BackgroundIn recent years, PD-1/PD-L1 immune checkpoint inhibitors have improved cancer therapy in many tumor types, but no benefit of immune checkpoint therapy has been found in glioblastoma multiforme (GBM). Based on the results of our earlier work, which showed a reduction of PD-L1 expression in patients treated with temozolomide (TMZ), we aimed to investigate the link between TMZ therapy and the immune control point target PD-L1.MethodsRNA-sequencing data from de-novo and recurrent glioblastoma were analyzed by AutoPipe algorithm. Results were confirmed either in a cell model by two primary and one established GBM cell line and specimens of de-novo and recurrent GBM. PD-L1 and pathway activation of the JAK/STAT pathway was analyzed by quantitative real-time PCR and western blot.ResultsWe found a significant downregulation of the JAK/STAT pathway and immune response in recurrent tumors. The cell model showed an upregulation of PD-L1 after IFNγ treatment, while additional TMZ treatment lead to a reduction of PD-L1 expression and JAK/STAT pathway activation. These findings were confirmed in specimens of de-novo and recurrent glioblastoma.ConclusionsOur results suggest that TMZ therapy leads to a down-regulation of PD-L1 in primary GBM cells. These results support the clinical findings where PD-L1 is significantly reduced in recurrent GBMs. If the target is diminished, it may also lead to impaired efficacy of PD-1/PD-L1 inhibitors such as nivolumab.

Long-term epilepsy-associated tumors (LEATs) represent mostly benign brain tumors associated with drug-resistant epilepsy. The aim of the study was to investigate the specific transcriptional signatures of those tumors and characterize their underlying oncogenic drivers. A cluster analysis of 65 transcriptome profiles from three independent datasets resulted in four distinct transcriptional subgroups. The first subgroup revealed transcriptional activation of STAT3 and TGF-signaling pathways and contained predominantly dysembryoplastic neuroepithelial tumors (DNTs). The second subgroup was characterized by alterations in the MAPK-pathway and upstream cascades including FGFR and EGFR-mediated signaling. This tumor cluster exclusively contained neoplasms with somatic BRAF V600E mutations and abundance of gangliogliomas (GGs) with a significantly higher recurrence rate (42%). This finding was validated by examining recurrent tumors from the local database exhibiting BRAF V600E in 90% of the cases. The third cluster included younger patients with neuropathologically diagnosed GGs and abundance of the NOTCH-and mTOR-signaling pathways. The transcript signature of the fourth cluster (including both DNTs and GGs) was related to impaired neural function. Our analysis suggests distinct oncological pathomechanisms in long-term epilepsy-associated tumors. Transcriptional activation of MAPK-pathway and BRAF V600E mutation are associated with an increased risk for tumor recurrence and malignant progression, therefore the treatment of these tumors should integrate both epileptological and oncological aspects. Tumor series derived from epilepsy-surgery programs cover a range of generally rare glial and glioneuronal entities. Among them, gangliogliomas (GGs) and dysembryoplastic neuroepithelial tumors (DNTs) represent the most common glioneuronal tumors causing tumor-related drug-resistant epilepsy in young adults 1. Since epilepsy is the leading clinical symptom of these tumors, GGs and DNTs (together with pleomorphic xanthoastrocytomas, PXAs) are often referred to as long-term epilepsy-associated tumors (LEATs) 2,3. While for common glial entities such as pilocytic astrocytomas (PAs) and PXAs the diagnostic criteria and parameters determining the clinical outcome are well established 4 , the situation is more difficult for glioneuronal tumors. For GGs and DNTs, the neuropathological stratification is particularly complex with high inter-observer variability 5. This is resembled by inconsistent diagnose frequencies, showing variations form 6% to 49% for GGs and 7% to 80% for DNTs in large series 6. Striving for more reliable diagnostic approaches, recent studies started investigating

Background Meningiomas are common brain tumours that are usually defined by benign clinical course. However, some meningiomas undergo a malignant transformation and recur within a short time period regardless of their World Health Organization (WHO) grade. The current study aimed to identify potential markers that can discriminate between benign and malignant meningioma courses. Methods We profiled the metabolites from 43 patients with low- and high-grade meningiomas. Tumour specimens were analyzed by nuclear magnetic resonance analysis; 270 metabolites were identified and clustered with the AutoPipe algorithm. Results We observed two distinct clusters marked by alterations in glycine/serine and choline/tryptophan metabolism. Glycine/serine cluster showed significantly lower WHO grades and proliferation rates. Also progression-free survival was significantly longer in the glycine/serine cluster. Conclusion Our findings suggest that alterations in glycine/serine metabolism are associated with lower proliferation and more recurrent tumours. Altered choline/tryptophan metabolism was associated with increases proliferation, and recurrence. Our results suggest that tumour malignancy can be reflected by metabolic alterations, which may support histological classifications to predict the clinical outcome of patients with meningiomas.