A Mouse Model of Human Primitive Neuroectodermal Tumors Resulting from Microenvironmentally-Driven Malignant Transformation of Orthotopically Transplanted Radial Glial Cells

Abstract

There is growing evidence and a consensus in the field that most pediatric brain tumors originate from stem cells, of which radial glial cells constitute a subtype. Here we show that orthotopic transplantation of human radial glial (RG) cells to the subventricular zone of the 3rd ventricle - but not to other transplantation sites - of the brain in immunocompromised NOD-SCID mice, gives rise to tumors that have the hallmarks of CNS primitive neuroectodermal tumors (PNETs). The resulting mouse model strikingly recapitulates the phenotype of PNETs. Importantly, the observed tumorigenic transformation was accompanied by aspects of an epithelial to mesenchymal transition (EMT)-like process. It is also noteworthy that the tumors are highly invasive, and that they effectively recruit mouse endothelial cells for angiogenesis. These results are significant for several reasons. First, they show that malignant transformation of radial glial cells can occur in the absence of specific mutations or inherited genomic alterations. Second, they demonstrate that the same radial glial cells may either give rise to brain tumors or differentiate normally depending upon the microenvironment of the specific region of the brain to which the cells are transplanted. In addition to providing a prospect for drug screening and development of new therapeutic strategies, the resulting mouse model of PNETs offers an unprecedented opportunity to identify the cancer driving molecular alterations and the microenvironmental factors that are responsible for committing otherwise normal radial glial cells to a malignant phenotype.

Characterization of brain tumor initiating cells isolated from an animal model of CNS primitive neuroectodermal tumors

“…We documented previously that RG cells were unable to generate tumors when injected into the motor cortex or the cerebellum of NOD-SCID mice in contrast to the SVZ of the 3 rd ventricle, which resulted in tumors that extensively invaded the brain and the ventricular system [ 7 ]. We now report invading tumor cells in different parts of the mouse brain after TCLs injection into the motor cortex or the cerebellum ( Supplementary Figure 1 ).…”

“…It is conceivable that the up- regulation of these epigenetic regulators may be caused by the hypoxic microenvironment that is characteristic of the SVZ of the 3 rd ventricle, as we hypothesized in our previous study [ 8 ]. Such up-regulation might trigger the majority of the identified transcriptomic changes (Table 1 ), while enabling tumor formation in the motor cortex and cerebellum ( Supplementary Figure 1 ) - two locations where the injected RG cells did not show any sign of tumorigenic transformation [ 7 ]. Further study will be conducted to investigate whether alterations in these epigenetic regulators are also observed in PNET clinical specimens.…”

“…Recently, we described an animal model of CNS-PNET that was generated by orthotopic transplantation of human Radial Glial (RG) cells - the progenitor cells for adult NSCs - into NOD-SCID mice sub-ventricular zone of the brain [ 7 ], and proposed that BTICs may play a role in the maintenance of these tumors [ 8 ]. We documented expression of RG-BTIC markers such as SOX2, Vimentin and Nestin, BTIC marker OCT3/4, up-regulation of onco-protein cMyc, along with an aberrant accumulation of stabilized tumor-suppressor protein p53 in the model tumors [ 8 ].…”

The constitutively active PKG II mutant effectively inhibits gastric cancer development via a blockade of EGF/EGFR-associated signalling cascades

“…Formalin-fixed paraffin-embedded tumour tissue was used for immunohistochemical analysis, as described previously. 19 The immunohistochemical panel comprised the following antibodies targeting the following proteins: proliferating cell nuclear antigen (PCNA) and matrix metalloproteinase 2/7 (MMP-2/7).…”

Protein Kinases Type II (PKG II) Combined with L-Arginine Significantly Ameliorated Xenograft Tumor Development: Is L-Arginine a Potential Alternative in PKG II Activation?

“…Formalin-fixed paraffin-embedded tumor tissue was used for immunohistochemical analysis following a previously published method [ 20 ].The antibody against PCNA was obtained from Santa Cruz (Dallas, TX, USA).…”