PD-L1 is upregulated by EBV-driven LMP1 through NF-κB pathway and correlates with poor prognosis in natural killer/T-cell lymphoma

J Hematol Oncol. 2016 Oct 13;9(1):109. doi: 10.1186/s13045-016-0341-7.


Background: Natural killer/T-cell lymphoma (NKTCL) is an Epstein-Barr virus (EBV)-associated, highly aggressive lymphoma. Treatment outcome remains sub-optimal, especially for advanced-stage or relapsed diseases. Programmed cell death receptor 1 (PD-1) and PD ligand 1 (PD-L1) have become promising therapeutic targets for various malignancies, but their role in the pathogenesis and their interactions with EBV in NKTCL remains to be investigated.

Methods: Expression of PD-L1 was measured in NK-92 (EBV-negative) and SNK-6 (EBV-positive) cells by western blot, quantitative real-time PCR and enzyme-linked immunosorbent assay, and flow cytometry, respectively. Latent membrane protein 1 (LMP1)-harboring lentiviral vectors were transfected into NK-92 cells to examine the correlation between LMP1 and PD-L1 expression. Proteins in the downstream pathways of LMP1 signaling were measured in NK-92 cells transfected with LMP1-harboring or negative control vectors as well as in SNK-6 cells. PD-L1 expression on tumor specimens and serum concentration of soluble PD-L1 were collected in a retrospective cohort of patients with Ann Arbor stage I~II NKTCL, and their prognostic significance were analyzed.

Results: Expression of PD-L1 was significantly higher in SNK-6 cells than in NK-92 cells, at both protein and mRNA levels. Expression of PD-L1 was remarkably upregulated in NK-92 cells transfected with LMP1-harboring lentiviral vectors compared with those transfected with negative control vectors. Proteins in the MAPK/NF-κB pathway were upregulated in LMP1-expressing NK-92 cells compared with the negative control. Selective inhibitors of those proteins induced significant downregulation of PD-L1 expression in LMP1-expressing NK-92 cells as well as in SNK-6 cells. Patients with a high concentration of serum soluble PD-L1 (≥3.4 ng/ml) or with a high percentage of PD-L1 expression in tumor specimens (≥38 %) exhibited significantly lower response rate to treatment and remarkably worse survival, compared with their counterparts. A high concentration of serum soluble PD-L1 and a high percentage of PD-L1 expression in tumor specimens were independent adverse prognostic factors among patients with stage I~II NKTCL.

Conclusions: PD-L1 expression positively correlated LMP1 expression in NKTCL, which was probably mediated by the MAPK/NF-κB pathway. PD-L1 expression in serum and tumor tissues has significant prognostic value for early-stage NKTCL.

Keywords: Epstein–Barr virus; Latent membrane protein 1; Natural killer/T-cell lymphoma; Programmed cell death receptor 1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • B7-H1 Antigen / analysis*
  • B7-H1 Antigen / blood
  • Biopsy
  • Cells, Cultured
  • Female
  • Gene Expression Regulation, Neoplastic
  • Herpesvirus 4, Human
  • Host-Pathogen Interactions
  • Humans
  • Lymphoma, Extranodal NK-T-Cell / diagnosis*
  • Lymphoma, Extranodal NK-T-Cell / pathology
  • Lymphoma, Extranodal NK-T-Cell / virology
  • Male
  • Middle Aged
  • NF-kappa B / metabolism*
  • Prognosis
  • Transfection
  • Viral Matrix Proteins / genetics
  • Viral Matrix Proteins / physiology*


  • B7-H1 Antigen
  • CD274 protein, human
  • EBV-associated membrane antigen, Epstein-Barr virus
  • NF-kappa B
  • Viral Matrix Proteins