Possible involvement of brain tumour stem cells in the emergence of a fast-growing malignant meningioma after surgical resection and radiotherapy of high-grade astrocytoma: case report and preliminary laboratory investigation

Meningioma Tumor Microenvironment

The tumor microenvironment consists of noncancerous cells, such as immune cells and fibroblasts, and the proteins produced by these cells as well as the extracellular matrix components in the environment around a tumor. Tumor influences the behavior of the cells present in the surrounding environment, while the cells in the tumor microenvironment modulate the evolution of the tumor. Little is known about the microenvironment of meningioma, the most common benign intracranial tumor. Here, we review the current knowledge of the tumor microenvironment of meningioma and discusses its importance in meningioma tumorigenesis as well as in the designation of novel therapeutic approaches.

Expression of Components of the Renin-Angiotensin System by the Putative Stem Cell Population Within WHO Grade I Meningioma

Aim: We have recently demonstrated a putative stem cell population within WHO grade I meningioma (MG) that expressed embryonic stem cell (ESC) markers OCT4, NANOG, SOX2, KLF4 and c-MYC, localized to the endothelial and pericyte layers of the microvessels. There is increasing recognition that the renin-angiotensin system (RAS) plays a critical role in stem cell biology and tumorigenesis. This study investigated the expression of components of the RAS: pro-renin receptor (PRR), angiotensin converting enzyme (ACE), angiotensin II receptor 1 (ATIIR1), and angiotensin II receptor 2 (ATIIR2) on the putative stem cell population on the microvessels of WHO grade I MG.

Methods: 3,3-Diaminobenzidine (DAB) immunohistochemical (IHC) staining was performed on WHO grade I MG tissue samples from 11 patients for PRR, ACE, ATIIR1, and ATIIR2. Two of the MG samples subjected to DAB IHC staining underwent immunofluorescence (IF) IHC staining to investigate co-expression of each of these components of the RAS in using combinations of CD34 and ESC marker SOX2 or OCT4. NanoString mRNA expression analysis and Western blotting (WB), were performed on six snap-frozen MG tissue samples to confirm mRNA and protein expression of these proteins, respectively.

Results: DAB IHC staining demonstrated expression of PRR, ACE, ATIIR1, and ATIIR2 within all 11 MG tissue samples. WB and NanoString mRNA analyses, confirmed protein and mRNA expression of these proteins, respectively. IF IHC staining showed PRR, ATIIR1 and ATIIR2 were localized to the OCT4⁺ and SOX2⁺ endothelium and the pericyte layer of MG while ACE was localized to the OCT4⁺ endothelium of the microvesels.

Conclusion: The novel finding of the expression of PRR, ACE, ATIIR1, and ATIIR2 on the putative stem cell population on the microvessels of WHO grade I MG, suggests that these stem cells may be a potential therapeutic target by manipulation of the RAS.

Expression of Embryonic Stem Cell Markers on the Microvessels of WHO Grade I Meningioma

Aim: The presence of cells within meningioma (MG) that express embryonic stem cell (ESC) markers has been previously reported. However, the precise location of these cells has yet to be determined.

Methods: 3,3-Diaminobenzidine (DAB) immunohistochemical (IHC) staining was performed on 11 WHO grade I MG tissue samples for the expression of the ESC markers OCT4, NANOG, SOX2, KLF4 and c-MYC. Immunofluorescence (IF) IHC staining was performed to investigate the localization of each of these ESC markers. NanoString and colorimetric in situ hybridization (CISH) mRNA expression analyses were performed on six snap-frozen MG tissue samples to confirm transcriptional activation of these proteins, respectively.

Results: DAB IHC staining demonstrated expression of OCT4, NANOG, SOX2, KLF4, and c-MYC within all 11 MG tissue samples. IF IHC staining demonstrated the expression of the ESC markers OCT4, NANOG, SOX2, KLF4, and c-MYC on both the endothelial and pericyte layers of the microvessels. NanoString and CISH mRNA analyses confirmed transcription activation of these ESC markers.

Conclusion: This novel finding of the expression of all aforementioned ESC markers in WHO grade I MG infers the presence of a putative stem cells population which may give rise to MG.

Tumour stem cells in meningioma: A review

Meningioma is a common intracranial and intraspinal neoplasm accounting for 25-30% of all primary neurological tumours. It is associated with high rates of recurrence especially in higher-grade tumours and lesions located at the skull base. Cancer stem cells are increasingly recognised as the origin of cancer and are attributed to loco-regional recurrence, metastasis and treatment resistance. This review presents the accumulating evidence of the presence of tumour stem cells within meningioma and the stem cell markers being used to characterise this putative primitive population within this common tumour.

