TB-2 Patient-derived meningioma organoid model demonstrates FOXM1 dependent tumor proliferation

Recent comprehensive studies have revealed several molecular alterations that are frequently found in meningiomas. However, effective treatment reagents targeting specific molecular alterations have not yet been identified because of the limited number of representative research models of meningiomas. We established 18 organoid models comprising of two malignant meningioma cells (HKBMM and IOMM-Lee), 10 benign meningiomas, four malignant meningiomas, and two solitary fibrous tumors (SFTs). Using immunohistochemistry and molecular analyses consisting of whole exome sequencing, RNA-seq, and DNA methylation analyses, we compared the histological findings and molecular profiling of organoid models with those of parental tumors. The organoids exhibited consistent histological features and molecular profiles with those of the parental tumors. Using a public database of meningioma, we identified that upregulated forkhead box M1 (FOXM1) was correlated with increased tumor proliferation. Overexpression of FOXM1 in benign meningioma organoids increased organoid proliferation; depletion of FOXM1 in malignant organoids decreased proliferation. Additionally, thiostrepton, a FOXM1 inhibitor combined with radiation therapy, significantly inhibited proliferation of malignant meningioma organoid models (P<0.01). An organoid model for meningioma enabled us to elucidate the tumor biology of meningioma along with potent treatment targets for meningioma.

ET-6 Gemcitabine radiosensitization primes irradiated malignant meningioma cells for senolytic elimination by navitoclax

BACKGROUND: Malignant meningioma is an aggressive tumor that requires adjuvant radiotherapy after surgery, yet there has been no standard systemic therapy established so far. We have demonstrated that malignant meningioma cells are exquisitely sensitive to gemcitabine due to their increased expression of hENT1 and dCK, which play critical roles in the intracellular transport and activation of gemcitabine, respectively (Takeda et al. Oncotarget 8:90996, 2017; Yamamoto et al., Neuro-Oncol 23:945, 2021). Significantly, in support of our findings, the efficacy and safety of gemcitabine have recently been documented in a small case series of patients with recurrent meningiomas, which has further led to a phase 2 clinical trial to evaluate the efficacy of gemcitabine in recurrent high-grade meningiomas (Khaddar et al., South Asian J Cancer 9:261, 2020). Besides its efficacy as a single agent, gemcitabine reportedly has a radiosensitizing effect in pancreatic cancer. However, it remains unknown whether or how gemcitabine interacts with ionizing radiation (IR) in malignant meningioma cells. METHODS: We examined radiosensitization effects of gemcitabine using malignant meningioma cell lines and xenografts (s.c. and i.c.) and explored the underlying mechanisms. RESULTS: Gemcitabine sensitized malignant meningioma cells remarkably to IR through the induction of senescence both in vitro and in vivo. Gemcitabine augmented the intracellular production of reactive oxygen species (ROS) by IR, which, together with cell growth suppression/senescence induced by this combination, was inhibited by N-acetyl-cysteine, suggesting a pivotal role for ROS in these combinatorial effects. Navitoclax, a senolytic drug, further enhanced the effects of the combination of gemcitabine and IR in vitro and in vivo by strongly inducing apoptotic cell death in senescent cells. CONCLUSION: These results suggest that gemcitabine is not only a promising radiosensitizer for malignant meningioma but also creates in combination with IR a therapeutic vulnerability of senescent meningioma cells to senolytics. (submitted for publication)

INNV-23. CASE REPORT OF CISPLATIN + ETOPOSIDE FOR THE TREATMENT OF METASTATIC MALIGNANT MENINGIOMA

INTRODUCTION Meningioma have an annual incidence of 5 per 100,000 and is the most frequent primary tumor of the central nervous system. Risk factors include radiotherapy and hormone intake. Most meningioma are grade I benign tumors, but up to 15% are atypical and 2% anaplastic according to the WHO 2016 histological criteria. Extra-CNS metastasis is exceedingly rare but carry a poor prognosis. Surgical resection and radiation therapy are the only approved therapies for the treatment of high grade or recurrent meningioma. Chemotherapy options have been limited and none have shown significant response rates. METHODS We report a case of a 33 year old male with an anaplastic meningioma (WHO Grade III) with metastasis to the lungs and rapid progression despite repeat resection. The subject was previously treated with resection and radiation therapy to a skull base/sinonasal lesion. Progression occurred at anterior cranial fossa, which required repeat resection. Within a month, the meningioma showed substantial progression with invasion into the orbit and nasopharynx as well as metastasis to the lung. The subject experienced significant clinical decline which included bilateral vision loss. The subject was treated with Cisplatin and Etoposide for 4 cycles. RESULTS The patient had immediate clinical improvement after the first cycle. Repeat MRI imaging of the brain showed partial response with approximately 40% tumor reduction, and CT of the chest showed complete response. The subject’s performance status also improved significantly with treatment including recovery of eyesight bilaterally. CONCLUSION This case showed that the use of Cisplatin + Etoposide for metastatic malignant meningioma can have significant objective and clinical response. The use of this regimen warrants further investigation. A clinical trial is currently being developed.

