Programmed death ligand 1 expression and tumor-infiltrating lymphocytes in glioblastoma

Background Immune checkpoint inhibitors targeting programmed cell death 1 (PD1) or its ligand (PD-L1) showed activity in several cancer types. Methods We performed immunohistochemistry for CD3, CD8, CD20, HLA-DR, phosphatase and tensin homolog (PTEN), PD-1, and PD-L1 and pyrosequencing for assessment of the O6-methylguanine-methyltransferase (MGMT) promoter methylation status in 135 glioblastoma specimens (117 initial resection, 18 first local recurrence). PD-L1 gene expression was analyzed in 446 cases from The Cancer Genome Atlas. Results Diffuse/fibrillary PD-L1 expression of variable extent, with or without interspersed epithelioid tumor cells with membranous PD-L1 expression, was observed in 103 of 117 (88.0%) newly diagnosed and 13 of 18 (72.2%) recurrent glioblastoma specimens. Sparse-to-moderate density of tumor-infiltrating lymphocytes (TILs) was found in 85 of 117 (72.6%) specimens (CD3+ 78/117, 66.7%; CD8+ 52/117, 44.4%; CD20+ 27/117, 23.1%; PD1+ 34/117, 29.1%). PD1+ TIL density correlated positively with CD3+ (P < .001), CD8+ (P < .001), CD20+ TIL density (P < .001), and PTEN expression (P = .035). Enrichment of specimens with low PD-L1 gene expression levels was observed in the proneural and G-CIMP glioblastoma subtypes and in specimens with high PD-L1 gene expression in the mesenchymal subtype (P = 5.966e-10). No significant differences in PD-L1 expression or TIL density between initial and recurrent glioblastoma specimens or correlation of PD-L1 expression or TIL density with patient age or outcome were evident. Conclusion TILs and PD-L1 expression are detectable in the majority of glioblastoma samples but are not related to outcome. Because the target is present, a clinical study with specific immune checkpoint inhibitors seems to be warranted in glioblastom

Correlation of immune phenotype with IDH mutation in diffuse glioma

BACKGROUND: Tumor infiltrating lymphocytes (TILs) and programmed death ligand 1 (PD-L1) are targets of immune checkpoint inhibitors. METHODS: Forty-three World Health Organization (WHO) grade II/III gliomas (39 IDH-mutant [mut], 4 IDH-wildtype [wt]) and 14 IDH-mut glioblastomas (GBM) were analyzed for TIL (CD3+; PD1+) infiltration and PD-L1 expression. Results were compared with the data of a previously published series of 117 IDH-wt glioblastomas. PD-L1 gene expression levels were evaluated in 677 diffuse gliomas grades II-IV from The Cancer Genome Atlas (TCGA) database. RESULTS: TIL and PD-L1 expression were observed in approximately half of WHO grade II/III gliomas. IDH-wt status was associated with significantly higher TIL infiltration and PD-L1 expression among all (grades II-IV) cases (n = 174, P < 0.001) and within the cohort of glioblastomas (n = 131, P < 0.001). In low-grade glioma (LGG) and glioblastoma cohorts of TCGA, significantly higher PD-L1 gene expression levels were evident in IDH-wt compared with IDH-mut samples (LGG: N = 516; P = 1.933e-11, GBM: N = 161; P < 0.009). Lower PD-L1 gene expression was associated with increased promoter methylation (Spearman correlation coefficient -0.36; P < 0.01) in the LGG cohort of TCGA. IDH-mut gliomas had higher PD-L1 gene promoter methylation levels than IDH-wt gliomas (P < 0.01). CONCLUSIONS: The immunological tumor microenvironment of diffuse gliomas differs in association with IDH mutation status. IDH-wt gliomas display a more prominent TIL infiltration and higher PD-L1 expression than IDH-mut cases. Mechanistically this may be at least in part due to differential PD-L1 gene promoter methylation levels. Our findings may be relevant for immune modulatory treatment strategies in glioma patients.This study was funded by the research budget of the Medical University of Vienna and a grant by the “Hochschuljubuläumsstiftung” with the project title “Das Immunsystem im Kampf gegen Krebs” and the Swiss National Science Foundation 31003A_163297

Invasion patterns in brain metastases of solid cancers

Background Brain metastases are generally considered to be well demarcated from the surrounding brain parenchyma, although infiltrative growth patterns have been observed. We systemically investigated infiltration patterns and expression of adhesion molecules in a large and well-defined series of autopsy cases of brain metastases. Methods Ninety-seven autopsy specimens from 57 brain metastasis patients (primary tumor: 27 lung cancer, 6 breast cancer, 8 melanoma, 2 colorectal cancer, 1 kidney cancer, and 13 other) were evaluated for patterns of invasion into surrounding brain parenchyma. Expression of integrins αv; cytoplasmic β3, αvβ3, αvβ5, αvβ6, and αvβ8; and of E and N cadherin were evaluated using immunohistochemistry. Results Three main invasion patterns were seen: well-demarcated growth (29/57, 51%), vascular co-option (10/57, 18%), and diffuse infiltration (18/57, 32%). There was no statistically significant association of invasion pattern with primary tumor type, although vascular co-option was most common in melanoma brain metastases (4/10). Invasion patterns of different brain metastases of the same patient were highly concordant (P < .001, chi-square test). Distance of infiltration from the main tumor mass ranged from 12.5 µm to 450 µm (median 56.2 µm) and was not significantly different between the vascular co-option and the diffuse infiltration groups. Levels of αvβ6 were significantly higher in the well-demarcated group than in the vascular co-option and the diffuse infiltration groups (P = .033, Kruskal-Wallis test). Expression of αvβ5 in tumor cells was higher in brain metastasis lesions previously treated with stereotactic radiosurgery (P = .034, chi-square test). Conclusions Distinct invasion patterns of brain metastases into the brain parenchyma are not specific for primary tumor types, seem to be influenced by expression of αv integrin complexes, and may help to guide clinical decision-making