Hypoxia inducible factors (HIF) are transcription factors regulating expression of several genes related to oxygen homeostasis in response to hypoxic stress. Although HIF1-alpha and platelet derived growth factor-B (PDGF-B) are expressed in glioma tissue and closely related to tumor angiogenesis mediating vascular endothelial growth factor (VEGF) activity, their direct relationship has not yet been clarified. The aim of this study is to investigate whether HIF1-alpha regulates PDGF-B expression. The human glioblastoma cell lines, U87MG, U251MG, and A172, were exposed to 1-21% oxygen for 24 h. PDGF-B mRNA expression were quantitatively analyzed by real time RT-PCR, their intracellular protein levels were determined by computerized image analysis supported by flow cytometry to detect intracellular PDGF-B, and the concentration of secreted PDGF-B protein was assayed by ELIA. We also assayed following transfection of the cells with short interference RNA (siRNA) targeting HIF1-alpha mRNA. Relative PDGF-B mRNA and secretion of PDGF-B protein were significantly elevated at 1% oxygen. Following transfection of HIF1-alpha siRNA at 1% oxygen, PDGF-B expression was significantly suppressed at mRNA level. Our findings indicated that HIF1-alpha up-regulated expression of PDGF-B in human glioblastoma cells and showed the feasibility of siRNA technology in glioblastoma cell lines.

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Hypoxia-inducible factor-1 (HIF-1) alpha is the major transcription factor involved in the adaptive response to hypoxia. The purpose of this study was to investigate whether HIF 1-alpha protects HP75 cells, pituitary adenoma cell line from hypoxia induced apoptosis. HP75 was transfected with siRNA targeting HIF 1-alpha mRNA sequences or scrambled RNA duplexes, followed by subjected to hypoxia (1% oxygen) for 24 h, compared with normoxia (21%). The efficacy of RNAi was assessed via real-time RT-PCR and immunohistochemistry. Apoptosis was determined by Tdt-mediated dUTP nick end-labeling (TUNEL) assay and agarose gel electrophoresis. Membrane cDNA microarray was examined to detect gene profiling among the cell in normoxia, hypoxia, or hypoxia following the RNAi. A significantly greater proportion of HP75 cells transfected with specific siRNA duplexes and subsequently exposed to hypoxia demonstrated apoptosis to a large extent when compared with non-transfected cells. Transfection with specific siRNA duplexes knocked down HIF 1-alpha mRNA and protein expression in hypoxia-exposed cells by approximately 80%, whereas transfection with scrambled siRNA duplexes had no noticeable effect on HIF 1-alpha expression. Microarray analysis indicated that HIF1-alpha down-regulated caspase-10. These findings strongly suggest that HIF 1-alpha exerts an antiapoptotic role in HP75 in hypoxia.

Pleomorphic xanthoastrocytoma has been generally conceived to be in a benign nature, showing a relatively favorable prognosis. Apoplectic attack attributable by massive hemorrhage in this distinct form of the supratentorial glioma is an exceedingly rare event. A 61-year-old female presented with a sudden onset of generalized tonic--clonic convulsion. CT and MRI disclosed the presence of a tumor composing of massive intra-tumoral hemorrhage filling the cyst associated with mural nodule in the left frontotemporal lobe. At surgery, the subpial mass involving hematoma was well marginated and slightly adherent to the dura mater. It could be removed totally and proved to be a pleomorphic xanthoastrocytoma. The unusual hemorrhagic presentation of this typically benign entity is extremely rare and is thought to be intra-tumoral bleeding in this case, since subarachnoid hemorrhage was absent.

Persistent expression of green fluorescent protein (GFP) in human malignant glioma cell clones (U87MG, U251MG, and U373MG) was established using the pEGFP-Cl vector. Tumor spheroid was implanted into the caudate nucleus-putamen of a severely compromised immunodeficient (SCID) mouse brain slice. To allow quantitative assessment of tumor cell invasion, the invasion area index was measured on days 1, 3, 5, and 7 by a fluorescence stereomicroscope and an image analyzer in the presence of varying concentrations of SI-27. In the control group (0 microg/ml), all glioma cell lines invaded in a fingerlike fashion, reaching the contralateral hemisphere via the corpus callosum. SI-27 at concentrations of 10, 50, or 100 microg/ml significantly suppressed the index on days 5 and 7 in a dose-dependent manner, whereas 1 microg/ml had no effect. Laser confocal microscopy indicated that the tumor cells penetrated through the brain slice. This model enabled unequivocal periodic tracking of individual invading tumor cells in the normal brain. The significant suppression of glioma cell invasion by SI-27 indicates that anti-matrix metalloproteinase (MMP) treatment may represent an important future therapeutic strategy for malignant cerebral neoplasms.