Tumour-associated glial host cells display a stem-like phenotype with a distinct gene expression profile and promote growth of GBM xenografts.
BACKGROUND
Little is known about the role of glial host cells in brain tumours. However, supporting stromal cells have been shown to foster tumour growth in other cancers.


METHODS
We isolated stromal cells from patient-derived glioblastoma (GBM) xenografts established in GFP-NOD/scid mice. With simultaneous removal of CD11b+immune and CD31+endothelial cells by fluorescence activated cell sorting (FACS), we obtained a population of tumour-associated glial cells, TAGs, expressing markers of terminally differentiaed glial cell types or glial progenitors. This cell population was subsequently characterised using gene expression analyses and immunocytochemistry. Furthermore, sphere formation was assessed in vitro and their glioma growth-promoting ability was examined in vivo. Finally, the expression of TAG related markers was validated in human GBMs.


RESULTS
TAGs were highly enriched for the expression of glial cell proteins including GFAP and myelin basic protein (MBP), and immature markers such as Nestin and O4. A fraction of TAGs displayed sphere formation in stem cell medium. Moreover, TAGs promoted brain tumour growth in vivo when co-implanted with glioma cells, compared to implanting only glioma cells, or glioma cells and unconditioned glial cells from mice without tumours. Genome-wide microarray analysis of TAGs showed an expression profile distinct from glial cells from healthy mice brains. Notably, TAGs upregulated genes associated with immature cell types and self-renewal, including Pou3f2 and Sox2. In addition, TAGs from highly angiogenic tumours showed upregulation of angiogenic factors, including Vegf and Angiopoietin 2. Immunohistochemistry of three GBMs, two patient biopsies and one GBM xenograft, confirmed that the expression of these genes was mainly confined to TAGs in the tumour bed. Furthermore, their expression profiles displayed a significant overlap with gene clusters defining prognostic subclasses of human GBMs.


CONCLUSIONS
Our data demonstrate that glial host cells in brain tumours are functionally distinct from glial cells of healthy mice brains. Furthermore, TAGs display a gene expression profile with enrichment for genes related to stem cells, immature cell types and developmental processes. Future studies are needed to delineate the biological mechanisms regulating the brain tumour-host interplay.
Neuro Clinic, Haukeland University Hospital, Bergen, Norway.|Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.
Lina
L
Leiss
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway. ercmut86@gmail.com.
Ercan
http://orcid.org/0000-0002-2513-4764
E
Mutlu
Department of Clinical Science, University of Bergen, Bergen, Norway.|Department of Microbiology and Immunology, Haukeland University Hospital, Bergen, Norway.
Anne
A
Øyan
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.|Department of Neurosurgery, Qilu Hospital of Shandong University, Jinan, China.|Brain Science Research Institute, Shandong University, 107# Wenhua Xi Road, Jinan, 250012, People's Republic of China.
Tao
T
Yan
Department of Clinical Science, University of Bergen, Bergen, Norway.
Oleg
O
Tsinkalovsky
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.
Linda
L
Sleire
Computational Biology Unit, Uni Computing, Uni Research AS, Bergen, Norway.
Kjell
K
Petersen
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.
Mohummad Aminur
MA
Rahman
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.
Mireille
M
Johannessen
Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California, USA.
Sidhartha S
SS
Mitra
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.
Hege K
HK
Jacobsen
Translational Cancer Research Group, Department of Biomedicine, University of Bergen, Bergen, Norway.
Krishna M
KM
Talasila
Translational Cancer Research Group, Department of Biomedicine, University of Bergen, Bergen, Norway.|Department of Clinical Medicine, Haukeland University Hospital, Bergen, Norway.
Hrvoje
H
Miletic
Computational Biology Unit, Uni Computing, Uni Research AS, Bergen, Norway.|Department of Informatics, University of Bergen, Bergen, Norway.
Inge
I
Jonassen
Department of Neurosurgery, Qilu Hospital of Shandong University, Jinan, China.|Brain Science Research Institute, Shandong University, 107# Wenhua Xi Road, Jinan, 250012, People's Republic of China.
Xingang
X
Li
Core Facility Flow Cytometry, Centre de Recherche Public de la Santé (CRP-Santé), L-1526, Luxembourg, Luxembourg.
Nicolaas H
NH
Brons
Department of Clinical Science, University of Bergen, Bergen, Norway.|Department of Microbiology and Immunology, Haukeland University Hospital, Bergen, Norway.
Karl-Henning
KH
Kalland
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.|Department of Neurosurgery, Qilu Hospital of Shandong University, Jinan, China.|Brain Science Research Institute, Shandong University, 107# Wenhua Xi Road, Jinan, 250012, People's Republic of China.
Jian
J
Wang
Oncomatrix Research Lab, Department of Biomedicine, University of Bergen, Bergen, Norway.|Department of Neurosurgery, Haukeland University Hospital, Bergen, Norway.
Per Øyvind
PØ
Enger
D000818:Animals; D014408:Biomarkers, Tumor; D001921:Brain / Q000378:metabolism*; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D046228:Microarray Analysis; D059467:Transcriptome; D023041:Xenograft Model Antitumor Assays
D014408:Biomarkers, Tumor
GFF-NOD/scid mice; Gene expression analysis; Glioblastoma; POU3F2; Stem cell markers; Tumour-associated glial cells; Tumour-host interplay; Xenograft tumours