Identification and characterization of an alternative cancer-derived PD-L1 splice variant

Cancer Immunol Immunother. 2019 Mar;68(3):407-420. doi: 10.1007/s00262-018-2284-z. Epub 2018 Dec 18.


Therapeutic blockade of the PD-1/PD-L1 axis is recognized as an effective treatment for numerous cancer types. However, only a subset of patients respond to this treatment, warranting a greater understanding of the biological mechanisms driving immune evasion via PD-1/PD-L1 signaling and other T-cell suppressive pathways. We previously identified a head and neck squamous cell carcinoma with human papillomavirus integration in the PD-L1 locus upstream of the transmembrane domain-encoding region, suggesting expression of a truncated form of PD-L1 (Parfenov et al., Proc Natl Acad Sci USA 111(43):15544-15549, 2014). In this study, we extended this observation by performing a computational analysis of 33 other cancer types as well as human cancer cell lines, and identified additional PD-L1 isoforms with an exon 4 enrichment expressed in 20 cancers and human cancer cell lines. We demonstrate that cancer cell lines with high expression levels of exon 4-enriched PD-L1 generate a secreted form of PD-L1. Further biochemical studies of exon 4-enriched PD-L1 demonstrated that this form is secreted and maintains the capacity to bind PD-1 as well as to serve as a negative regulator on T cell function, as measured by inhibition of IL-2 and IFNg secretion. Overall, we have demonstrated that truncated forms of PD-L1 exist in numerous cancer types, and have validated that truncated PD-L1 can be secreted and negatively regulate T cell function.

Keywords: Cancer immunology; HPV; PD-L1; Secreted PD-L1.

MeSH terms

  • Alternative Splicing*
  • B7-H1 Antigen / genetics*
  • Cell Line, Tumor
  • Exons
  • Humans
  • Interferon-gamma / antagonists & inhibitors
  • Lymphokines / pharmacology
  • Protein Isoforms / blood
  • Protein Isoforms / isolation & purification


  • B7-H1 Antigen
  • Lymphokines
  • Protein Isoforms
  • interleukin 2 inhibitor
  • Interferon-gamma