RBIO-04. FRACTAL STRUCTURE IN THE VOLUMETRIC CONTRAST ENHANCEMENT OF MALIGNANT GLIOMAS AS A MARKER OF OXIDATIVE METABOLIC PATHWAY GENE EXPRESSION

Abstracts and NICD1 increased 1.3 ± 0.1-fold (p<0.005) in irradiated explants. Neither marker increased in irradiated HGG specimens treated with LY364947. Our study demonstrates the utility of implementing explants for patient screening, while the apparent benefit of TGF-β inhibition in most irradiated HGG specimens provides further support for clinical trials of TGF-β inhibition during radiotherapy. BACKGROUND: Of the many treatment options, gemcitabine has been currently used clinically to a variety of solid tumors types both as a chemotherapeutic agent and as a radiation sensitizer. However, it has been speculated that the gemcitabine plus relatively high dose of radiation increased the toxicity. Therefore, our current approaches to integrate of molecularly targeted agents, which potentially produce less toxicity than standard chemotherapy, and with gemcitabine-radiation improve chemo-radiation sensitivity. METHODS: We combined HDACs or Chk1 inhibitors with gemcitabine and radiation using three meningioma cell lines (Ben Men 1, CH157 MN, and IOMM-Lee). These cell lines were treated with the 1 µM of HDAC inhibitor (Ganoderic Acid A and DM) or 1 µM of Chk1 inhibitor (UCN-01 and SB218078) with 1 µM of gemcitabine plus irradiation (1 Gy single dose) for 72 hr. Cell proliferation (SRB assay), cell survival (clonogenic assay) and apoptosis (Western blot) were analyzed following treatments. RESULTS: Our in vitro studies demonstrated that HDAC inhibitors Ganoderic Acid (A and DM) andChk1 inhibitor UCN-01 and SB218078 enhances gemcitabine + radiation activity, likely via disruption of HDAC activities and Chk1 signaling and inducing caspase-3 activities. These studies also indicate that timing of drug administration strongly influences response to gemcitabine + radiation activity plus HDAC inhibitor or Chk1 inhibitor in all three meningioma cells. Furthermore, this sequence combination was more effective in cell lines with dysfunctional Chk1 signaling or low level of HDAC activity. Addition of HDAC inhibitor or Chk1 inhibitor to gemcitabine significantly enhanced inhibition of cell proliferation and inhibited the gemcitabine and RT mediated apoptotic cascade. RBIO-04. FRACTAL STRUCTURE IN THE VOLUMETRIC CONTRAST ENHANCEMENT OF MALIGNANT GLIOMAS AS A MARKER OF OXIDATIVE METABOLIC PATHWAY GENE EXPRESSION Kai Miller1, Sharon Berendsen2, Tatjana Seute2, Kristen Yeom1, Melanie Gephardt1, Gerald Grant1 and Pierre Robe2,3; 1Stanford University, Stanford, CA, USA, 2UMC Utrecht, Utrecht, Netherlands, 3University of Liège, Liège, Belgium INTRODUCTION: Fractal structure is found throughout many processes in nature, and often arises from sets of simple rules. We examined the contrast enhancement patterns in MRI scans from glioblastoma patients for evidence of fractal structure and correlated these with gene expression patterns. METHODS: For 39 glioblastoma patients, volumetric T1 post-contrast MRI scans were obtained before surgical resection. For each tumor, we calculated the fractal dimension (Minkowski–Bouligand dimension) of contrast enhancement with a box-counting (cubic scaling) approach. RNA expression microarray data from resected tissue were explored by gene set enrichment analysis (GSEA), and VEGF expression level was determined by antibody staining of resected tissue. RESULTS: We found robust evidence for fractal structure in the contrast enhancement pattern, with an average fractal dimension of 2.17 ± 0.10, with a visually apparent split at 2.10. GSEA analysis showed a clear association between this split in fractal dimension and 6 gene sets (of 4080), all 6 of which are linked to mitochondrial respiration/ATP production pathways. Higher fractal dimension (>2.10) was associated with decreased gene expression in all cases. VEGF expression was correlated with higher fractal dimension. CONCLUSION: There is fractal structure in the volumetric enhancement pattern of glioblastomas, with dimension approximately 2.15. Variation in this fractal dimension, and therefore the complexity of contrast enhancement it reflects, is specifically associated with genetic correlates of a shift to glycolytic metabolism in tumor cells. Drugs that shift glioblastoma to oxidative metabolism have recently been RBIO-05. miRNAs THAT CONFER GLIOBLASTOMA RESISTANCE: IS THE COMBINATION MERELY A SUM OF THE PARTS? Clark Chen1, Patryk Moskwal2, Pascal Zinn2, Young Eun Choi2, Sachet Shukla2, Wojciech Fendler2, Jun Lu3, Todd Golub2, Anita Hjelmeland2 and Dipanjan Chowdhury2; 1University of California San Diego, Department of Neurosurgery, La Jolla, CA, USA, 2DFCI, Boston, MA, USA, 3Yale Medical School, New Haven, CT, USA INTRODUCTION: Most studies of miRNA focus on the biology of single miRNA. How miRNAs interact with one another to modulate complex biologic effects, such as radiation resistance, remain poorly understood. METHODS: An unbiased functional microRNA screen identified four miRNAs (miR1, miR125a, miR150, and miR425) that, when expressed together, induced glioblastoma radioresistance. We employed gain and loss of function approaches to validate the critical importance of these miRNAs as determinants of glioblastoma radiation resistance. RESULTS: Coexpression of miR1, miR125a, miR150, and/or miR425 in glioblastoma promotes radioresistance through upregulation of the cell-cycle checkpoint response. Such effects were not seen when each miRNA mimic was expressed individually. Antagonizing with antagomiRs sensitizes glioblastoma cells to irradiation, suggesting their potential as targets for inhibiting therapeutic resistance. Analysis of glioblastoma datasets from The Cancer Genome Atlas (TCGA) revealed that these miRNAs are expressed in glioblastoma patient specimens and correlate with TGFb signaling. Supporting this hypothesis, the expression of miR1 and miR125a can be induced by TGFb and antagonized by a TGFb receptor inhibitor. Together, these results provide insight into the therapeutic application of TGFb inhibitors in radiotherapy. CONCLUSION: Through an unbiased, systematic screen designed to identify miR combinations that confer glioblastoma radiation resistance, we uncovered a novel miRNA combination. The effects of the four miRNAs in aggregate was distinct from that seen with each individual siRNAs. The study points to the importance of an integrated study of miRNA combinations relative to the characterization of each individual miRNAs. RBIO-06. CROSSTALK OF ErbB2 WITH LEF1 REGULATES JAGGED1MEDIATED RADIORESISTANCE IN GLIOBLASTOMA Divya Kesanakurti1, Jihong Xu1, Balveen Kaur2, Vinay Puduvalli3 and Alessandro Canella1; 1Division of Neuro-oncology, Department of Neurosurgery, The Dardinger Center for Neuro-oncology Research, The Ohio State University Comprehensive Cancer Center, Columbus, OH, USA, 2Dardinger Laboratory for Neuro-oncology and Neurosciences, Department of Neurological Surgery, College of Medicine, The Ohio State University, Columbus, OH, USA, 3Ohio State University Medical Center (...truncated)