Immune checkpoint blockade in human cancer therapy: lung cancer and hematologic malignancies

Tumor immune evasion is one of the hallmarks of cancer, and expression of the B7 family of immune checkpoints (PD-L1, PD-L2, B7-H3, B7x and HHLA2) is one mechanism of immune evasion by tumors to suppress T-cell function. Antibodies blocking these interactions of B7-1/B7-2/CTLA-4 and PD-L1/PD-L2/PD-1 have had remarkable clinical success in several cancers and are less toxic than traditional chemotherapy. Even though only a small proportion of patients respond to checkpoint blockade, the duration of such responders due to immunological memory is remarkable and is longer than would be expected with any other agent in refractory disease. In this article, we review the therapeutic trials of blocking these pathways in human lung cancer and hematological malignancies.