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Transcriptional Characterization of Glioma Neural Stem Cells Diva ...

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9.1. Digital Pr<strong>of</strong>iling <strong>of</strong> GNS Cell Lines Discussion<br />

morphogenetic proteins that plays a key role in the transformation <strong>of</strong> mes-<br />

enchymal cells into bone and cartilage [245], and ERBB2, HLA-A and PTEN.<br />

We found that 226 <strong>of</strong> the approx. 2,000 differentially expressed is<strong>of</strong>orms hosted<br />

at least one microRNA seed sequence between at least two tags, which identi-<br />

fied microRNA regulation as a widely adopted mechanism <strong>of</strong> regulation <strong>of</strong> gene<br />

and is<strong>of</strong>orm expression in GNS cell lines. An important follow-up experiment<br />

for which data came in only recently in our laboratory, is the measurement <strong>of</strong><br />

microRNA expression levels in our GNS cell lines on a microRNA microarray<br />

platform. Analysis <strong>of</strong> this data revealed that, <strong>of</strong> the 226 microRNAs identified<br />

on a prediction basis as regulators <strong>of</strong> is<strong>of</strong>orms within our GNS study, miR-<br />

10b (see discussion above) and miR-26a were consistently up-regulated in our<br />

GNS cell lines, and miR-137, miR 128, miR-34a, miR-129-3p, and miR-451<br />

consistently down-regulated, in line with the glioblastoma microRNA litera-<br />

ture [96,278,364].<br />

In the assessment <strong>of</strong> the regulation potentially performed by long non-coding<br />

RNAs, we found 18 up-regulated and 7 down-regulated putative ncRNAs, three<br />

<strong>of</strong> which are known to be long antisense RNAs: CDKN2BAS, HOTAIRM1<br />

and NEAT1. Although long-non coding RNA regulation still needs to be<br />

thoroughly elucidated, an interesting pattern was observed with the levels <strong>of</strong><br />

expression <strong>of</strong> HOTAIRM1 in our GNS cell lines and the expression trend found<br />

in literature in human NB4 promyelocytic cell lines. In fact, upon induction<br />

<strong>of</strong> granulocytic differentiation, HOTAIRM1 becomes strongly up-regulated in<br />

human NB4 promyelocytic cell lines and normal hematopoietic cells, and its<br />

knock-down in NB4 cells causes down-regulation <strong>of</strong> the HOXA1 and HOXA4<br />

genes [547]. In line with these observations, HOTAIRM1 is found to be up-<br />

regulated in our GNS cell lines compared to our NS lines, and the HOXA1 and<br />

HOXA4 genes are also up-regulated (Fig 6.22), which potentially identifies<br />

them as conserved targets <strong>of</strong> HOTAIRM1, although an immuno-precipitation<br />

assay should be performed in order to conclude that.<br />

Overall, in this thesis I demonstrate that our results support GNS lines as<br />

suitable model for understanding the molecular basis <strong>of</strong> glioblastoma, and use<br />

<strong>of</strong> NS cell lines as controls in this setting. By this approach, we have identified<br />

several likely oncogenes and tumour suppressors that have not previously been<br />

associated with glioblastoma. With the advent <strong>of</strong> GNS cell lines, the glioblas-<br />

toma research field is bound to be enriched by experiments that will represent<br />

230

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