The programmed death ligand 1 interactome demonstrates bidirectional signaling coordinating immune suppression and cancer progression in head and neck squamous cell carcinoma

J Natl Cancer Inst. 2023 Nov 8;115(11):1392-1403. doi: 10.1093/jnci/djad126.


Background: The programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) are validated cancer targets; however, emerging mechanisms and impact of PD-L1 intracellular signaling on cancer behavior are poorly understood.

Methods: We investigated the cancer cell intrinsic role of PD-L1 in multiple patient-derived models in vitro and in vivo. PD-L1 overexpression, knockdown, and PD-L1 intracellular domain (PD-L1-ICD) deletion (Δ260-290PD-L1) models were assessed for key cancer properties: clonogenicity, motility, invasion, and immune evasion. To determine how PD-L1 transduces signals intracellularly, we used the BioID2 platform to identify the PD-L1 intracellular interactome. Both human papillomavirus-positive and negative patient-derived xenografts were implanted in NOD-scid-gamma and humanized mouse models to investigate the effects of recombinant PD-1, anti-PD-L1, and anti-signal transducer and activator of transcription 3 (STAT3) in vivo.

Results: PD-L1 intracellular signaling increased clonogenicity, motility, and invasiveness in multiple head and neck squamous cell carcinoma (HNSCC) models, and PD-1 binding enhanced these effects. Protein proximity labeling revealed the PD-L1 interactome, distinct for unbound and bound PD-1, which initiated cancer cell-intrinsic signaling. PD-L1 binding partners interleukin enhancer binding factors 2 and 3 (ILF2-ILF3) transduced their effect through STAT3. Δ260-290PD-L1 disrupted signaling and reversed pro-growth properties. In humanized HNSCC in vivo models bearing T-cells, PD-1 binding triggered PD-L1 signaling, and dual PD-L1 and STAT3 inhibition were required to achieve tumor control.

Conclusions: Upon PD-1 binding, the PD-L1 extracellular and intracellular domains exert a synchronized effect to promote immune evasion by inhibiting T-cell function while simultaneously enhancing cancer cell-invasive properties.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • B7-H1 Antigen*
  • Head and Neck Neoplasms* / genetics
  • Humans
  • Mice
  • Mice, Inbred NOD
  • Programmed Cell Death 1 Receptor
  • Squamous Cell Carcinoma of Head and Neck / genetics


  • B7-H1 Antigen
  • CD274 protein, human
  • Programmed Cell Death 1 Receptor
  • PDCD1 protein, human