OS12.7.A INTEGRATED DIGITAL PATHOLOGY AND TRANSCRIPTOMIC ANALYSIS OF ADULT GLIOMAS WITH HIGH LYMPHOCYTE INFILTRATION IDENTIFIES CELLULAR AND SPATIAL DETERMINANTS OF IMMUNE INFILTRATION WITH PROGNOSTIC VALUE
Authors: Salhi L , Lerond J , Nadaradjane A A , Drouiche L , Otero Pizarro M M , Hanna Doumit Sakr L , Labreche K , Kacimi S E O , Bellamy C , Picca A , Stimmer L , Brocic J , Letourneur Q , Barka B , Carpentier C , Marie Y , Madry H , Bhalshankar J , Nicolle R , Malaizé H , Mathon B , Mokhtari K , Idbaih A , Hoang-Xuan K , Sanson M , Alentorn A , Duval A , Le Rouzic P , Dieu-Nosjean M , Bloch I , Touat M , Bielle F 
Published: October 2024

Abstract

BACKGROUND
Adult glioma patients rarely benefit from immunotherapy. This lack of efficacy has been related to gliomas immune “cold” microenvironment, which is commonly observed in these tumors and reduces lymphocyte-mediated antitumor responses. Here, we investigated the immune microenvironment of rare adult gliomas with high lymphocytic infiltration in order to evaluate the biology of this unusual immune response, its prognostic value and its potential role as predictive biomarker for immunotherapy strategies.

MATERIAL AND METHODS
Two retrospective cohorts of adult gliomas were analyzed: a supervised cohort of 206 samples enriched for tumors with high lymphocytic infiltration (including glioblastoma IDH wildtype [GBM], gemistocytic variant of astrocytoma IDH-mutant, ganglioglioma [GGG] and pleomorphic xanthoastrocytoma [PXA], and hypermutated mismatch repair deficient gliomas [MMRd]), and a consecutive cohort of 112 samples as control of the usual epidemiology. Immune microenvironment was characterized through (i) an analysis of spatial patterns and semi-automated quantification of T lymphocytes on CD3 immunolabeling and (ii) deconvolution of immune cells content from bulk RNA sequencing of FFPE tumor tissue. Cellular and spatial patterns of immune infiltration were correlated with demographic, histomolecular and outcome features. We investigated the underlying biology through multiplex immunolabeling and single-cell RNAseq of FACS-sorted intratumoral immune cells. Results: We identified three main spatial patterns (perivascular, peritumoral, diffuse intratumoral) of T cells infiltration in addition to the most usual aspect of scarce tumor-infiltrating lymphocytes. T cell proportion exhibited a wide range of distribution and was significantly associated with tumor type and IDH-status, with GBM, PXA and GGG exhibiting the highest proportions. Using transcriptomic signatures of immune cells and deconvolution of bulk RNAseq data, we observed recurrent patterns of associated immune cell types across diverse tumor types. We analyzed the correlations of these spatial and cellular immune patterns with tumor types and genetic alterations. Multiplex immunolabeling and single cell RNAseq revealed distinct T cells subpopulations, as well as potential functional states and cell-cell communication pathways driving these states. T cell infiltration had a significant prognostic impact among GBM patients.

CONCLUSION
Adult gliomas with high lymphocytic content stands for a population of interest to better understand immune responses in the brain parenchyma and develop novel immunotherapy clinical trials. Our results suggest that therapeutic evaluation requires an adjustment due to the prognostic impact of immune microenvironment.