title: Increased PD-L1 and T-cell infiltration in the presence of HLA class I expression in metastatic high-grade osteosarcoma: a rationale for T-cell-based immunotherapy.
abstract: Immunotherapy may be an excellent choice for treating osteosarcoma given its exceptionally high genomic instability, potentially generating neoantigens. In this study, we aim to investigate the HLA class I expression, PD-L1 and tumour-infiltrating lymphocytes in primary osteosarcomas and relapses/metastases, as well as their changes during disease progression.
  
  
  
  Tumour samples from multiple stages of the disease (pretreatment biopsies, surgical resections of primary osteosarcomas, relapses and metastases) were collected and stained for HLA-A (HCA2), HLA-B/C (HC10), β2-microglobulin and PD-L1 using immunohistochemistry on whole sections. Density and type of T-cell infiltrate were characterised by a triple immunofluorescent staining CD3-CD8-FOXP3.
  
  
  
  Overall, 85 formalin-fixed, paraffin-embedded blocks from 25 osteosarcoma patients were included. HLA class I expression was detected in 94% of osteosarcomas (strongly positive in 56%, heterogeneous in 38%) and negative or weakly positive in 6%, without differences between the stages of the disease. HLA-A expression was more frequently negative than HLA-B/C. Tumour-infiltrating lymphocytes were highly heterogeneous and mainly observed in tumour areas with expression of HLA class I. Density of T cells was significantly higher in metastases than in primary tumours and local relapses (p = 0.0003). Positive PD-L1 expression was found in 13% of primary tumours, 25% of relapses and 48% of metastases and correlated with a high T-cell infiltrate (p = 0.002).
  
  
  
  An increased number of tumour-infiltrating T cells and PD-L1 expression in metastases compared with primary tumours, suggesting accessibility for T cells, could imply that osteosarcoma patients with metastatic disease may benefit from T-cell-based immunotherapy.
authors.affiliation: Department of Pathology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Yayan T
authors.initials: YT
authors.lastname: Sundara
authors.affiliation: Department of Pathology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.|Department of Rheumatology, Hôpital Pellegrin, Centre Hospitalier Universitaire de Bordeaux, Bordeaux, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Kostine
authors.affiliation: Department of Pathology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Arjen H G
authors.initials: AH
authors.lastname: Cleven
authors.affiliation: Department of Pathology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Judith V M G
authors.initials: JV
authors.lastname: Bovée
authors.affiliation: Department of Pediatrics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Marco W
authors.initials: MW
authors.lastname: Schilham
authors.affiliation: Department of Pathology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands. a.m.cleton-jansen@lumc.nl.
authors.forename: Anne-Marie
authors.identifier: 0000-0002-9048-4867
authors.initials: AM
authors.lastname: Cleton-Jansen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D060890:B7-H1 Antigen / Q000096:biosynthesis* / Q000276:immunology; D014408:Biomarkers, Tumor / Q000276:immunology; D001859:Bone Neoplasms / Q000276:immunology / Q000628:therapy*; D002648:Child; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D012516:Osteosarcoma / Q000276:immunology / Q000628:therapy*; D011379:Prognosis; D055815:Young Adult
chemical_list: D060890:B7-H1 Antigen; D014408:Biomarkers, Tumor; C423236:CD274 protein, human; D015395:Histocompatibility Antigens Class I
keywords: HLA class I; Immunotherapy; Osteosarcoma; PD-L1; Tumour-infiltrating lymphocytes