EXTH-54. PHOTODYNAMIC ONCOLYTIC VIROTHERAPY INCORPORATING GENETICALLY ENGINEERED PHOTOSENSITIZER KILLERRED FOR THE TREATMENT OF CENTRAL NERVOUS SYSTEM MALIGNANCIES

BACKGROUND Photodynamic therapy (PDT) is a targeted cancer therapy utilizing tumor-specific accumulation of photosensitizers and generation of reactive oxygen species (ROS) upon receiving specific light. The deadly CNS malignancies, high-grade gliomas and malignant meningioma, represent excellent candidates for this therapeutic method due to accessibility to light irradiation at the time of surgery. On the other hand, oncolytic virotherapy using a genetically engineered oncolytic herpes simplex virus (oHSV), has been intensively investigated as a multi-mechanistic therapy against these tumors. One of the advantages of oHSV is its ability to incorporate therapeutic transgenes. Our study aims to address our hypothesis that incorporating KillerRed, the first fully genetically encoded photosensitizing fluorescent protein, into oHSV will establish photodynamic oncolytic virotherapy that enhances tumoricidal efficacy as a novel treatment approach to CNS neoplasms. METHOD The optical properties of the intracellular KillerRed protein expressed in cells were determined by scanning by a multi-mode microplate reader to determine the optimal irradiation wavelength. In vitro efficacy of KillerRed-mediated PDT was tested using human glioblastoma and malignant meningioma cell lines. oHSV G47delta expressing KillerRed was constructed by a bacterial artificial chromosome-based method. KillerRed-transduced cells were confirmed to express red fluorescence, followed by irradiation by an amber color LED. Cell death and viability were assessed by DAPI staining and MTS assay, respectively. ROS generation post light treatment was assessed by DCF-DA cellular ROS assay. RESULTS KillerRed had an excitation peak at 580-585nm in transduced cells. Light irradiation by an amber LED after infection with G47delta-KillerRed induced increased cell growth inhibition and death compared with virus infection without light or light alone. Increased ROS production was observed following KillerRed PDT. CONCLUSION G47delta-KillerRed enables a combination of oncolytic virus therapy and PDT to augment tumor killing. This approach is being tested in in vivo mouse models using potent focused laser irradiation.

Gemcitabine radiosensitization primes irradiated malignant meningioma cells for senolytic elimination by navitoclax

Background Malignant meningioma is an aggressive tumor that requires adjuvant radiotherapy after surgery, yet there has been no standard systemic therapy established so far. We recently reported that malignant meningioma cells are highly sensitive to gemcitabine; however, it remains unknown whether or how gemcitabine interacts with ionizing radiation (IR) in malignant meningioma cells. Methods We examined radiosensitization effects of gemcitabine using malignant meningioma cell lines and xenografts and explored the underlying mechanisms. Results Gemcitabine sensitized malignant meningioma cells to IR through the induction of senescence both in vitro and in vivo. Gemcitabine augmented the intracellular production of reactive oxygen species (ROS) by IR, which, together with cell growth suppression/senescence induced by this combination, was inhibited by N-acetyl-cysteine, suggesting a pivotal role for ROS in these combinatorial effects. Navitoclax, a senolytic drug that inhibits Bcl-2 proteins, further enhanced the effects of the combination of gemcitabine and IR by strongly inducing apoptotic cell death in senescent cells. Conclusion These results not only indicate the potential of gemcitabine as a candidate radiosensitizer for malignant meningioma, but also reveal a novel role for gemcitabine radiosensitization as a means to create a therapeutic vulnerability of senescent meningioma cells to senolytics.

