title: Validated programmed cell death ligand 1 immunohistochemistry assays (E1L3N and SP142) reveal similar immune cell staining patterns in melanoma when using the same sensitive detection system.
abstract: OBJECTIVE
  Tumour cell and/or immune cell programmed cell death ligand 1 (PD-L1) expression is considered as a potential biomarker for anti-PD1 and anti-PD-L1 immunotherapy. Currently, different PD-L1 assays are used. This study aims to compare the staining patterns of two PD-L1 antibody clones in melanoma metastases and correlate them with PD-L1 mRNA expression.
  
  
  RESULTS
  The immunohistochemistry assays were optimized and validated independently on a Ventana Benchmark Ultra (Ventana Medical Systems Inc., Tucson, AZ, USA) (E1L3N) and XT (SP142), using the same detection system. In total, 46 melanoma metastases were stained with both validated immunohistochemistry assays. Stained slides were digitized for qualitative and semi-quantitative evaluation; done by pathologist and semi-automated software analysis. A subset of 21 melanoma metastases was selected for quantification of the PD-L1 mRNA expression. Accuracy and precision criteria were met for both assays. PD-L1 protein and mRNA expression showed remarkably good Spearman's coefficients of 0.90 (E1L3N) and 0.87 (SP142). Despite the remarkable correlation between both PD-L1 assays in expression patterns and quantification values (ρ > 0.90), E1L3N showed significantly more tumour cell staining than SP142.
  
  
  CONCLUSIONS
  E1L3N and SP142 IHC assays were optimized and validated successfully and independently for sensitive and accurate PD-L1 detection. Concordance was best for immune cell scoring, while E1L3N tended to detect more tumour cells. Determination of the clinically relevant cut-off values for immune cell versus tumour cell detection requires further research.
authors: Department of Immunohistochemistry, HistoGeneX, Antwerp, Belgium.|Department of Medical Biochemistry, University of Antwerp, Antwerp, Belgium.
authors: Kelly A
authors: KA
authors: Schats
authors: Department of Immunohistochemistry, HistoGeneX, Antwerp, Belgium.
authors: Emily A
authors: EA
authors: Van Vré
authors: Department of Immunohistochemistry, HistoGeneX, Antwerp, Belgium.
authors: Stefanie
authors: S
authors: De Schepper
authors: Department of Immunohistochemistry, HistoGeneX, Antwerp, Belgium.
authors: Carolien
authors: C
authors: Boeckx
authors: Department of Immunohistochemistry, HistoGeneX, Antwerp, Belgium.
authors: Dorien M
authors: DM
authors: Schrijvers
authors: Department of Pathology, Universitair Ziekenhuis, Brussels, Belgium.|Department of Molecular Pathology, HistoGeneX, Antwerp, Belgium.
authors: Wim
authors: W
authors: Waelput
authors: StatUa Center for Statistics, University of Antwerp, Antwerp, Belgium.
authors: Erik
authors: E
authors: Fransen
authors: Department of Molecular Pathology, HistoGeneX, Antwerp, Belgium.
authors: Isabelle
authors: I
authors: Vanden Bempt
authors: Medical Oncology, Universitair Ziekenhuis, Brussels, Belgium.
authors: Bart
authors: B
authors: Neyns
authors: Department of Medical Biochemistry, University of Antwerp, Antwerp, Belgium.
authors: Ingrid
authors: I
authors: De Meester
authors: Department of Molecular Pathology, HistoGeneX, Antwerp, Belgium.
authors: Mark M
authors: MM
authors: Kockx
mesh_terms: D060890:B7-H1 Antigen / Q000032:analysis*; D014408:Biomarkers, Tumor / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D008545:Melanoma; D015203:Reproducibility of Results
chemical_list: D060890:B7-H1 Antigen; D014408:Biomarkers, Tumor; C423236:CD274 protein, human
keywords: E1L3N; Nanostring; PD-L1; SP142; immunohistochemistry