Immunophenotyping of Newly Diagnosed and Recurrent Glioblastoma Defines Distinct Immune Exhaustion Profiles in Peripheral and Tumor-infiltrating Lymphocytes

Purpose: Immunotherapeutic treatment strategies for glioblastoma (GBM) are under investigation in clinical trials. However, our understanding of the immune phenotype of GBM-infiltratingT cells (tumor-infiltrating lymphocytes; TILs) and changes during disease progression is limited. Deeper insight is urgently needed to therapeutically overcome tumor-induced immune exhaustion. Experimental Design: We used flow cytometry and cytokine assays to profile TILs and peripheral blood lymphocytes (PBLs) from patients with GBM, comparing newly diagnosed or recurrent GEM to long-term survivors (US) and healthy donors. TCR sequencing was performed on paired samples of newly diagnosed and recurrent GBM. Results: We identified a dear immune signature of exhaustion and clonal restriction in the TILs of patients with GEM. Exhaustion of CD8+ TILs was defined by an increased prevalence of PD-1(+), CD39(+), Tim-3(+), CD45RO(+), HLA-DR+ marker expression, and exhibition of an effector-/transitional memory differentiation phenotype, whereas KLRG1 and CD57 were underrepresented. Immune signatures were similar in primary and recurrent tumors; however, restricted TCR repertoire donality and a more activated memory phenotype were observed in TILs from recurrent tumors. Moreover, a reduced cytokine response to PHA stimulation in the blood compartment indicates a dysfunctional peripheral T-cell response in patients with GBM. LTS displayed a distinct profile, with abundant naive and less exhausted CD8(+) T cells. Conclusions: TILs and PBLs exhibit contrasting immune profiles, with a distinct exhaustion signature present in TILs. While the exhaustion profiles of primary and recurrent GEM are comparable, TCR sequencing demonstrated a contracted repertoire in recurrent GBM, concomitant with an increased frequency of activated memory T cells in recurrent tumors. (C) 2018 AACR.