Exosomal programmed cell death 1 ligand 1 (PD-L1) (exoPD-L1)

Exosomal programmed cell death 1 ligand 1 (exoPD-L1) is a specialized form of the PD-L1 protein that is secreted by tumor cells on the surface of small extracellular vesicles known as exosomes (Chen et al., 2018, Nature). This secreted form of PD-L1 plays a pivotal role in mediating systemic immunosuppression by traveling through the circulatory system to interact with immune cells in lymphoid organs or other distant sites (Poggio et al., 2019, Cell). Upon reaching its destination, exoPD-L1 binds to the Programmed cell death 1 (PD-1) receptor on the surface of T-cells, inducing a state of exhaustion and preventing the immune system from mounting an effective attack against the tumor (Yang et al., 2021, Molecular Cancer). Unlike the membrane-bound PD-L1 found directly on the surface of tumor cells, exoPD-L1 allows for immune evasion even when the tumor and immune cells are not in direct physical contact (Daassi et al., 2020, Journal of Extracellular Vesicles). Clinically, the levels of exoPD-L1 in a patient's blood serve as a critical biomarker for predicting the efficacy of immune checkpoint inhibitors and monitoring the progression of various cancers, including melanoma and lung cancer (Cordonnier et al., 2020, Cancers). Therapeutic interventions primarily involve monoclonal antibodies such as atezolizumab or durvalumab, which block the PD-L1/PD-1 interaction to restore T-cell function (Kim et al., 2019, Experimental & Molecular Medicine). However, high circulating levels of exoPD-L1 are frequently associated with primary or acquired resistance to these therapies, presenting a significant challenge in clinical oncology (Xie et al., 2019, Journal of Hematology & Oncology).

Other names

CD274B7-H1PDCD1L1Programmed death-ligand 1Exosomal PD-L1B7 homolog 1

Exosomal PD-L1 binds to the PD-1 receptor on T-cells, triggering inhibitory signaling pathways that lead to T-cell exhaustion and the suppression of anti-tumor immune responses.