title: The Immune Microenvironment, Genome-wide Copy Number Aberrations, and Survival in Mesothelioma.
abstract: Results of recent clinical studies of immune checkpoint inhibitors in malignant pleural mesothelioma (MPM) have dampened initial enthusiasm. However, the immune environment and targets of these treatments such as programmed cell death protein 1 and its ligand programmed death ligand 1 (PD-L1) have not been well characterized in MPM. Using a large cohort of patients, we investigated PD-L1 expression, immune infiltrates, and genome-wide copy number status and correlated them to clinicopathological features.
  
  
  
  Tissue microarrays were constructed and stained with PD-L1(clone E1L3N [Cell Signaling Technology, Danvers, MA]), cluster of differentiation 4, cluster of differentiation 8, and forkhead box P3 antibodies. PD-L1 positivity was defined as at least 5% membranous staining regardless of intensity, and high PD-L1 positivity was defined as at least 50%. Genomic DNA from a representative subset of 113 patients was used for genome-wide copy number analysis. The percent genome alteration was computed as a proxy for genomic instability, and statistical analyses were used to relate copy number aberrations to other variables.
  
  
  
  Among 329 patients evaluated, PD-L1 positivity was detected in 130 of 311 (41.7%), but high PD-L1 positivity was seen in only 30 of 311 (9.6%). PD-L1 positivity correlated with nonepithelioid histological subtype and increased infiltration with cluster of differentiation 4-positive, cluster of differentiation 8-positive, and forkhead box P3-positive lymphocytes. High PD-L1-positive expression correlated with worse prognosis (hazard ratio = 2.37, 95% confidence interval: 1.57-3.56, p < 0.001) in univariate analysis but not in multivariate analysis. Higher percent genome alteration was associated with epithelioid histological subtype and poorer survival (hazard ratio = 1.59, 95% confidence interval: 1.01-2.5, p = 0.04) but not PD-L1 expression.
  
  
  
  PD-L1 expression was associated with nonepithelioid MPM, poor clinical outcome, and increased immunological infiltrates. Increased genomic instability did not correlate with PD-L1 expression but was associated with poorer survival.
authors.affiliation: Department of Medicine, University of Melbourne, Parkville, Victoria, Australia; Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia.
authors.forename: Bibhusal
authors.initials: B
authors.lastname: Thapa
authors.affiliation: Informatics and Biocomputing Program, Ontario Institute for Cancer Research, Toronto, Canada.
authors.forename: Adriana
authors.initials: A
authors.lastname: Salcedo
authors.affiliation: Informatics and Biocomputing Program, Ontario Institute for Cancer Research, Toronto, Canada.
authors.forename: Xihui
authors.initials: X
authors.lastname: Lin
authors.affiliation: Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia.
authors.forename: Marzena
authors.initials: M
authors.lastname: Walkiewicz
authors.affiliation: Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia; Department of Pathology, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: Carmel
authors.initials: C
authors.lastname: Murone
authors.affiliation: Department of Medical Oncology, Austin Health, Olivia-Newton John Cancer and Wellness Centre, Heidelberg, Victoria, Australia.
authors.forename: Malaka
authors.initials: M
authors.lastname: Ameratunga
authors.affiliation: Department of Pathology, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: Khashyar
authors.initials: K
authors.lastname: Asadi
authors.affiliation: Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia.
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Deb
authors.affiliation: Department of Thoracic Surgery, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: Stephen Arthur
authors.initials: SA
authors.lastname: Barnett
authors.affiliation: Department of Thoracic Surgery, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Knight
authors.affiliation: Department of Medical Oncology, Austin Health, Olivia-Newton John Cancer and Wellness Centre, Heidelberg, Victoria, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.affiliation: Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia.
authors.forename: D Neil
authors.initials: DN
authors.lastname: Watkins
authors.affiliation: Informatics and Biocomputing Program, Ontario Institute for Cancer Research, Toronto, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Canada; Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Boutros
authors.affiliation: Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia; Department of Medical Oncology, Austin Health, Olivia-Newton John Cancer and Wellness Centre, Heidelberg, Victoria, Australia; School of Cancer Medicine, La Trobe University, Bundoora, Victoria, Australia. Electronic address: tom.john@onjcri.org.au.
authors.forename: Thomas
authors.initials: T
authors.lastname: John
mesh_terms: D000368:Aged; D060890:B7-H1 Antigen / Q000276:immunology* / Q000378:metabolism; D015704:CD4 Antigens / Q000378:metabolism; D016827:CD8 Antigens / Q000378:metabolism; D056915:DNA Copy Number Variations; D005260:Female; D051858:Forkhead Transcription Factors / Q000378:metabolism; D055106:Genome-Wide Association Study; D042822:Genomic Instability; D006801:Humans; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology* / Q000378:metabolism; D008297:Male; D008654:Mesothelioma / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D010997:Pleural Neoplasms / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D015996:Survival Rate; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D046888:Tissue Array Analysis; D059016:Tumor Microenvironment / Q000276:immunology*
chemical_list: D060890:B7-H1 Antigen; C423236:CD274 protein, human; D015704:CD4 Antigens; D016827:CD8 Antigens; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors
keywords: Copy number aberrations; Immunohistochemistry; Mesothelioma; PD-L1; Tumor-infiltrating lymphocytes