The D2HG product of IDH1 may increase neuronal activity by mimicking the activity of glutamate on the NMDA receptor, and IDH1 gliomas are more likely to cause seizures in patients. This has rapid translational implications for the personalized management of tumor-associated epilepsy, as targeted IDH1 inhibitors may improve antiepileptic therapy in patients with IDH1 gliomas.

Mutant isocitrate dehydrogenase 1 (IDH1) is common in gliomas, and produces D-2-hydroxyglutarate (D-2-HG). The full effects of IDH1 mutations on glioma biology and tumor microenvironment are unknown. We analyzed a discovery cohort of 169 World Health Organization (WHO) grade II-IV gliomas, followed by a validation cohort of 148 cases, for IDH1 mutations, intratumoral microthrombi, and venous thromboemboli (VTE). 430 gliomas from The Cancer Genome Atlas were analyzed for mRNAs associated with coagulation, and 95 gliomas in a tissue microarray were assessed for Tissue Factor (TF) protein. In vitro and in vivo assays evaluated platelet aggregation and clotting time in the presence of mutant IDH1 or D-2-HG. VTE occurred in 26–30% of patients with wild-type IDH1 gliomas, but not in patients with mutant IDH1 gliomas (0%). IDH1 mutation status was the most powerful predictive marker for VTE, independent of variables such as GBM diagnosis and prolonged hospital stay. Microthrombi were far less common within mutant IDH1 gliomas regardless of WHO grade (85–90% in wild-type versus 2–6% in mutant), and were an independent predictor of IDH1 wild-type status. Among all 35 coagulation-associated genes, F3 mRNA, encoding TF, showed the strongest inverse relationship with IDH1 mutations. Mutant IDH1 gliomas had F3 gene promoter hypermethylation, with lower TF protein expression. D-2-HG rapidly inhibited platelet aggregation and blood clotting via a novel calcium-dependent, methylation-independent mechanism. Mutant IDH1 glioma engraftment in mice significantly prolonged bleeding time. Our data suggest that mutant IDH1 has potent antithrombotic activity within gliomas and throughout the peripheral circulation. These findings have implications for the pathologic evaluation of gliomas, the effect of altered isocitrate metabolism on tumor microenvironment, and risk assessment of glioma patients for VTE.

Giant-cell tumours of the sacrum are difficult to treat. Surgery carries a high risk of morbidity, local recurrence and mortality. Radiation is effective in some patients, but has a risk of malignant change. We evaluated the effectiveness of serial arterial embolisation as an alternative to surgery. Five patients with giant-cell tumours of the sacrum which had been primarily treated by serial embolisation were retrospectively reviewed for changes in the size of the tumour. In four the symptoms resolved with full return of function and arrest in the growth of the tumour. They remained free from growth, recurrence, or metastases at follow-up (4 to 17 years). One patient died from metastatic disease within 18 months of the initial diagnosis.

Giant-cell tumours of the sacrum are difficult to treat. Surgery carries a high risk of morbidity, local recurrence and mortality. Radiation is effective in some patients, but has a risk of malignant change. We evaluated the effectiveness of serial arterial embolisation as an alternative to surgery. Five patients with giant-cell tumours of the sacrum which had been primarily treated by serial embolisation were retrospectively reviewed for changes in the size of the tumour. In four the symptoms resolved with full return of function and arrest in the growth of the tumour. They remained free from growth, recurrence, or metastases at follow-up (4 to 17 years). One patient died from metastatic disease within 18 months of the initial diagnosis.

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