The role of chemotherapy and targeted therapy in the treatment of intracranial meningioma

Diarylpentanoid, a curcumin analog, inhibits malignant meningioma growth in both in vitro and in vivo models

BACKGROUND

Malignant meningioma metastasizes systemically, primarily due to its role in epithelial-mesenchymal transition. Although the prognosis is extremely poor, drug development efforts have been limited, because this tumor is categorized as a rare form.

AIM

To examine growth suppressive effect of GO-Y030, a diarylpentanoid curcumin analog, (1E,4E)-1,5-bis [3,5-bis (methoxymethoxy) phenyl] penta-1,4-dien-3-one against the malignant meningioma.

METHODS

The growth suppression of malignant meningioma cells by GO-Y022 and GO-Y030 were examined, using IOMM-Lee and HKBMM cell lines. Male nude mice aged eight weeks, specifically BALB/cSlc-nu/nu mice received a subcutaneous inoculation of IOMM-Lee (10⁷ cells/site) on their back and 30 μg/kg of recombinant hepatocellular growth factor (HGF) was injected into the tumor every three days. After confirmed the growth tumor mass, 500 μL of GO-Y030 diluted with PBS were administrated intraperitoneally daily at doses of 1 mg/kg and 2 mg/kg, respectively.

RESULTS

GO-Y030 exhibits a growth inhibitory effect on malignant meningioma cell lines, IOMM-Lee and HKBMM ranging from 0.8-2.0 μM in vitro. Notably, GO-Y030’s inhibitory effect is about 10 to 16^th times more potent than that of curcumin, which has previously demonstrated potential in combating malignant meningioma. In mouse models, the intraperitoneal administration of GO-Y030 effectively suppresses the growth of malignant meningioma tumors that have been inoculated in the back (P = 0.002). High-performance liquid chromatography analysis has confirmed the distribution of GO-Y030 in the bloodstream and brain tissue. Moreover, GO-Y030 demonstrates the ability to significantly suppress HGF (P < 0.01), nuclear factor kappa B (P < 0.001), and N-cadherin (P < 0.001), all of which contribute to the epithelial-mesenchymal transition.

CONCLUSION

GO-Y030 holds promise as a potent compound for the systemic inhibition of malignant meningioma. GO-Y030 has higher tumor growth inhibitory effect against meningiomas than curcumin, which is known to have antitumor activity through multi-molecular target control resulting in apoptosis induction. GO-Y030 controls at least three molecules of HGF, nuclear factor kappa B, and N-cadherin.

Impact on natural history of atypical meningioma after changes in 2016 edition of the world health organization (WHO) classification of central nervous system tumors: a literature review

Meningiomas and their WHO histological diagnostic criteria is complex, especially for grade 2 tumors presenting a interobserver discordance as high as 12.2%. The 2016 edition of the WHO Classification of CNS tumors recommended brain invasion as a stand-alone grading criterion for diagnosing an atypical grade 2 meningioma (AM). To provide an overview of the classification of 2016 WHO impact on the natural history of atypical meningioma (AM) relative to previous classification. To achieve this goal, we selected articles from the period 2017-2024 in Medline search on atypical meningiomas and analyzed them after following the following criteria: 1) reports with confirmed histopathological diagnosis according to WHO 2016 and or 2021 criteria; 2) series and case reports; 3) detailed and individualized clinical outcomes for AM; and 4) papers written in English; after that a total of 3445 patients reported in 67 manuscripts from worldwide centers from 2017 to March 2024 were analyzed. The patient's age at the time of surgery ranged from 1 month to 97 years (mean 52.28 ± 18.7 years). The most common tumor site was the convexity, accounting for 67.8%, followed by the skull base in 30.6%, ventricle in 1%, and spine in 0.6%; Gross total resection (GTR) was performed in 71.25% and subtotal resection (STR) in 28.75%; 1021 patients (29.63%) underwent adjuvant radiotherapy, and 22 patients (0.6%) were treated with adjuvant chemotherapy; tumor recurrence was reported in 1221 patients (35.44%) and 859 deaths (24.93%). 1) AM prevalence in females; 2) AM age distribution similar to the distribution of meningiomas in general; 3) AM recurrence rate of 35.44%, despite the high rate of GTR, which was higher than previously reported; 4) deepening knowledge in molecular mechanism of tumor progression will provide alternative therapeutic approaches for AM.

