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Transcriptional Characterization of Glioma Neural Stem Cells Diva ...

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7.3 Tumour Expression Correlation Results<br />

regulation <strong>of</strong> its expression in GNS cell lines opposed to its up-regulation in<br />

primary GBM (Fig 7.4c), and a strong down-regulation in grade III astrocy-<br />

toma (Fig 7.4d).<br />

The HMGA2 gene encodes a transcriptional regulator that belongs to the non-<br />

histone family <strong>of</strong> structural proteins. The members <strong>of</strong> this family act as chro-<br />

matin architectural factors and contain structural DNA-binding domains that<br />

allow them to act as transcriptional factors. We find HMGA2 to be down-<br />

regulated in GNS lines and up-regulated in primary GBM (Fig 7.4c), and<br />

slightly down-regulated in grade III astrocytoma (Fig 7.4d). Low or absent<br />

protein expression <strong>of</strong> HMGA2 has been observed in GBM compared to low<br />

grade gliomas [14] and HMGA2 polymorphisms have been associated with<br />

survival time in GBM [295].<br />

The SDC2 gene encodes a transmembrane heparan sulfate proteoglycan that<br />

participates as an extracellular matrix receptor in the processes <strong>of</strong> cell prolifera-<br />

tion, cell migration and cell-matrix interaction. An altered expression <strong>of</strong> SDC2<br />

has been detected in esophageal carcinoma [201], colon carcinoma [184], fi-<br />

brosarcoma [380], prostate cancer [108,407] and gliomas, where over-expression<br />

<strong>of</strong> SDC2 promotes membrane protrusion, migration, capillary tube formation<br />

and cell-cell interactions in microvascular endothelial cells [141]. We found<br />

SDC2 to be down-regulated in GNS cell lines and grade III astrocytoma, but<br />

slightly up-regulated in primary GBM (Fig 7.4).<br />

The SYNM gene is a type IV intermediate filament that has recently been<br />

shown to interact with the LIM domain protein Zyxin, thereby possibly mod-<br />

ulating cell adhesion and cell motility. Aberrant SYNM promoter methylation<br />

has been associated with early breast cancer relapse [362]. In gliomas SYNM<br />

has been found to promote AKT-dependent GBM cell proliferation by antago-<br />

nising protein phosphatase PP2A, the major regulator <strong>of</strong> Akt dephosphoryla-<br />

tion [396]. We found SYNM to be down-regulated in GNS cell lines and grade<br />

III astrocytoma, but slightly up-regulated in primary GBM, although with a<br />

relatively high p-value (Fig 7.4). The IRX2 gene is a iroquois-class homeobox<br />

genes that has been associated with development <strong>of</strong> the vertebrate embryo<br />

and in humans specifically in the development <strong>of</strong> brain [322] and breast [274].<br />

Over-expression <strong>of</strong> IRX2 has been detected in s<strong>of</strong>t tissue sarcomas [7]. IRX2<br />

has been proposed to enhance antitumour immune responses in that ex vivo<br />

pre-treatment <strong>of</strong> CD8 + T cells with IRX-2 provided protection from tumour-<br />

induced apoptosis [112]. In line with this suggested role <strong>of</strong> IRX2, we observed<br />

the gene to be strongly down-regulated in GNS cell lines and grade III astro-<br />

179

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