Comprehensive immunohistochemical analysis of PD-L1 shows scarce expression in castration-resistant prostate cancer

Christian D Fankhauser, Peter J Schüffler, Silke Gillessen, Aurelius Omlin, Niels J Rupp, Jan H Rueschoff, Thomas Hermanns, Cedric Poyet, Tullio Sulser, Holger Moch, Peter J Wild

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Abstract

Background: We aimed to analyze the frequency and distribution of PD-L1 expression in specimens from prostate cancer (PC) patients using two different anti-PD-L1 antibodies (E1L3N, SP263).

Materials and Methods: PD-L1 immunohistochemistry was performed in a tissue microarray consisting of 82 castration-resistant prostate cancer (CRPC) specimens, 70 benign prostate hyperplasia (BPH) specimens, 96 localized PC cases, and 3 PC cell lines, using two different antibodies (clones E1L3N, and SP263). Staining images for CD4, CD8, PD-L1, and PanCK of a single PD-L1 positive case were compared, using a newly developed dot-wise correlation method for digital images to objectively test for co-expression.

Results: Depending on the antibody used, in tumor cells (TC) only five (E1L3N: 6%) and three (SP263: 3.7%) samples were positive. In infiltrating immune cells (IC) 12 (SP263: 14.6%) and 8 (E1L3N: 9.9%) specimens showed PD-L1 expression. Two PC cell lines (PC3, LnCaP) also displayed membranous immunoreactivity. All localized PCs or BPH samples tested were negative. Dot-wise digital correlation of expression patterns revealed a moderate positive correlation between PD-L1 and PanCK expression, whereas both PanCK and PD-L1 showed a weak negative Pearson correlation coefficient between CD4 and CD8.

Conclusions: PD-L1 was not expressed in localized PC or BPH, and was only found in a minority of CRPC tumors and infiltrating immune cells. Protein expression maps and systematic dot-wise comparison could be a useful objective way to describe the relationship between immuno- and tumor-related proteins in the future, without the need to develop multiplex staining methods.

Original languageEnglish
Pages (from-to)10284-10293
Number of pages10
JournalOncotarget
Volume9
Issue number12
DOIs
Publication statusPublished - 4 Dec 2017

Research Beacons, Institutes and Platforms

  • Manchester Cancer Research Centre

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