P04.05 Targeted Gene-Expression analysis during malignant transformation in primary and secondary malignant meningioma

BACKGROUND Malignant meningiomas comprise 2–5% of all meningiomas. The process of malignant transformation when benign meningiomas (WHO grade I-II) become malignant (WHO grade III) has not previously been investigated in sequential tumour surgeries. Upregulation of FOXM1 expression and DREAM-complex repression have shown phenotypical subgroups correlating with WHO grade and aggressiveness. We investigated the RNA expression of 30 genes central to meningioma biology and 770 genes involved in neuroinflammatory pathways in primary and secondary malignant meningioma patients who underwent one to several operations. MATERIALS AND METHODS We identified a cohort of consecutive malignant meningioma patients treated at Rigshospitalet, Copenhagen from 2000–2020 (n=51) and gathered their malignant tumours and previous WHO grade I/II tumours. The malignant cohort (MC) was counter matched with a benign cohort (BC) where patients had no recurrences during follow-up. RNA expression signatures from 140 samples from the MC and 51 samples from the BC were analysed with the Nanostring Neuroinflammation panel customized with 30 genes known to be relevant in meningioma phenotypes. RESULTS 49% of MC patients had a previous grade I/II meningioma making them secondary malignant meningioma patients. Progression-free survival calculated from first malignant surgery to first recurrence or death showed no significant difference in the primary vs. secondary patients. Preliminary results of single-gene analysis of MC tumours showed FOXM1, MYBL2, TOP2A, BIRC5 expression was higher in WHO grade III samples. Gene-expression signatures in the individual patients and gene ontology enrichment analyses are in process. CONCLUSIONS FOXM1, MYBL2, TOP2A, BIRC5 RNA expression levels seem to rise during malignant progression across patients. Gene-expression analysis using the Nanostring technology is feasible and a potentially powerful tool to distinguish meningiomas prone to malignant transformation from truly benign meningiomas.

Curcumin Inhibits HGF-Induced EMT by Regulating c-MET-Dependent PI3K/Akt/mTOR Signaling Pathways in Meningioma

Meningiomas, which are the most common primary intracranial tumors, have highly aggressive cells in malignant cases. Due to its extensive antitumor effects, curcumin is widely used in experimental and clinical studies. However, the role of curcumin during the epithelial-mesenchymal transition (EMT) in meningioma has not been established. We found that curcumin blocks hepatocyte growth factor- (HGF-) induced proliferation, migration, invasion, and EMT of human malignant meningioma cells by regulating the PI3K/Akt/mTOR signaling pathway. In addition, treatment of human malignant meningioma cells with the tyrosine protein kinase (c-MET) inhibitor (SU11274) or the phosphoinositide 3-kinase (PI3K) inhibitor (LY294002) suppressed HGF-induced migration and EMT. Furthermore, we found that curcumin inhibited tumor growth and HGF-induced EMT in mice subjected to subcutaneous xenotransplantation. These findings indicate that HGF regulates EMT in human malignant meningioma cells through c-MET/PI3K/Akt/mTOR modulation. In conclusion, curcumin inhibits HGF-induced EMT by targeting c-MET and subsequently blocking the PI3K/Akt/mTOR pathway.

OTEH-3. Targeted Gene-Expression analysis during malignant transformation in primary and secondary malignant meningioma

Background Malignant meningiomas comprise 2–5% of all meningiomas. The process of malignant transformation when benign meningiomas (WHO grade I-II) become malignant (WHO grade III) has not previously been investigated in sequential tumour surgeries. Upregulation of FOXM1 expression and DREAM-complex repression have shown phenotypical subgroups correlating with WHO grade and aggressiveness. We investigated the RNA expression of 30 genes central to meningioma biology and 770 genes involved in neuroinflammatory pathways in primary and secondary malignant meningioma patients who underwent one to several operations. Methods We identified a cohort of consecutive malignant meningioma patients treated at Rigshospitalet, Copenhagen from 2000–2020 (n=51) and gathered their malignant tumours and previous WHO grade I/II tumours. The malignant cohort (MC) was counter matched with a benign cohort (BC) where patients had no recurrences during follow-up. RNA expression signatures from 140 samples from the MC and 51 samples from the BC were analysed with the Nanostring Neuroinflammation panel customized with 30 genes known to be relevant in meningioma phenotypes. Results 49% of MC patients had a previous grade I/II meningioma making them secondary malignant meningioma patients. Progression-free survival calculated from first malignant surgery to first recurrence or death showed no significant difference in the primary vs. secondary patients. Preliminary results of single-gene analysis of MC tumours showed FOXM1, MYBL2, TOP2A, BIRC5 expression was higher in WHO grade III samples. Gene-expression signatures in the individual patients and gene ontology enrichment analyses are in process. Conclusions FOXM1, MYBL2, TOP2A, BIRC5 RNA expression levels seem to rise during malignant progression across patients. Gene-expression analysis using the Nanostring technology is feasible and a potentially powerful tool to distinguish meningiomas prone to malignant transformation from truly benign meningiomas.