RACK1 Promotes Meningioma Progression by Activation of NF-κB Pathway via Preventing CSNK2B from Ubiquitination Degradation

Higher-grade meningiomas (WHO grade II and III) are characterized by aggressive invasiveness and high postoperative recurrence rates. The prognosis remains inadequate even with adjuvant radiotherapy and currently there is no definitive pharmacological treatment strategy and target for malignant meningiomas. This study aims to unveil the mechanisms driving the malignant progression of meningiomas and to identify potential inhibitory targets, with significant clinical implications. Implementing techniques such as protein immunoprecipitation, mass spectrometry, RNA interference, and transcriptome sequencing, we investigated the malignancy mechanisms in meningioma cell lines IOMM-LEE and CH157-MN. Additionally, in vivo experiments were carried out on nude mice. We discovered a positive correlation between meningioma malignancy and the levels of the receptor for activated C kinase 1 (RACK1), which interacts with CSNK2B, the β subunit of casein kinase 2 (CK2), inhibiting its ubiquitination and subsequent degradation. This inhibition allows CK2 to activate the NF-κb pathway, which increases the transcription of CDK4 and cyclin D3, resulting in the transition of the cell cycle into the G2/M phase. The RACK1 inhibitor, harringtonolide (HA), significantly suppressed the malignant tendencies of meningioma cells. Our study suggests that RACK1 may play a role in the malignant progression of meningiomas, and therefore, targeting RACK1 could emerge as an effective strategy for reducing the malignancy of these tumors.

The role of radiation therapy and systemic treatments in meningioma: The present and the future

Meningiomas are the most prevalent tumors of the central nervous system. Their standard treatment is surgery, which can be curative. Adjuvant radiotherapy treatment is reserved for newly diagnosed cases of grade II and grade III meningiomas in cases of recurrent disease or when surgery is not radical or feasible. However, around 20% of these patients cannot undergo further surgical and/or radiotherapy treatment. Systemic oncological therapy can find its place in this setting. Several tyrosine kinase inhibitors have been tested (gefitinib, erlotinib, sunitinib) with unsatisfactory or negative results. Bevacizumab has shown encouraging results in these settings of patients. Immunotherapy with immune checkpoint inhibitors has reported interesting results with modest objective response rates. Several ongoing studies are assessing different target therapies and multimodal therapies; the results are to be disclosed. Not only a better understanding of the molecular characteristics in meningiomas has allowed the gathering of more information regarding pathogenesis and prognosis, but in addition, the availability of new target therapy, immunotherapy, and biological drugs has widened the scope of potentially effective treatments in this patient population. The aim of this review was to explore the radiotherapy and systemic treatments of meningioma with an analysis of ongoing trials and future therapeutic perspectives.

Advances in Molecular Biological and Translational Studies in World Health Organization Grades 2 and 3 Meningiomas: A Literature Review

