Establishment of primary human meningiomas as subcutaneous xenografts in 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.

Patient-derived xenograft models for the study of benign human neoplasms

Preclinical models are a core feature of translational research, and patient-derived xenograft (PDX) models have increasingly been used with such purpose. PDX involves the transplantation of fresh human tumor samples into immunodeficient mice to overcome immunologic rejection. It is a valuable tool for basic as well as preclinical research, contributing to the establishment of models to characterize the neoplasms to drug screening and to allow the identification of therapeutic targets. The use of these models is justified because they retain the histological and genomic features of the primary tumor. PDX models are well described for malignant neoplasms, for which the advantages are clear and include the development of drug treatments. The establishment of malignant tumors PDX is undeniably important from a medical perspective. However, few studies have used such models for benign neoplasms. The use of PDX for benign neoplasm studies can help to clarify the pathobiology of these diseases, as well as invasion and malignant transformation mechanisms, which from a biological perspective is equally important to the study of malignant tumors. Therefore, the aim of this study is to review the current methodology for PDX model generation and to cover its main applications, focusing on benign neoplasms.

Characterization and comparison of genomic profiles between primary cancer cell lines and parent atypical meningioma tumors

Background

Meningiomas are the second most common primary tumors of the central nervous system. However, there is a paucity of data on meningioma biology due to the lack of suitable preclinical in vitro and in vivo models. In this study, we report the establishment and characterization of patient-derived, spontaneously immortalized cancer cell lines derived from World Health Organization (WHO) grade I and atypical WHO grade II meningiomas.

Methods

We evaluated high-resolution 3T MRI neuroimaging findings in meningioma patients which were followed by histological analysis. RT-qPCR and immunostaining analyses were performed to determine the expression levels of meningioma-related factors. Additionally, flow cytometry and sorting assays were conducted to investigate and isolate the CD133 and CD44 positive cells from primary atypical meningioma cells. Further, we compared the gene expression profiles of meningiomas and cell lines derived from them by performing whole-exome sequencing of the blood and tumor samples from the patients, and the primary cancer cell lines established from the meningioma tumor.

Results

Our results were consistent with earlier studies that reported mutations in NF2, SMO, and AKT1 genes in atypical meningiomas, and we also observed mutations in MYBL2, a gene that was recently discovered. Significantly, the genomic signature was consistent between the atypical meningioma cancer cell lines and the tumor and blood samples from the patient.

Conclusion

Our results lead us to conclude that established meningioma cell lines with a genomic signature identical to tumors might be a valuable tool for understanding meningioma tumor biology, and for screening therapeutic agents to treat recurrent meningiomas.

[Primary culture of human malignant meningioma cells and its intracranial orthotopic transplantation in nude mice]

OBJECTIVE

To obtain stable primary cultures of human malignant meningioma cells and establish an intracranial in-situ tumor model in nude mice.

METHODS

Ten surgical specimens of highly suspected malignant meningioma were obtained with postoperative pathological confirmation. Primary malignant meningioma cells were cultured from the tissues using a modified method and passaged. After identification with cell immunofluorescence, the cultured cells were inoculated into the right parietal lobe of 6 nude mice using stereotaxic apparatus and also transplanted subcutaneously in another 6 nude mice. The nude mice were executed after 6 weeks, and HE staining and immunohistochmistry were used to detect tumor growth and the invasion of the adjacent brain tissues.

RESULTS

The primary malignant meningioma cells were cultured successfully, and postoperative pathology reported anaplastic malignant meningioma. Cell immunofluorescence revealed positivity for vimentin and EMA in the cells, which showed a S-shaped growth curve in culture. Flow cytometry revealed a cell percentage in the Q3 area of (95.99∓2.58)%. Six weeks after transplantation, tumor nodules occurred in the subcutaneous tumor group, and the nude mice bearing the in situ tumor showed obvious body weight loss. The xenografts in both groups contained a mean of (36∓5.35)% cells expressing Ki-67, and the intracranial in situ tumor showed obvious invasion of the adjacent peripheral brain tissues.

CONCLUSION

We obtained stable primary cultures of malignant meningioma cells and successfully established a nude mouse model bearing in situ human malignant meningioma.

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

Although surgical resection of benign human meningiomas is the primary goal, in case of relapse or when they are not fully resectable, other strategies including chemotherapeutical treatment would be appropriate. The initial evaluation of chemotherapeutical agents requires an appropriate tumor model, where the natural characteristics of the original benign tumor is reflected. We here tested, whether primary cell cultures of benign human meningiomas would reliably grow after intracranial transplantation into mice, and whether they would show histomorphological and immunohistochemical characteristics of the original human tumor. Cells of 11 benign human meningiomas were transplanted into the prefrontal cortex of nude mice. After 3 months, the mice were sacrificed and their brains were histologically processed for morphological characterization and measurement of tumor volume. Additionally, the proliferation index (PI), the microvessel density, and epithelial membrane antigen (EMA) were compared between human meningiomas and tumors grown in mice by using immunohistochemical methods. Further, cyclooxygenase-2 (COX-2) expression, a possible target for pharmacological manipulation, was examined. The results showed in almost all mice (93%) a tumor formation with meningothelial histomorphology comparable to the original human tumors. The PI, vascular density and COX-2 expression were similar between human and mice meningiomas, but EMA expression was reduced in mice (P<0.01). In conclusion an implantation of benign human meningioma primary cell cultures in mice reliably results in tumor formation with morphological and immunohistological features comparable to the original human tumor. This model may therefore be suitable to test novel therapeutic agents.

