Exploring a Tumor-Intrinsic PD-L1 Signal with Proximity-Dependent Biotin Identification in Lung Cancer Cells

Blocking PD-L1/PD-1 interaction with antibody produces durable response in patients with diverse advanced cancers. However, it remains elusive on the engagement of PD-L1 to PD-1 leads to tumor-intrinsic signaling. In this study, we aim to explore novel protein(s) substrates which participating in transducing this tumor-intrinsic PD-L1 signaling. To this end, we performed a BioID (proximity-dependent Biotin IDentification) assay, in which we fused PD-L1 to BirA* (a promiscuous mutant of bacterial biotin ligase BirA) and overexpressed in a lung adenocarcinoma cell line A549. Through streptavidin affinity capture and mass spectrometry analysis, we identified 57 candidate proteins including 18 PD-L1/PD-1 interaction-dependent neighbors. In addition to this, 9 out of 57 candidates involve in EGFR signaling pathway, which is known to play a critical role in tumorigenesis and multiple therapeutic resistance of lung cancer. This study will provide a new insight in understanding tumor-intrinsic PD-L1 signaling eff...