The treatment of World Health Organization (WHO) grades 2 and 3 meningiomas remains difficult and controversial. The pathogenesis of high-grade meningiomas was expected to be elucidated to improve treatment strategies. The molecular biology of meningiomas has been clarified in recent years. High-grade meningiomas have been linked to NF2 mutations and 22q deletion. CDKN2A/B homozygous deletion and TERT promoter mutations are independent prognostic factors for WHO grade 3 meningiomas. In addition to 22q loss, 1p, 14p, and 9q loss have been linked to high-grade meningiomas. Meningiomas enriched in copy number alterations may be biologically invasive. Furthermore, several new comprehensive classifications of meningiomas have been proposed based on these molecular biological features, including DNA methylation status. The new classifications may have implications for treatment strategies for refractory aggressive meningiomas because they provide a more accurate prognosis compared to the conventional WHO classification. Although several systemic therapies, including molecular targeted therapies, may be effective in treating refractory aggressive meningiomas, these drugs are being tested. Systemic drug therapy for meningioma is expected to be developed in the future. Thus, this review aims to discuss the distinct genomic alterations observed in WHO grade 2 and 3 meningiomas, as well as their diagnostic and therapeutic implications and systemic drug therapies for high-grade meningiomas.

Bone Invasive Meningioma: Recent Advances and Therapeutic Perspectives

Meningioma is the most common primary neoplasm of the central nervous system (CNS). Generally, these tumors are benign and have a good prognosis. However, treatment can be challenging in cases with aggressive variants and poor prognoses. Among various prognostic factors that have been clinically investigated, bone invasion remains controversial owing to a limited number of assessments. Recent study reported that bone invasion was not associated with WHO grades, progression, or recurrence. Whereas, patients with longer-recurrence tended to have a higher incidence of bone invasion. Furthermore, bone invasion may be a primary preoperative predictor of the extent of surgical resection. Increasing such evidence highlights the potential of translational studies to understand bone invasion as a prognostic factor of meningiomas. Therefore, this mini-review summarizes recent advances in pathophysiology and diagnostic modalities and discusses future research directions and therapeutic strategies for meningiomas with bone invasion.

Consensus core clinical data elements for meningiomas

BACKGROUND

With increasing molecular analyses of meningiomas, there is a need to harmonize language used to capture clinical data across centers to ensure that molecular alterations are appropriately linked to clinical variables of interest. Here the International Consortium on Meningiomas presents a set of core and supplemental meningioma-specific Common Data Elements (CDEs) to facilitate comparative and pooled analyses.

METHODS

The generation of CDEs followed the four-phase process similar to other National Institute of Neurological Disorders and Stroke (NINDS) CDE projects: discovery, internal validation, external validation, and distribution.

RESULTS

The CDEs were organized into patient- and tumor-level modules. In total, 17 core CDEs (10 patient-level and 7-tumour-level) as well as 14 supplemental CDEs (7 patient-level and 7 tumour-level) were defined and described. These CDEs are now made publicly available for dissemination and adoption.

CONCLUSIONS

CDEs provide a framework for discussion in the neuro-oncology community that will facilitate data sharing for collaborative research projects and aid in developing a common language for comparative and pooled analyses. The meningioma-specific CDEs presented here are intended to be dynamic parameters that evolve with time and The Consortium welcomes international feedback for further refinement and implementation of these CDEs.

DMD genomic deletions characterize a subset of progressive/higher-grade meningiomas with poor outcome

Progressive meningiomas that have failed surgery and radiation have a poor prognosis and no standard therapy. While meningiomas are more common in females overall, progressive meningiomas are enriched in males. We performed a comprehensive molecular characterization of 169 meningiomas from 53 patients with progressive/high-grade tumors, including matched primary and recurrent samples. Exome sequencing in an initial cohort (n = 24) detected frequent alterations in genes residing on the X chromosome, with somatic intragenic deletions of the dystrophin-encoding and muscular dystrophy-associated DMD gene as the most common alteration (n = 5, 20.8%), along with alterations of other known X-linked cancer-related genes KDM6A (n =2, 8.3%), DDX3X, RBM10 and STAG2 (n = 1, 4.1% each). DMD inactivation (by genomic deletion or loss of protein expression) was ultimately detected in 17/53 progressive meningioma patients (32%). Importantly, patients with tumors harboring DMD inactivation had a shorter overall survival (OS) than their wild-type counterparts [5.1 years (95% CI 1.3-9.0) vs. median not reached (95% CI 2.9-not reached, p = 0.006)]. Given the known poor prognostic association of TERT alterations in these tumors, we also assessed for these events, and found seven patients with TERT promoter mutations and three with TERT rearrangements in this cohort (n = 10, 18.8%), including a recurrent novel RETREG1-TERT rearrangement that was present in two patients. In a multivariate model, DMD inactivation (p = 0.033, HR = 2.6, 95% CI 1.0-6.6) and TERT alterations (p = 0.005, HR = 3.8, 95% CI 1.5-9.9) were mutually independent in predicting unfavorable outcomes. Thus, DMD alterations identify a subset of progressive/high-grade meningiomas with worse outcomes.

