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Validated programmed cell death ligand 1 immunohistochemistry assays (E1L3N and SP 142) reveal similar immune cell staining patterns in melanoma when using the same sensitive detection system
Author(s) -
Schats Kelly A,
Van Vré Emily A,
De Schepper Stefanie,
Boeckx Carolien,
Schrijvers Dorien M,
Waelput Wim,
Fransen Erik,
Vanden Bempt Isabelle,
Neyns Bart,
De Meester Ingrid,
Kockx Mark M
Publication year - 2017
Publication title -
histopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.626
H-Index - 124
eISSN - 1365-2559
pISSN - 0309-0167
DOI - 10.1111/his.13056
Subject(s) - immunohistochemistry , staining , melanoma , concordance , pathology , immune system , biology , antibody , biopsy , companion diagnostic , pd l1 , cell , microbiology and biotechnology , immunotherapy , medicine , cancer research , cancer , immunology , bioinformatics , genetics
Aims Tumour cell and/or immune cell programmed cell death ligand 1 ( PD ‐L1) expression is considered as a potential biomarker for anti‐ PD 1 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. Methods and results The immunohistochemistry assays were optimized and validated independently on a Ventana Benchmark Ultra (Ventana Medical Systems Inc., Tucson, AZ , USA ) (E1L3N) and XT ( SP 142), 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 ( SP 142). 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 SP 142. Conclusions E1L3N and SP 142 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.