Comparative morphological and immunohistochemical study of human meningioma after intracranial transplantation into nude mice

Meningioma animal models: a systematic review and meta-analysis

BACKGROUND

Animal models are widely used to study pathological processes and drug (side) effects in a controlled environment. There is a wide variety of methods available for establishing animal models depending on the research question. Commonly used methods in tumor research include xenografting cells (established/commercially available or primary patient-derived) or whole tumor pieces either orthotopically or heterotopically and the more recent genetically engineered models-each type with their own advantages and disadvantages. The current systematic review aimed to investigate the meningioma model types used, perform a meta-analysis on tumor take rate (TTR), and perform critical appraisal of the included studies. The study also aimed to assess reproducibility, reliability, means of validation and verification of models, alongside pros and cons and uses of the model types.

METHODS

We searched Medline, Embase, and Web of Science for all in vivo meningioma models. The primary outcome was tumor take rate. Meta-analysis was performed on tumor take rate followed by subgroup analyses on the number of cells and duration of incubation. The validity of the tumor models was assessed qualitatively. We performed critical appraisal of the methodological quality and quality of reporting for all included studies.

RESULTS

We included 114 unique records (78 using established cell line models (ECLM), 21 using primary patient-derived tumor models (PTM), 10 using genetically engineered models (GEM), and 11 using uncategorized models). TTRs for ECLM were 94% (95% CI 92-96) for orthotopic and 95% (93-96) for heterotopic. PTM showed lower TTRs [orthotopic 53% (33-72) and heterotopic 82% (73-89)] and finally GEM revealed a TTR of 34% (26-43).

CONCLUSION

This systematic review shows high consistent TTRs in established cell line models and varying TTRs in primary patient-derived models and genetically engineered models. However, we identified several issues regarding the quality of reporting and the methodological approach that reduce the validity, transparency, and reproducibility of studies and suggest a high risk of publication bias. Finally, each tumor model type has specific roles in research based on their advantages (and disadvantages).

SYSTEMATIC REVIEW REGISTRATION

PROSPERO-ID CRD42022308833.

Modeling Meningiomas: Optimizing Treatment Approach

Preclinical meningioma models offer a setting to test molecular mechanisms of tumor development and targeted treatment options but historically have been challenging to generate. Few spontaneous tumor models in rodents have been established, but cell culture and in vivo rodent models have emerged along with artificial intelligence, radiomics, and neural networks to differentiate the clinical heterogeneity of meningiomas. We reviewed 127 studies using PRISMA guideline methodology, including laboratory and animal studies, that addressed preclinical modeling. Our evaluation identified that meningioma preclinical models provide valuable molecular insight into disease progression and effective chemotherapeutic and radiation approaches for specific tumor types.

Novel Medical Therapies in Meningiomas

Meningiomas are the most common primary brain tumor in adults and have been historically managed with surgery and radiation therapy. However, in patients with inoperable, recurrent or high-grade tumors, medical therapy is often needed. Traditional chemotherapy and hormone therapy have been largely ineffective. However, with improved understanding of the molecular drivers in meningioma, there has been increasing interest in targeted molecular and immune therapies. In this chapter, we will discuss recent advances in meningioma genetics and biology and review current clinical trials with targeted molecular treatment and other novel therapies.

Tumor-Derived Cell Culture Model for the Investigation of Meningioma Biology

Meningioma is the most common primary central nervous system tumor. Although mostly nonmalignant, meningioma can cause serious complications by mass effect and vasogenic edema. While surgery and radiation improve outcomes, not all cases can be treated due to eloquent location. Presently no medical treatment is available to slow meningioma growth owing to incomplete understanding of the underlying pathology, which in turn is due to the lack of high-fidelity tissue culture and animal models. We propose a simple and rapid method for the establishment of meningioma tumor-derived primary cultures. These cells can be maintained in culture for a limited time in serum-free media as spheres and form adherent cultures in the presence of 4% fetal calf serum. Many of the tissue samples show expression of the lineage marker PDG2S, which is typically retained in matched cultured cells, suggesting the presence of cells of arachnoid origin. Furthermore, nonarachnoid cells including vascular endothelial cells are also present in the cultures in addition to arachnoid cells, potentially providing a more accurate tumor cell microenvironment, and thus making the model more relevant for meningioma research and high-throughput drug screening.

