Tumor regression and angiogenesis inhibition by phenyl-tert-butyl nitrone and its main metabolite in C6 rat glioma model

5480 Prognosis of patients who are diagnosed with Glioblastoma multiforme, the most common type of primary brain tumors, is still very poor, because of the difficulty of an early and accurate diagnosis and of the lack of efficient therapeutic drugs. Magnetic resonance imaging (MRI) and angiography (MRA) can be used as non-invasive in vivo imaging modalities that can assess morphology and growth characteristics as well as angiogenic behavior of gliomas, and perhaps provide better diagnosis. New treatments are also sought, that would have an effect on well-established and vascularized tumors. MRI and MRA were used to evaluate the morphological and angiogenic properties of C6 rat glioma model, and to assess the efficiency of an antioxidant treatment, phenyl-tert-butyl nitrone (PBN), and of its main metabolite, 4-hydroxy-PBN (4OH-PBN), on this glioma model. C6 cells (10,000 cells) were injected intracranially into the cortex (2mm from midline, 2mm anterior to bregma, at a depth of 3mm) of male Fischer 344 rats fed a choline-deficient diet. PBN or 4OH-PBN (75mg/kg/day in drinking water) treatment was started at different time points before and after cell implantation. MRI and MRA (time-of-flight technique) data was acquired at 7 Tesla at day 7 and then every third day until day 40 or death of the rat. Glioma morphologies and volumes were assessed by T1/T2-weighted images, and doubling time was calculated for each treatment group. Blood volume and vasculature projections were obtained in the tumor region of interest using MRA data and a Mathematica-based program. Finally, histology (H&E) and immunostaining assays (von Willebrand factor, synaptophysin and VEGF) were conducted for each animal. MR results showed the diffusive invasiveness of C6 gliomas, which preferentially used pre-existing blood vessels for their nutrient sources. These results rival those from histology and immunostaining evaluations. PBN has also been found to clearly induce a decrease of the growth rate and tumor regression, while inhibiting neovascularization. It even had a 40% efficiency in reducing well-established tumors. 4OH-PBN efficiency was less pronounced, as only one third of the gliomas responded to a pre-treatment. MRI and MRA are useful in vivo imaging tools to diagnose gliomas and evaluate therapeutic agents, such as PBN, which clearly inhibits glioma growth and angiogenesis in C6 rat glioma model. Funds were appreciated from NIH P20RR016478 grant.