Extracellular vesicles, including exosomes, are released by all cells, including those of the nervous system. Capable of delivering lipid, protein and nucleic acids to both nearby and distal cells, exosomes have been hypothesized to play a role in progression of many diseases of the nervous system. To date, most analyses on the role of these vesicles in the healthy and diseased state have relied on studying vesicles from in vitro sources, such as conditioned cell culture media, or body fluids. Here we have taken a critical approach to the enrichment and characterization of exosomes from human frontal cortex. This method maintains the integrity of the vesicles and their cargo, and comprehensive proteomic and genomic characterization confirms the legitimacy of the resulting extracellular vesicles as endosome-derived exosomes. This method will enable neuroscientists to acquire more detailed information about exosomes in the brain and explore the role(s) this form of intercellular communication and unique source of lipid, protein and RNA has in healthy brain function and pathogenic conditions. Furthermore, this method may have important utility in the isolation of exosomes from other tissues.

BackgroundLymphocyte activating 3 (LAG3, LAG-3, CD223) is a promising target for immune checkpoint inhibition in clear cell renal cell carcinoma (KIRC). The aim of this study was to investigate the epigenetic regulation ofLAG3in KIRC by methylation.MethodsWe correlated quantitativeLAG3methylation levels with transcriptional activity, immune cell infiltration, and overall survival in a cohort of n=533 patients with KIRC and n=160 normal adjacent tissue (NAT) samples obtained from The Cancer Genome Atlas (TCGA). Furthermore, we analyzedLAG3methylation in peripheral blood mononuclear cells (PBMCs) and KIRC cell lines. We validated correlations between LAG3 expression, immune cell infiltrates, survival, and methylation in an independent KIRC cohort (University Hospital Bonn (UHB) cohort, n=118) by means of immunohistochemistry and quantitative methylation-specific PCR.ResultsWe found differential methylation profiles among PBMCs, NAT, KIRC cell lines, and KIRC tumor tissue. Methylation strongly correlated with LAG3 mRNA expression in KIRCs (TCGA cohort) and KIRC cell lines. In the UHB cohort, methylation correlated with LAG3-positive immune cells and tumor-intrinsic LAG3 protein expression. Furthermore,LAG3methylation strongly correlated with signatures of distinct immune cell infiltrates, an interferon-y signature (TCGA cohort), and immunohistochemically quantified CD45+, CD8+, and CD4+immune cell infiltrates (UHB cohort). LAG3 mRNA expression (TCGA cohort), methylation (both cohorts), and tumor cell-intrinsic protein expression (UHB cohort) was significantly associated with overall survival.ConclusionOur data suggest an epigenetic regulation of LAG3 expression in tumor and immune cells via DNA methylation. LAG3 expression and methylation is associated with a subset of KIRCs showing a distinct clinical course and immunogenicity. Our study provides rationale for further testingLAG3DNA methylation as a predictive biomarker for response to LAG3 immune checkpoint inhibitors.

Background: Immunotherapy, including checkpoint inhibition, has remarkably improved prognosis in advanced melanoma. Despite this success, acquired resistance is still a major challenge. The T cell costimulatory receptor TNFRSF9 (also known as 4-1BB and CD137) is a promising new target for immunotherapy and two agonistic antibodies are currently tested in clinical trials. However, little is known about epigenetic regulation of the encoding gene. In this study we investigate a possible correlation of TNFRSF9 DNA methylation with gene expression, clinicopathological parameters, molecular and immune correlates, and response to anti-PD-1 immunotherapy to assess the validity of TNFRSF9 methylation to serve as a biomarker. Methods: We performed a correlation analyses of methylation at twelve CpG sites within TNFRSF9 with regard to transcriptional activity, immune cell infiltration, mutation status, and survival in a cohort of N = 470 melanoma patients obtained from The Cancer Genome Atlas. Furthermore, we used quantitative methylation-specific PCR to confirm correlations in a cohort of N = 115 melanoma patients' samples (UHB validation cohort). Finally, we tested the ability of TNFRSF9 methylation and expression to predict progression-free survival (PFS) and response to anti-PD-1 immunotherapy in a cohort comprised of N = 121 patients (mRNA transcription), (mRNA ICB cohort) and a case-control study including N = 48 patients (DNA methylation, UHB ICB cohort). Findings: We found a significant inverse correlation between TNFRSF9 DNA methylation and mRNA expression levels at six of twelve analyzed CpG sites (P 0.005), predominately located in the promoter flank