Expression of PD-L1 and immune cells in gastrointestinal stromal tumours

Abstract

Introduction. Tumour microenvironment and the expression of check-point molecules on tumour cells was proven to have prognostic and therapeutic implications in various types of cancer. Evaluation of immune infiltrate and Programmed Death-1 (PD-L1) expression in gastrointestinal stromal tumours (GISTs) could bring valuable information for development of targeted immune therapy for a subset of cases. The objective of this study was to determine the PD-L1 expression and to analyse the intratumoural inflammatory infiltrate in different categories of GISTs. Material and methods. Twenty four cases of immunohistochemically confirmed GISTs were microscopically reviewed and tested for PD-L1, CD3 and CD20. Their expression was quantified and statistical analysis was performed to search for differences between subgroups. Results. The expression of PD-L1 on tumour cells was identified in fourteen cases, with variable intensity and extent, ten cases being negative. The immune infiltrate was invariably present, lymphocytic predominant, with intertumoural and intratumoural quantitative differences, from sparse to abundant and with focal aggregation around blood vessels, fibrous septa, in the periphery of the tumour and under ulcerated areas. T cells were the dominant lymphocytic subtype. Causality connections could not be determined between PD-L1 expression, the pattern of inflammation and other clinical and pathological variables, limitation determined in part by the reduced extent of the study. Conclusions. GISTs express PD-L1 in a significant percentage of cases and have a great variability in the number and distribution of intratumoural immune cells, aspects that can be further exploited for therapeutic purposes.

Keywords

• gastrointestinal stromal tumour
• check-point molecules
• pd-l1
• immune cells
• immunotherapy