Patterns of PD-L1 expression and CD8 T cell infiltration in gastric adenocarcinomas and associated immune stroma

Elizabeth D. Thompson, Marianna Zahurak, Adrian Murphy, Toby Cornish, Nathan Cuka, Eihab Abdelfatah, Stephen Yang, Mark Duncan, Nita Ahuja, Janis M. Taube, Robert A. Anders, Ronan J. Kelly

Research output: Contribution to journalArticlepeer-review

Abstract

Objective Recent data supports a significant role for immune checkpoint inhibitors in the treatment of solid tumours. Here, we evaluate gastric and gastrooesophageal junction (G/GEJ) adenocarcinomas for their expression of programmed death-ligand 1 (PD-L1), infiltration by CD8+ T cells and the relationship of both factors to patient survival. Design Thirty-four resections of primary invasive G/GEJ were stained by immunohistochemistry for PD-L1 and CD8 and by DNA in situ hybridisation for Epstein-Barr virus (EBV). CD8+ T cell densities both within tumours and at the tumour-stromal interface were analysed using whole slide digital imaging. Patient survival was evaluated according to PD-L1 status and CD8 density. Results 12% of resections showed tumour cell membranous PD-L1 expression and 44% showed expression within the immune stroma. Two cases (6%) were EBV positive, with one showing membranous PD-L1 positivity. Increasing CD8+ densities both within tumours and immune stroma was associated with increasing percentage of tumour (p=0.027) and stromal (p=0.005) PD-L1 expression. Both tumour and immune stromal PD-L1 expression and high intratumoral or stromal CD8+ T cell density (>500/mm2) were associated with worse progression-free survival (PFS) and overall survival (OS). Conclusions PD-L1 is expressed on both tumour cells and in the immune stroma across all stages and histologies of G/GEJ. Surprisingly, we demonstrate that increasing CD8 infiltration is correlated with impaired PFS and OS. Patients with higher CD8+ T cell densities also have higher PD-L1 expression, indicating an adaptive immune resistance mechanism may be occurring. Further characterisation of the G/GEJ immune microenvironment may highlight targets for immunebased therapy.

Original languageEnglish (US)
Pages (from-to)794-801
Number of pages8
JournalGut
Volume66
Issue number5
DOIs
StatePublished - Jan 22 2016

ASJC Scopus subject areas

  • Gastroenterology

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