Mouse Models in Meningioma Research: A Systematic Review

Meningiomas are the most frequent primitive central nervous system tumors found in adults. Mouse models of cancer have been instrumental in understanding disease mechanisms and establishing preclinical drug testing. Various mouse models of meningioma have been developed over time, evolving in light of new discoveries in our comprehension of meningioma biology and with improvements in genetic engineering techniques. We reviewed all mouse models of meningioma described in the literature, including xenograft models (orthotopic or heterotopic) with human cell lines or patient derived tumors, and genetically engineered mouse models (GEMMs). Xenograft models provided useful tools for preclinical testing of a huge range of innovative drugs and therapeutic options, which are summarized in this review. GEMMs offer the possibility of mimicking human meningiomas at the histological, anatomical, and genetic level and have been invaluable in enabling tumorigenesis mechanisms, including initiation and progression, to be dissected. Currently, researchers have a range of different mouse models that can be used depending on the scientific question to be answered.

Intracranial rat glioma model for tumor resection and local treatment

BACKGROUND

Although tumor resection is among the most important prognostic factors, high grade gliomas regrow in most cases. Also, resection of glial tumors in eloquent brain regions is not or only partially possible. Despite these severe restraints, however, only a few in-vivo models have been established to investigate tumor recurrence and local treatment. Here we characterize the intracranial BT4Ca rat glioma as a model for these aspects.

NEW METHOD

BT4Ca cells were stereotaxically implanted into the frontal cortex of BDIX rats. Rats were than allocated to (1) a control group, which received no further treatment; (2) a catheter group, where a catheter was implanted for repeated microinjection of vehicle every 3rd day as catheter-control; (3) a resection group, where the tumor was microsurgically removed eight days after cell injection. Postoperatively, survival time, weight and general health condition were scored and the tumor size was histologically assessed.

RESULTS

Injection of BT4Ca cells induced fast-growing tumors with a mean survival time of 16 days in the control and catheter groups. Resection significantly prolonged survival time whereby the tumor regrew in all rats. Tumor size was similar between all groups.

COMPARISON WITH EXISTING METHOD(S)

We here present a robust and reliable intracranial rat glioma model, which is suitable to simulate tumor recurrence after surgical resection and local treatment. Importantly, this model does not require advanced imaging or elaborate surgical techniques.

CONCLUSIONS

The intracranial BT4Ca glioma model appears to be a feasible tool to investigate tumor recurrence after resection and to test local treatment.

Advances in meningioma genetics: novel therapeutic opportunities

Meningiomas currently are among the most frequent intracranial tumours. Although the majority of meningiomas can be cured by surgical resection, ∼20% of patients have an aggressive clinical course with tumour recurrence or progressive disease, resulting in substantial morbidity and increased mortality of affected patients. During the past 3 years, exciting new data have been published that provide insights into the molecular background of meningiomas and link sites of tumour development with characteristic histopathological and molecular features, opening a new road to novel and promising treatment options for aggressive meningiomas. A growing number of the newly discovered recurrent mutations have been linked to a particular clinicopathological phenotype. Moreover, the updated WHO classification of brain tumours published in 2016 has incorporated some of these molecular findings, setting the stage for the improvement of future therapeutic efforts through the integration of essential molecular findings. Finally, an additional potential classification of meningiomas based on methylation profiling has been launched, which provides clues in the assessment of individual risk of meningioma recurrence. All of these developments are creating new prospects for effective molecularly driven diagnosis and therapy of meningiomas.

Pleomorphism and drug resistant cancer stem cells are characteristic of aggressive primary meningioma cell lines

Background

Meningioma tumors arise in arachnoid membranes, and are the most reported central nervous system (CNS) tumors worldwide. Up to 20% of grade I meningioma tumors reoccur and currently predictive cancer stem cells (CSCs) markers for aggressive and drug resistant meningiomas are scarce.

