Radiation Responses of 2D and 3D Glioblastoma Cells: A Novel, 3D-specific Radioprotective Role of VEGF/Akt Signaling through Functional Activation of NHEJ.

Glioblastoma is resistant to conventional treatments and has dismal prognosis. Despite promising in vitro data, molecular targeted agents have failed to improve outcomes in patients, indicating that conventional two-dimensional (2D) in vitro models of GBM do not recapitulate the clinical scenario. Responses of primary glioblastoma stem-like cells (GSC) to radiation in combination with EGFR, VEGF, and Akt inhibition were investigated in conventional 2D cultures and a three-dimensional (3D) in vitro model of GBM that recapitulates key GBM clinical features. VEGF deprivation had no effect on radiation responses of 2D GSCs, but enhanced radiosensitivity of GSC cultures in 3D. The opposite effects were observed for EGFR inhibition. Detailed analysis of VEGF and EGF signaling demonstrated a radioprotective role of Akt that correlates with VEGF in 3D and with EGFR in 2D. In all cases, positive correlations were observed between increased radiosensitivity, markers of unrepaired DNA damage and persistent phospho-DNA-PK nuclear foci. Conversely, increased numbers of Rad51 foci were observed in radioresistant populations, indicating a novel role for VEGF/Akt signaling in influencing radiosensitivity by regulating the balance between nonhomologous end-joining and homologous recombination-mediated DNA repair. Differential activation of tyrosine kinase receptors in 2D and 3D models of GBM explains the well documented discrepancy between preclinical and clinical effects of EGFR inhibitors. Data obtained from our 3D model identify novel determinants and mechanisms of DNA repair and radiosensitivity in GBM, and confirm Akt as a promising therapeutic target in this cancer of unmet need.

The Prevalence of Cerebrovascular Abnormalities Detected in Various Diagnostic Subgroups of Spontaneous Subarachnoid Hemorrhage in the Modern Era.

OBJECTIVE: To determine prevalence of cerebrovascular abnormalities in diagnostic subgroups of spontaneous subarachnoid hemorrhage (SAH) in a regional neurosurgical center in the modern era. METHODS: Data of 609 consecutive patients with spontaneous SAH in a 3-year period (August 2010 to August 2013) were prospectively collected. Patients were divided into 3 diagnostic subgroups: computed tomography (CT) positive for SAH; CT negative but positive cerebrospinal fluid examination by spectrophotometry for SAH; CT negative for SAH and inconclusive cerebrospinal fluid examination. All patients fit for intervention underwent CT angiography with or without digital subtraction angiography to identify vascular abnormalities for subsequent treatment. RESULTS: Of 609 patients, 554 were fit for further investigation and consideration of further intervention; 514 patients had confirmed SAH. Mean patient age was 54.0 years; 61.5% of patients were women. Of patients, 390 (75.9%) showed vascular abnormalities on angiography. There were 438 patients (85.2%) with confirmed SAH diagnosed on CT scan (group 1). Vascular abnormalities were detected in 81.1% of patients; 18.9% of patients with positive CT scan had no identifiable cause of SAH. Of patients with confirmed SAH, 76 (14.8%) had negative CT scan but positive lumbar puncture (group 2); 46.1% of patients in this group had vascular abnormalities. Three patients with inconclusive cerebrospinal fluid examination had lesions requiring treatment. Median length of hospital stay in group 1 patients was longer than median length of hospital stay in group 2 patients. CONCLUSIONS: Frequency of vascular abnormalities in spontaneous SAH is lower than the traditionally quoted figure, which has diagnostic and prognostic implications for patient management.