title: The peripheral-type benzodiazepine receptor and tumorigenicity: isoquinoline binding protein (IBP) antisense knockdown in the C6 glioma cell line.
abstract: Peripheral-type benzodiazepine receptors (PBR) are constituted by three protein components, the isoquinoline binding protein (IBP), the voltage-dependent anion channel (VDAC), and the adenine nucleotide transporter (ANT). Recently, we found that high levels of PBR ligand binding in glioma cell lines correlate with in vitro tumorigenicity. To study whether enhanced PBR expression is causative or in response to cancer, we genetically modified C6 glioma cells. Antisense knockdown of the IBP resulted in more than 50% reductions in PBR ligand binding both in the mitochondrial and whole cell fractions, accompanied by similar reductions in IBP levels in these respective fractions. The IBP knockdown was accompanied by a 25% increase in cell number in confluent cultures. This correlated with an 8-fold increase in in vitro tumorigenicity, as assessed by anchorage independent growth. Cell cycle analysis indicated that knockdown of the IBP resulted in a 60% reduction in the number of cells in the pre-G1 apoptosis phase. This paralleled the reduction seen in apoptosis and cell death shown by DNA fragmentation and Trypan blue assays, respectively. Furthermore, knockdown of the IBP appeared to prevent induction of apoptosis by the antineoplastic agent, erucylphosphocholine. In addition, IBP knockdown prevented processing of the caspase 3 component of the apoptosis cascade by the erucylphosphocholine congener, erucylphospho-N,N,N-trimethylammonium. In conclusion, our results suggest that enhanced IBP expression, including enhanced PBR ligand binding, such as occurring in untreated C6 glioma cells, may provide a mechanism to increase apoptotic rates of cancer cells.
authors: Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa, Israel.
authors: Evgeny
authors: E
authors: Levin
authors: Arumugam
authors: A
authors: Premkumar
authors: Leo
authors: L
authors: Veenman
authors: Wilfried
authors: W
authors: Kugler
authors: Svetlana
authors: S
authors: Leschiner
authors: Ilana
authors: I
authors: Spanier
authors: Gary
authors: G
authors: Weisinger
authors: Max
authors: M
authors: Lakomek
authors: Abraham
authors: A
authors: Weizman
authors: Solomon H
authors: SH
authors: Snyder
authors: Gavril W
authors: GW
authors: Pasternak
authors: Moshe
authors: M
authors: Gavish
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002452:Cell Count; D045744:Cell Line, Tumor; D002999:Clone Cells; D016373:DNA, Antisense / Q000737:chemistry; D058787:GABA-A Receptor Antagonists; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D051381:Rats; D011963:Receptors, GABA-A / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D014162:Transfection; D014343:Trypan Blue
chemical_list: D002352:Carrier Proteins; D016373:DNA, Antisense; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D010767:Phosphorylcholine; C069997:Tspo protein, rat; C075010:erucylphosphocholine; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D014343:Trypan Blue