Identification of new HLA-A*0201-restricted cytotoxic T lymphocyte epitopes from neuritin

Identification of cytotoxic T lymphocyte (CTL) epitopes from additional tumor antigens is essential for the development of specific immunotherapy of malignant tumors. Neuritin, a recently discovered antigen overexpressed in astrocytoma, is considered to be a promising target for biological therapy. In the present study, we predicted and identified HLA-A2-restricted CTL epitopes from neuritin by using the following four-step procedure: (1) computer-based epitope prediction from the amino acid sequence of neuritin; (2) peptide-binding assay to determine the affinity of the predicted peptide with HLA-A2.1 molecule; (3) stimulation of primary T cell response against the predicted peptides in vitro; and (4) testing of the induced CTLs toward target cells expressing neuritin and HLA-A2.1. The results demonstrated that effectors induced by peptides of neuritin containing residues 13-21, 121-129 and 4-12 could specifically-secrete interferon-γ and lyse target cells. Our results indicate that these peptides are new HLA-A2.1-restricted CTL epitopes, and may serve as valuable tools for astrocytoma immunotherapy.

Radiation-induced meningiomas after high-dose cranial irradiation

Radiation-induced meningiomas (RIM) are known to occur after high and low dose cranial radiation therapy. Currently, RIM are the most common form of radiation-induced neoplasm reported. We present the largest series of RIM induced by high dose radiation reported thus far and review the literature. Radiation therapy was most commonly given for childhood malignancy. We compared our group of 26 patients with RIM with previously published reports of RIM, and also with 364 patients with spontaneous meningioma (SM) treated at The Royal Melbourne Hospital between 2007 and 2011 with regard to age, gender, and histopathology. In our group of patients with RIM, the mean age at presentation was 38.5 years, in comparison to 60.1 years for patients with SM. The female-to-male ratio was 1.88:1 in RIM compared to 2.37:1 for SM. Of the RIM, 86.5% were World Health Organization (WHO) grade I and 11.5% were grade II (atypical) meningiomas. There were no anaplastic or malignant RIM. Of the SM, 91.5% were WHO grade I, 7.1% WHO grade II, and 1.4% WHO grade III meningiomas. The characteristics of RIM induced by low dose radiation therapy have been well described. It is timely to consider RIM due to high dose radiation, which is now frequently employed in the management of various childhood and other malignancies.

Evidence of endothelial progenitor cells in the human brain and spinal cord arteriovenous malformations

BACKGROUND

Brain and spinal cord arteriovenous malformations (AVMs) are characterized by aberrant angiogenesis and vascular remodeling. Endothelial progenitor cells (EPCs) can be recruited by stromal cell-derived factor-1 (SDF-1), and participate in vascular remodeling in both physiological and pathological settings.

OBJECTIVE

To investigate whether there are increased EPC levels in the brain and spinal cord AVM nidus.

METHODS

Microsurgical specimens without endovascular embolization and radiosurgery from the brain (n = 12) and spinal cord (n = 5) AVMs were examined. Hemangioblastoma, meningioma, cerebral cortex obtained from epilepsy surgery, and the basilar artery from the autopsy were chosen for control comparisons. EPCs were identified as cells that were double-positive for the stem cell marker CD133 and the endothelial cell marker VEGFR-2 (vascular endothelial growth factor receptor-2 or KDR). In addition, SDF-1 was characterized by immunohistochemistry.

RESULTS

Both brain and spinal AVM tissues displayed more CD133-, SDF-1-, and CD68-positive signals than epilepsy and basilar artery control tissues. The level of EPCs was increased in the brain and spinal cord AVM nidus, mainly at the edge of the vessel wall. The expression of SDF-1 was colocalized with CD31-positive and α-smooth muscle cells, and was predominantly found within the vessel wall.

CONCLUSION

Our data demonstrate that EPCs are present in the nidus of the brain and spinal cord AVMs, which may mediate pathological vascular remodeling and impact the clinical course of AVMs.

Distribution of lysosome-associated membrane proteins-1 and -2, and cathepsin D in eosinophilic granular bodies: possible relationship to cyst development in pilocytic astrocytomas

Pilocytic astrocytomas are usually cystic; cyst formation within these tumours may result in increased intracranial pressure, due to the effect of their mass, and contribute to cerebral damage. Eosinophilic granular bodies (EGBs) are produced abundantly in pilocytic astrocytomas but their role in disease progression remains unknown. Immunohistochemistry studies showed EGBs to exhibit pronounced reactivity to antibodies against lysosome-associated membrane proteins (LAMP)-1 and LAMP-2, and the lysosomal enzyme cathepsin D. Both LAMP-1 and LAMP-2 showed peripheral rim and granular staining patterns. The EGBs were scattered widely across cysts and, where EGBs aggregated in clusters, were usually close to areas of fluid in the cysts. Most EGBs had nuclei either attached or close by, indicating that the EGBs may be derived from anucleated astrocytes. The results suggest that EGBs, together with other factors, may play a role in the development of cysts in pilocytic astrocytomas.