Transcriptional Characterization of Glioma Neural Stem Cells Diva ...

7.3 Tumour Expression Correlation Results
The PRSS12 gene encodes a protease that can activate tissue plasminogen acti-
vator (tPA) [335], an enzyme which is highly expressed by glioma cells and has
been suggested to promote invasion [168]. We observe a slight up-regulation
in the GNS cell lines and primary GBM of PRSS12 (Fig 7.4a), and a slight
down-regulation in grade III astrocytomas (Fig 7.4b).
The LYST gene encodes a vesicular transport protein called the "lysosomal
trafficking regulator" that so far has not been implicated in any neoplasia but
is known to be associated with a rare recessive disorder (Chédiak-Higashi syn-
drome) caused by a microtubule polymerisation defect that decreases phago-
cytosis ability [87]. In line with the hypothetical increase of cellular activities
and rates, and thus of vesicular transport, in GNS cells, we observed LYST to
be up-regulated in GNS cell lines and primary GBM (Fig 7.4a), and slightly
down-regulated in grade III astrocytomas (Fig 7.4b).
Down-regulated in GNS cell lines. The panels c and d of figure 7.4 the core
down-regulated genes found through Tag-seq are used to evaluate the compar-
ison of the GBM data to the non-neoplastic tissue data (TCGA dataset), and
the comparison of the GBM (grade IV) to the grade III astrocytoma (HGG
dataset). In this comparison the genes that were also identified via qRT-PCR
as being differentially expressed between GNS cell lines and NS cell lines, are
highlighted by the blue colour gradient dots. The trends highlighted in figure
7.4 show matching down-regulation for genes NELL2, TUSC3, ST6GALNAC5,
PLCH1, NDN, MAP6 and PTEN in GNS cell lines and primary GBM, and non
matching down-regulation in GNS cell lines and up-regulation in primary GBM
for genes MAF, MYL9, HMGA2, SDC2, SYNM, IRX2, TES and TAGLN.
The MAF gene encodes a transcription factor and oncoprotein that belongs to
the same AP-1 super-family of JUN and FOS. MAF has been associated with
multiple myeloma whereby its up-regulation is suggested to enhance myeloma
proliferation and adhesion to the bone marrow [406]. Although not previously
linked to glioma, we find MAF to be down-regulated in GNS cell lines but
slightly up-regulated in primary GBM, perhaps as an indicator of its cell type
restricted proliferation enhancing functions (Fig 7.4c). Accordingly, we ob-
served a slight down-regulation of MAF in grade III astrocytoma with respect
to primary GBM (Fig 7.4d).
The protein encoded by the MYL9 gene is a myosin light chain that has
previously been associated with the stem cell component of lung adenocar-
cinoma [447] and medullary breast cancer [54] in gene expression profiling
studies. MYL9 has never been implicated in glioma and we observed down-
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