Lymphocyte-activation gene 3 (LAG-3) expression in the inflammatory microenvironment of glioma.

Abstract

2553 Background: The blockade of lymphocyte-activation gene 3 (LAG-3), an inhibitory receptor on tumor-infiltrating lymphocytes, is currently under investigation in many extracranial tumor entities. Methods: 54 patients with diffuse glioma were included: 35 patients with glioblastoma (GBM, median age at diagnosis: 61 years) as well as 14 with WHO grade II and 5 with WHO grade III glioma (lower-grade glioma, LGG, median age at diagnosis: 45 years). Isocitrate dehydrogenase 1/2 mutations (IDH-mt) were present in 17/54 patients and 37/54 patients had IDH wildtype (IDH-wt) tumors. LAG-3 expression on tumor-infiltrating lymphocytes (TILs) was analyzed by immunohistochemistry (monoclonal anti-LAG-3 antibody, clone 17B4, LSBio Inc.). Results: LAG-3+ TILs could be observed in 5/54 (9.3%) samples, while CD3+ TILs were present in 32/54 (59.3%) and CD8+ TILs in 24/54 (44.4%) samples. Only IDH-wt glioma presented with LAG-3+ TILs (p = 0.168). Samples with LAG-3+ TILs presented with a numerical trend towards higher presence of CD3+ (5/27 CD3+ vs. 0/22 CD3−, p = 0.072) and CD8+ TILs (4/24 CD8+ vs. 1/30 CD8−, p = 0.159). 4/7 (57.1%) samples presenting with PD-1+ TILs also presented with LAG-3+ TILs (p = 0.001). Furthermore, glioma samples with LAG3+ TILs presented with higher expression of PD-L1 (median: 1% vs. 0%; p = 0.166). There was no difference in overall survival (OS) according to LAG-3+ TIL infiltration (median OS in LAG-3+: 21.7 months vs. LAG-3−: 41.4 months, p > 0.05). Conclusions: LAG-3+ TILs are rarely observed in IDH-wt and absent in IDH-mt glioma. Gliomas with an active inflammatory microenvironment present more frequently with LAG3+ TILs. The diverse composition of the inflammatory microenvironment and particular inflammatory subgroups should be considered in future clinical trials on immune-modulating therapies in glioma.