Methods

Meningioma tissues and primary cell lines were investigated using whole transcriptome microarray analysis, immunofluorescence staining of CSCs markers (including CD133, Sox2, Nestin, and Frizzled 9), and drug treatment with cisplatin or etoposide.

Results

Unsupervised hierarchical clustering of six meningioma samples separated tissues into two groups. Analysis identified stem cells related pathways to be differential between the two groups and indicated the de-regulation of the stem cell associated genes Reelin (RELN), Calbindin 1 (CALB1) and Anterior Gradient 2 Homolog (AGR2). Immunofluorescence staining for four tissues confirmed stemness variation in situ. Biological characterization of fifteen meningioma primary cell lines concordantly separated cells into two functionally distinct sub-groups. Pleomorphic cell lines (NG type) grew significantly faster than monomorphic cell lines (G type), had a higher number of cells that express Ki67, and were able to migrate aggressively in vitro. In addition, NG type cell lines had a lower expression of nuclear Caspase-3, and had a significantly higher number of CSCs co-positive for CD133+ Sox2+ or AGR2+ BMI1+. Importantly, these cells were more tolerant to cisplatin and etoposide treatment, showed a lower level of nuclear Caspase-3 in treated cells and harbored drug resistant CSCs.

Conclusion

Collectively, analyses of tissues and primary cell lines revealed stem cell associated genes as potential targets for aggressive and drug resistant meningiomas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-017-0441-7) contains supplementary material, which is available to authorized users.

A new and reliable guide for studies of neuronal loss based on focal lesions and combinations of in vivo and in vitro approaches

In this study, we describe a simple and reliable method to study neuroprotective effects in living and organized neural tissue. This method, which was based on retinal explants for in vivo focal lesions, was conceived as a collection of modular procedures, which can be customized for particular demands. With this model, it is possible to combine immunohistochemistry with image data analysis to track the two- or three-dimensional redistribution of proteins as a time/space function of primary cell loss. At the same time, it is possible to finely control the exposure of the tissue to specific drugs and molecules. In order to illustrate the use of the proposed method, we tested the effects of two different nanotube compounds on retinal explant viability. Transcriptome analyses can be separately performed in the lesion focus and penumbra with laser capture microdissection followed by polymerase chain reaction analyses. In addition, other common experimental drawbacks, such as high individual variance, are eliminated. With intraocular injections, treatments can be verified in vivo, with one eye serving as the experimental tissue and the other serving as the control tissue. In summary, we describe a flexible and easy method, which can be useful in combination with a broad variety of recently developed neuroprotective strategies, to study neurodegeneration.

Effect of systemic celecoxib on human meningioma after intracranial transplantation into nude mice

BACKGROUND

Meningiomas are mostly benign, but they may have a notorious tendency to recur when total resection is not possible. Systemic chemotherapeutical treatment has been largely disappointing. The treatment of meningiomas with the cyclooxygenase-2 (COX-2) inhibitor celecoxib showed inhibitory-growth effects in vitro and in vivo after subcutaneous transplantation into mouse. So far, celecoxib has never been tested in an orthotopic model of meningioma. In this work, we tested the effects of celecoxib on the growth of human benign meningiomas after transplantation into the prefrontal cortex of nude mice after confirming the inhibitory in vitro effect on these cells.

METHODS

Primary cell cultures were stereotactically implanted into mice and were treated with 0, 750, or 1,500 ppm celecoxib for 3 months. The mice were then killed and blood was analyzed for celecoxib concentration. The mice brains were histologically processed for measurement of tumor volume, COX-2 expression, proliferation index (PI), intratumoral microvessel density (iMVD), and vascular endothelial growth factor (VEGF) expression.

RESULTS

Treatment with celecoxib had no effect on tumor volume, despite the fact that we found a dose-dependent inhibitory effect on cell cultures and there was a sufficiently high celecoxib concentration in blood plasma and brain tissue. Additionally, celecoxib had neither an effect on COX-2 and VEGF expression nor on the PI and iMVD.

CONCLUSIONS

Our findings suggest that celecoxib may not be effective on meningioma growth in clinical settings. In general, these results may indicate that the effect of treatment on brain tumors should not only be tested in a heterotopic environment but also in the orthotopic location of these tumors.