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

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

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
StatePublished - 2018
Externally publishedYes

Keywords

  • Immune response
  • Immunotherapy
  • PD-L1
  • Prostate cancer

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