Octreotide therapy in meningiomas: in vitro study, clinical correlation, and literature review

OBJECTIVE Meningiomas express somatostatin receptor subtype 2 (SST2), which is targeted by the somatostatin analog octreotide. However, to date, using somatostatin analog therapy for the treatment of these tumors in clinical practice has been debated. This study aims to clarify the in vitro effects of octreotide on meningiomas for precise clinical applications. METHODS The effects of octreotide were analyzed in a large series of 80 meningiomas, including 31 World Health Organization (WHO) Grade II and 4 WHO Grade III tumors, using fresh primary cell cultures to study the impact on cell viability, apoptosis, and signal transduction pathways. RESULTS SST2 mRNA was detected in 100% of the tested meningiomas at levels similar to those observed in other SST2-expressing tumors, neuroendocrine tumors, or pituitary adenomas. Octreotide significantly decreased cell proliferation in 88% of meningiomas but did not induce cell death. On average, cell proliferation was more inhibited in the meningioma group expressing a high level of SST2 than in the low-SST2 group. Moreover, octreotide response was positively correlated to the level of merlin protein and inversely correlated to the level of phosphorylated p70-S6 kinase, a downstream effector of the PI3K/Akt/mammalian target of rapamycin (mTOR) pathway. Octreotide inhibited Akt phosphorylation and activated tyrosine phosphatase without impacting the extracellular regulated kinase (ERK) pathway. CONCLUSIONS Octreotide acts exclusively as an antiproliferative agent and does not promote apoptosis in meningioma in vitro. Therefore, in vivo, octreotide is likely to limit tumor growth rather than induce tumor shrinkage. A meta-analysis of the literature reveals an interest in octreotide for the treatment of WHO Grade I tumors, particularly those in the skull base for which the 6-month progression-free survival level reached 92%. Moreover, somatostatin analogs, which are well-tolerated drugs, could be of interest for use as co-targeting therapies for aggressive meningiomas.

Boron Neutron Capture Therapy for Malignant Brain Tumors

Boron neutron capture therapy (BNCT) is a biochemically targeted radiotherapy based on the nuclear capture and fission reactions that occur when non-radioactive boron-10, which is a constituent of natural elemental boron, is irradiated with low energy thermal neutrons to yield high linear energy transfer alpha particles and recoiling lithium-7 nuclei. Therefore, BNCT enables the application of a high dose of particle radiation selectively to tumor cells in which boron-10 compound has been accumulated. We applied BNCT using nuclear reactors for 167 cases of malignant brain tumors, including recurrent malignant gliomas, newly diagnosed malignant gliomas, and recurrent high-grade meningiomas from January 2002 to May 2014. Here, we review the principle and history of BNCT. In addition, we introduce fluoride-18-labeled boronophenylalanine positron emission tomography and the clinical results of BNCT for the above-mentioned malignant brain tumors. Finally, we discuss the recent development of accelerators producing epithermal neutron beams. This development could provide an alternative to the current use of specially modified nuclear reactors as a neutron source, and could allow BNCT to be performed in a hospital setting.