Experimental study on the inhibitory effects of verapamil on the proliferation of meningiomas cells

In order to investigate the effects of verapamil on the proliferation of meningiomas cells in vitro and in vivo, the cultured meningiomas cells were cultured with verapamil at different concentrations for 24 h and the inhibitory effects of verapamil on cell proliferation were observed by MTT method. The meningiomas model was established by implanting the newly removed tumor fragments into the nude mice subcutaneously. The nude mice with tumors were divided into two groups: verapamil-treated group and control group. Tumor volumes were measured and after 12 weeks the tumors were taken out and examined histologically. The expression of proliferating cell nuclear antigen (PCNA) in the tumors was detected by using immunohistochemistry. It was found that verapamil could inhibit the growth of cultured meningiomas cells in a concentration-dependant manner. The inhibitory effect could be observed in the concentration of 1 micromol/L verapamil and the most obvious effects appeared in the concentration of 100 micromol/L. Tumor volume in the verapamiltreated group was obviously smaller than that in the control group (211.40+/-5.50 vs 163.94+/-3.62, P<0.01) and the expression of PCNA was also lower (1.52+/-0.24 vs 2.86+/-0.53, P<0.05). Tumor inhibition rate was about 22.45%. It was suggested that verapamil could inhibit the proliferation and growth of meningiomas cells in vitro and in vivo.

N-ethyl-N-nitrosourea (ENU)-induced meningiomatosis and meningioma in p16(INK4a)/p19(ARF) tumor suppressor gene-deficient mice

The cyclin-dependent kinase (CDK) inhibitor p16(INK4a) and the MDM2 ubiquitin ligase inhibitor p19(ARF) are critical to the regulation of cell cycle progression. Their loss by deletion, mutation or epigenetic silencing is a common molecular alteration in many human cancers. To investigate the role of p16(INK4a)/p19(ARF) deficiency in CNS tumor pathogenesis, pregnant mice bearing p16(-/-)/p19(-/-), p16(+/-)/p19(+/-), and p16(+/+)/p19(+/+) embryos were exposed transplacentally on gestation day 14 to a single dose of the potent carcinogen, ethylnitrosourea (ENU). p16(+/-)/p19(+/-) male mice treated with ENU developed meningial proliferative lesions with a high incidence (5/10). The incidence was lower in other ENU-treated animals of both sexes and none occurred in saline-treated control animals. The lesions ranged from widespread meningeal proliferation and plaque-like thickening by neoplastic spindle cells consistent with meningiomatosis to a larger discrete mass consistent with a meningioma. Ultrastructural analysis revealed the presence of intercellular junctions between cells, supporting a meningothelial histogenesis. Spontaneous meningiomas occur rarely in wild-type mice but are a common neoplasm afflicting humans, accounting for between 13 and 26% of primary intracranial neoplasms. This ENU inducible meningeal lesion in p16(+/-)/p19(+/-) mice may provide additional insight into the pathogenesis of meningeal neoplasia and aid the development of therapeutics.

Establishment of an in vivo meningioma model with human telomerase reverse transcriptase

OBJECTIVE

The lack of meningioma models has hindered research on the pathogenesis and treatment of this commonly diagnosed primary brain tumor. Animal models of meningioma have been difficult to develop, especially those derived from Grade I tumors, which display very slow growth rates, senesce at early passages, and infrequently survive as explants in vivo. In this study, the authors report the establishment of two benign immortalized meningioma cell lines, Me10T and Me3TSC, that can serve as useful models of human meningioma.

METHODS

Tissue specimens obtained at the time of surgery were cultured in vitro and transduced with human telomerase reverse transcriptase/SV40 large T antigen to establish long-term cell lines. The telomeric activity, growth kinetics, immunophenotype, and karyotyping of the cell lines were investigated. The growth inhibitory effects of the antitumor therapies, hydroxyurea and sodium butyrate, on these cell lines were determined. In addition, immortalized cell lines were implanted subdurally into mice to confirm their ability to form tumors.

RESULTS

Two immortalized benign meningioma cell lines, Me10T and Me3TSC, transduced with catalytic subunit human telomerase reverse transcriptase alone or human telomerase reverse transcriptase and SV40 large T antigen, were established. The meningeal phenotype of the established cell cultures and orthotopic xenografts was confirmed by immunostaining. After subdural injection into athymic nude mice, both cell lines formed identifiable tumors with histological features and immunostaining patterns of human meningioma.

CONCLUSION

The Me3TSC and Me10T cell lines can serve as useful model systems for biological studies and the evaluation of novel therapies on meningioma.