Faculty Bibliography

H3K27 downregulates gene transcription. When H3K27 is trimethylated, it is tightly associated with inactive gene promoters. In malignant gliomas, the loss of histone H3K27 trimethylation is strongly associated with underlying K27M mutation; however the role of H3K27 in meningiomas has not been completely elucidated. Atypical and anaplastic meningiomas (WHO Grade II and III) are associated with higher risk of recurrence following gross total resection; however the molecular biology of anaplastic progression is not completely understood. We performed histological and molecular analysis of 14 WHO Grade II and III meningiomas and compared them with 6 locally invasive WHO Grade I meningiomas. Grade and atypical features were correlated with expression of histone H3K27 trimethylation by immunohistochemistry. Staining intensity (none, weak, moderate, strong) and extent of staining (0-100% of the tumor) were evaluated semi-quantitatively. We also tested the tumors for K27M mutation by mutation specific antibody. Out of 14 high grade meningiomas, 10 showed a complete loss of K27 trimethyl staining and 4 tumors showed small foci of preserved trimethyl staining, mostly in areas close to the dura; however staining intensity was weak. In contrary, all 6 (100%) WHO Grade I tumors showed preserved multifocal trimethyl mark expression in 25-50% of the tumor cells, with moderate (5) or strong (1) staining intensity. All tumors were negative for histone H3K27M mutation by immunohistochemistry. Atypical and anaplastic meningiomas show almost uniform loss of histone H3K27 trimethylation staining. However this loss of trimethylation is not caused by histone H3K27M mutation. Loss of histone H3K27 trimethylation leads to dysregulation of the PRC2 complex, which is involved in repression of non-cell-type specific promoters and may contribute to aggressive behavior. Clinically, loss of histone H3K27 trimethylation can be used as a diagnostic marker for a high grade meningiomaswhen histological features are inconclusive

INTRODUCTION: Optic gliomas are classified as pilocytic astrocytoma (PA) or pilomyxoid astrocytoma (PMXA). Abundant bluish chondroid myxoid matrix is characteristic of PMXA but not PA. We sought to investigate the molecular composition of myxoid matrix and its biologic role in angiogenesis of optic gliomas. We reviewed clinical and pathological data on a cohort of 120 patients with optic glioma diagnosed at NYU Langone Medical Center from 1996 to 2014. We analyzed microvascular density (MVD), perfusion, hypoxia and proliferation by immunohistochemistry and ultrastructural features by electron microscopy. To identify the composition of the myxoid matrix in PMXA we performed liquid chromatography-mass spectrometry (LC-MS) without sample fractionation quantified using peptide spectral counts. PMXA showed significantly lower MVD by CD34 (8.1 vs 14.5, p-value < 0.002) and Erg (7 vs. 13.6, p-value 0.003) than PA, however GLUT-1 showed equal perfusion. Electron microscopy showed that PMXA contain both regular blood vessels with endothelial lining and channels completely lacking endothelial and smooth muscle cells. LC-MS stratified optic gliomas into three distinct groups. We identified 5389 proteins of which 188 were differentially expressed in the three groups (p<0.05, Benjamini-Hochberg adjustment). Between PA and PMXA, we found that most of differentially expressed proteins (146/188) displayed a positive fold change (increasing in PMXA relative to PA), and a minority (42/188) showed a negative fold change. The most abundant extracellular matrix proteins were a chondroitin sulfate proteoglycan versican (VCAN 3.7-fold increase Q=0.000463) and its paralog vertebrate Hyaluronan And Proteoglycan Link Protein 1 (HAPLN1, 22-fold increase from the PA to the PMXA group Q=4.60x10-7). Optic gliomas can develop endothelium-independent channels reminiscent of those in invertebrates to maintain blood supply. The myxoid matrix is composed of VCAN and its linking paralog HAPLN1. Targeting the myxoid matrix may provide novel avenues for therapy of optic gliom

Encephalopathy of prematurity (EOP) is a complex form of cerebral injury that occurs in the setting of either primary or secondary hypoxia-ischemia (HI) in the premature infant. In this study we have investigated in the rat model of EOP whether neonatal HI of the brain may in vivo alter the expression of cystathionine b-synthase (CBS) and the components of the mammalian target of rapamycin (mTOR) signaling pathway. We have performed unilateral carotid ligation and HI (UCL/HI) in Long-Evans rats at P6 and found by western blot and immunohistochemical analyses an increased expression of CBS in the white matter as early as 24 hours (P7) post procedure. CBS remained elevated through P21, and to the lesser extent in early adulthood (P40). All tested mTOR downstream targets (p70S6K and phospho-p70S6K & S6 and phospho-S6) were also overexpressed at the same time points in the UCL/HI rats compared to healthy controls. Importantly, this overexpression of mTOR components was not observed in rats treated with the mTOR inhibitor everolimus. Behavioral assays-open field locomotion test and three-chambered social choice test-performed on young adult rats (P35-37) following UCL/HI at P6, indicated hyperactive behavior and impaired preference for social novelty. Everolimus prevented both of these hall-marks of autism and restored behavioral patterns otherwise observed in healthy controls. Gait analysis has shown motor deficits in the hind paws of UCL/HI rats that were also significantly reduced by everolimus, indicating neurological protection/recovery of treated animals. Our results suggest that neonatal HI brain injury may cause its long term sequelae via upregulation of CBS and mTOR signaling pathway, as recently observed by us in patients with EOP, and propose this signaling cascade as a possible new molecular therapeutic target for this still untreatable cause of later life motor and autism-like behavioral deficits

Pediatric glioblastoma is one of the most common and most deadly brain tumors in childhood. Using an integrative genetic analysis of 53 pediatric glioblastomas and five in vitro model systems, we identified previously unidentified gene fusions involving the MET oncogene in ~10% of cases. These MET fusions activated mitogen-activated protein kinase (MAPK) signaling and, in cooperation with lesions compromising cell cycle regulation, induced aggressive glial tumors in vivo. MET inhibitors suppressed MET tumor growth in xenograft models. Finally, we treated a pediatric patient bearing a MET-fusion-expressing glioblastoma with the targeted inhibitor crizotinib. This therapy led to substantial tumor shrinkage and associated relief of symptoms, but new treatment-resistant lesions appeared, indicating that combination therapies are likely necessary to achieve a durable clinical response.