T cell infiltration into Ewing sarcomas is associated with local expression of immune-inhibitory HLA-G

// Christian Spurny 1 , Sareetha Kailayangiri 1 , Bianca Altvater 1 , Silke Jamitzky 1 , Wolfgang Hartmann 2 , Eva Wardelmann 2 , Andreas Ranft 1, 3 , Uta Dirksen 1, 3 , Susanne Amler 4 , Jendrik Hardes 5, 4 , Maike Fluegge 1 , Jutta Meltzer 1 , Nicole Farwick 1 , Lea Greune 1 and Claudia Rossig 1, 6 1 Department of Pediatric Hematology and Oncology, University Children´s Hospital Muenster, Muenster, Germany 2 Gerhard Domagk Institute of Pathology, University of Muenster, Muenster, Germany 3 University Hospital Essen, Pediatrics III, West German Cancer Centre, Essen, Germany 4 Institute of Biostatistics and Clinical Research, University of Muenster, Muenster, Germany 5 Department of Orthopedic Surgery, University Hospital Muenster, Muenster, Germany 6 Cells-in-Motion Cluster of Excellence (EXC 1003 – CiM), University of Muenster, Germany Correspondence to: Claudia Rossig, email: rossig@uni-muenster.de Keywords: Ewing sarcoma; HLA-G; T cells; cellular immunotherapy; immune checkpoints Received: September 08, 2017 Accepted: October 27, 2017 Published: December 22, 2017 ABSTRACT Ewing sarcoma (EwS) is an aggressive mesenchymal cancer of bones or soft tissues. The mechanisms by which this cancer interacts with the host immune system to induce tolerance are not well understood. We hypothesized that the non-classical, immune-inhibitory HLA-molecule HLA-G contributes to immune escape of EwS. While HLA-G pos suppressor T cells were not increased in the peripheral blood of EwS patients, HLA-G was locally expressed on the tumor cells and/or on infiltrating lymphocytes in 16 of 47 pretherapeutic tumor biopsies and in 4 of 12 relapse tumors. HLA-G expression was not associated with risk-related patient variables or response to standard chemotherapy, but with significantly increased numbers of tumor-infiltrating CD3+ T cells compared to HLA-G neg EwS biopsies. In a mouse model, EwS xenografts after adoptive therapy with tumor antigen-specific CAR T cells strongly expressed HLA-G whereas untreated control tumors were HLA-G neg . IFN-γ stimulation of EwS cell lines in vitro induced expression of HLA-G protein. We conclude that EwS cells respond to tumor-infiltrating T cells by upregulation of HLA-G, a candidate mediator of local immune escape. Strategies that modulate HLA-G expression in the tumor microenvironment may enhance the efficacy of cellular immunotherapeutics in this cancer.