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      Abundant PD-L1 expression in Epstein-Barr Virus-infected gastric cancers

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          Abstract

          Gastric cancer (GC) is a deadly disease with limited treatment options. Recent studies with PD-1 inhibition have shown promising results in GC, but key questions remain regarding which GC subclass may respond best. In other cancers, expression of the PD-1 ligand PD-L1 has been shown to identify cancers with greater likelihood of response to PD-1 blockade. We here show with immunohistochemistry that Epstein-Barr Virus (EBV)+ GCs ( n = 32) have robust PD-L1 expression not seen in other GCs. In EBV+ GC, we observed PD-L1 staining in tumor cells in 50% (16/32) and immune cells in 94% (30/32) of cases. Among EBV-negative GCs, PD-L1 expression within tumors cells was observed only in cases with microsatellite instability (MSI), although 35% of EBV-/MSS GCs possessed PD-L1 expression of inflammatory cells. Moreover, distinct classes of GC showed different patterns of PD-L1+ immune cell infiltrations. In both EBV+ and MSI tumors, PD-L1+ inflammatory cells were observed to infiltrate the tumor. By contrast, such cells remained at the tumor border of EBV-/MSS GCs. Consistent with these findings, we utilized gene expression profiling of GCs from The Cancer Genome Atlas study to demonstrate that an interferon-γ driven gene signature, an additional proposed marker of sensitivity to PD-1 therapy, were enriched in EBV+ and MSI GC. These data suggest that patients with EBV+ and MSI GC may have greater likelihood of response to PD-1 blockade and that EBV and MSI status should be evaluated as variables in clinical trials of these emerging inhibitors.

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          Most cited references 17

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          Quantitative Assessment of the Heterogeneity of PD-L1 Expression in Non-Small-Cell Lung Cancer.

          Early-phase trials with monoclonal antibodies targeting PD-1 (programmed cell death protein 1) and PD-L1 (programmed cell death 1 ligand 1) have demonstrated durable clinical responses in patients with non-small-cell lung cancer (NSCLC). However, current assays for the prognostic and/or predictive role of tumor PD-L1 expression are not standardized with respect to either quantity or distribution of expression.
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            PD-L1/B7H-1 inhibits the effector phase of tumor rejection by T cell receptor (TCR) transgenic CD8+ T cells.

            Although increased circulating tumor antigen-specific CD8(+) T cells can be achieved by vaccination or adoptive transfer, tumor progression nonetheless often occurs through resistance to effector function. To develop a model for identifying mechanisms of resistance to antigen-specific CTLs, poorly immunogenic B16-F10 melanoma was transduced to express the K(b)-binding peptide SIYRYYGL as a green fluorescent protein fusion protein that should be recognized by high-affinity 2C TCR transgenic T cells. Although B16.SIY cells expressed high levels of antigen and were induced to express K(b) in response to IFN-gamma, they were poorly recognized by primed 2C/RAG2(-/-) T cells. A screen for candidate inhibitory ligands revealed elevated PD-L1/B7H-1 on IFN-gamma-treated B16-F10 cells and also on eight additional mouse tumors and seven human melanoma cell lines. Primed 2C/RAG2(-/-)/PD-1(-/-) T cells showed augmented cytokine production, proliferation, and cytolytic activity against tumor cells compared with wild-type 2C cells. This effect was reproduced with anti-PD-L1 antibody present during the effector phase but not during the priming culture. Adoptive transfer of 2C/RAG2(-/-)/PD-1(-/-) T cells in vivo caused tumor rejection under conditions in which wild-type 2C cells or CTLA-4-deficient 2C cells did not reject. Our results support interfering with PD-L1/PD-1 interactions to augment the effector function of tumor antigen-specific CD8(+) T cells in the tumor microenvironment.
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              Constitutive AP-1 activity and EBV infection induce PD-L1 in Hodgkin lymphomas and posttransplant lymphoproliferative disorders: implications for targeted therapy.

              Programmed cell death ligand 1 (PD-L1) is a molecule expressed on antigen-presenting cells that engages the PD-1 receptor on T cells and inhibits T-cell receptor signaling. The PD-1 axis can be exploited by tumor cells to dampen host antitumor immune responses and foster tumor cell survival. PD-1 blockade has shown promise in multiple malignancies but should be directed toward patients in whom it will be most effective. In recent studies, we found that the chromosome 9p24.1 amplification increased the gene dosage of PD-L1 and its induction by JAK2 in a subset of patients with classical Hodgkin lymphoma (cHL). However, cHLs with normal 9p24.1 copy numbers also expressed detectable PD-L1, prompting analyses of additional PD-L1 regulatory mechanisms. Herein, we utilized immunohistochemical, genomic, and functional analyses to define alternative mechanisms of PD-L1 activation in cHL and additional EBV(+) lymphoproliferative disorders. We identified an AP-1-responsive enhancer in the PD-L1 gene. In cHL Reed-Sternberg cells, which exhibit constitutive AP-1 activation, the PD-L1 enhancer binds AP-1 components and increases PD-L1 promoter activity. In addition, we defined Epstein-Barr virus (EBV) infection as an alternative mechanism for PD-L1 induction in cHLs with diploid 9p24.1. PD-L1 was also expressed by EBV-transformed lymphoblastoid cell lines as a result of latent membrane protein 1-mediated, JAK/STAT-dependent promoter and AP-1-associated enhancer activity. In addition, more than 70% of EBV(+) posttransplant lymphoproliferative disorders expressed detectable PD-L1. AP-1 signaling and EBV infection represent alternative mechanisms of PD-L1 induction and extend the spectrum of tumors in which to consider PD-1 blockade.
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                Author and article information

                Journal
                Oncotarget
                Oncotarget
                Oncotarget
                ImpactJ
                Oncotarget
                Impact Journals LLC
                1949-2553
                31 May 2016
                28 April 2016
                : 7
                : 22
                : 32925-32932
                Affiliations
                1 Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
                2 Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands
                3 The Center for Immuno-Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
                4 Department of Pathology, Ospedale di Circolo, Varese, Italy
                5 Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland, USA
                6 Department of Molecular Medicine, University of Pavia and Policlinico S. Matteo, Pavia, Italy
                7 Department of Medical Oncology, Hospital Clínico Universitario de Valencia, Valencia, Spain
                8 Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, USA
                9 Cancer Program, The Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
                Author notes
                Correspondence to: Adam J. Bass, adam_bass@ 123456dfci.harvard.edu
                Article
                9076
                10.18632/oncotarget.9076
                5078063
                27147580
                Copyright: © 2016 Derks et al.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                Categories
                Research Paper

                Oncology & Radiotherapy

                ebv-infected gastric cancers, msi gastric cancer, pd-l1, pd-1 inhibitors

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