Abstract 1053: The Influence of PD1 and TIM3 Expression on CD4+CD103+ and CD8+CD103+ Cells in Glioblastoma Progression

Abstract Glioblastoma (GB), IDH-wildtype, is the most common and aggressive high-grade primary malignant brain tumor with extremely poor outcome. Although the use of immune checkpoint inhibitors (ICIs) in GB has shown disappointing results, the identification of a small subgroup of responders underpins the role of the intratumoral immune contexture, in particular tumour-infiltrating lymphocytes (TILs), in determining disease outcome. This study aims to define the features of TIL subpopulations correlating with GB prognosis, and to establish in parallel the predictive roles of peripheral T cell subsets. A single cohort observational study, including patients undergoing GB resection and standard therapeutic and follow-up approaches in Neuro-Oncology, was conducted. Of the 45 patients, histologically confirmed WHO grade 4, 26 had MGMT promoter methylation (60.0%), 24 were male (53.3%) and the median age of young patients (≤63 years) vs elderly patients (>63 years) was 57 vs 71, respectively. Predictors of OS were KPS (≥70 vs <70: 14.7 vs 7.5 months, p=0.0007) and GTR (GTR vs non-GRT: 15 vs 9 months, p=0.004) whereas patients with methylated MGMT promoter had non-significant longer median OS compared to those with unmethylated promoter (14.5 vs 10.5 months). Patients were characterized for the expression of lineage, differentiation, memory, activation, and inhibition markers on intratumoral and peripheral CD4+ and CD8+ T cell subpopulations, and the correlation of an array of CD4+ and CD8+ T cell subsets with OS or PFS was evaluated by multiparametric flow cytometry and uni/multivariate analyses. Intratumoral immune infiltrate was positively associated with CD8+CD103+ tissue-resident memory T cells (Trm), and in particular with CD8+CD103+ Trm expressing PD1 and TIM3 rather than CD4+ Trm. Low CD8+CD103+PD1+ Trm resulted significantly associated with better OS and PFS (p=0.02 and 0.0031, respectively) and even higher significant was the correlation with better OS and PFS of low CD8+CD103+TIM3+ Trm (p=0.0002 and 0.0033, respectively) and CD8+CD103+PD1+TIM3+ Trm (p<0.0001, both). On multivariate analysis, low CD8+CD103+PD1+TIM3+ Trm and KPS ≥70 were confirmed to be the most predictive independent factors associated with longer OS (hazard ratios - HR [95%CI]: 0.14 [0.04 - 0.52] p˂0.001, 0.39 [0.16 - 0.96] p=0.04, respectively). Moreover, CD8+CD103+ Trm subpopulations resulted age-related predictors for GB survival. Consistent with this finding, in vitro PD1 and TIM3 blockade released the capability of intratumoral T cells to produce the effector cytokines IFN-γ and TNF-α, and the cytotoxic factor GrzB. Conversely, T cells expressing PD1 and TIM3 of peripheral blood did not show any prognostic significance. In conclusion, low frequency of Trm expressing PD1 or TIM3 or both markers defined TIL subsets as independent positive prognostic factors for patient survival. Citation Format: Lucia Gabriele, Giulia Romagnoli, Quintino Giorgio D'Alessandris, Imerio Capone, Andrea Tavilla, Irene Canini, Caterina Lapenta, Mariachiara Buccarelli, Martina Giordano, Valentina Tirelli, Massimo Sanchez, Alessandra Fragale, Stefano Giannetti, Rina Di Bonaventura, Liverana Lauretti, Mauro Biffoni, Lucia Ricci-Vitiani, Roberto Pallini. The Influence of PD1 and TIM3 Expression on CD4+CD103+ and CD8+CD103+ Cells in Glioblastoma Progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1053.