignancies.Nevertheless,the efficacy of this checkpoint blockade approach is not universal.Some investigation suggested that lack of responses to anti-PD-1/PD-L1 therapy of patients without PD-1/PD-L1 over-expression was expected.In this review,we summarize the history and current understanding of multiple intrinsic and extrinsic mechanisms via which PD-1/PD-L1 is regulated and research advances in preclinical/clinical aspects of PD-1/PD-L1,as well as significance and perspectives regarding the PD-1/PD-L1 blockade in immune-antitumor therapy.