Systemic therapy for recurrent meningioma

INTRODUCTION

Meningioma comprise 20-30% of all primary brain tumors. Notwithstanding surgery and radiotherapy, a subset of patients will manifest recurrent meningioma. Systemic therapy is recommended only when further surgery and radiotherapy are not possible. No prospective study with a high level of evidence is available to inform as to recommendations regarding systemic therapy.

AREAS COVERED

We aim to summarize systemic therapies for recurrent meningioma. Expert commentary: Hydroxurea, temozolomide, irinotecan, the combination of cyclophosphamide/adriamycine/vincristine, interferon-alpha, somatostatin analogs, mifepristone, megestrol acetate, imatinib, erlotinib and gefitinib are considered as having limited efficacy. Potential activity of VEGF (vascular endothelial growth factor) inhibitors such as sunitinib, valatinib, and bevacizumab is suggested in small non-controlled studies and requires validation in randomized trials. The identification of new prognostic markers such as TERT promoter mutations and potential new therapeutic targets, such as KLF4, AKT1, TRAF7, and SMO mutations hopefully facilitate this endeavor.

p38MAPK activation and DUSP10 expression in meningiomas

The mitogen activated protein kinase (MAPK) p38MAPK has been implicated in regulation of cell proliferation and apoptosis. However, expression, activation and regulation has not been studied in meningiomas, to our knowledge. p38MAPK is regulated, in part, by dual specificity phosphatases (DUSP) that inactivate signaling by dephosphorylation. DUSP10 is also a likely participant in regulating meningioma proliferation. Five fetal and an adult human leptomeninges and 37 meningioma cultures (MC) were evaluated for DUSP10 as well as phosphorylation of its substrates p38MAPK and p44/42MAPK by western blot and DUSP10 expression by polymerase chain reaction. Platelet derived growth factor-BB (PDGF-BB), transforming growth factor B1 (TGFB1) and cerebrospinal fluid effects on DUSP10 and signaling were also studied in vitro. DUSP10 and phospho-p38MAPK and phospho-p44/42MAPK were detected in all six leptomeninges. DUSP10 was detected in 13 of 17 World Health Organization grade I, 11 of 14 grade II and four of six grade III meningiomas. Phospho-p38MAPK was detected in nine of 17 grade I, two of six grade II, and four of six grade III meningiomas. In the majority of meningiomas DUSP10 expression correlated inversely with phosphorylation of p38MAPK. PDGF-BB increased DUSP10 in MC2 and MC4 and weakly in MC3. TGFB1 increased phosphorylation of p38MAPK and caspase 3 activation. Thus p38MAPK and DUSP10 likely participate in the pathogenesis of meningiomas.

A five year-old child with clear cell petro-clival meningioma: case report with clinical and histopathological long-term follow-up

BACKGROUND

Only a few cases have been previously published about clear cell meningiomas in children, the majority of them in the location of the spine. We describe an unusual case of clear cell meningioma occurring at the petro-clival region in a 5-year-old child. We further seek to determine the impact of several growth factors as well as the AKT1 mutation on the tumor growth pattern.

CASE PRESENTATION

A five-year-old girl was presented with a one-week history of cephalgia, ataxia, and left sided torticollis. Magnetic resonance imaging (MRI) revealed a dumbbell-shaped homogeneously petro-clival gadolinium-enhancing mass. A staged operative approach was chosen, and a complete removal of the tumor was achieved. Due to recurrent tumor progression, the child underwent several tumor surgeries and two cranial radiations. None of the treatments were able to stop tumor progression. Consequently, the child died at the age of 14 after further extensive intracranial and extracranial tumor progression. The initial histological examination revealed a clear cell meningioma WHO grade II with an MIB-1 labeling index of <1%, which gradually increased with every recurrence up to 10% by the last progression at the age of 13 years. Analogically, an increasing overexpression of epidermal growth factor receptor (EGFR), the platelet-derived growth factor receptor (PDGFR), and the vascular endothelial growth factor receptor (VEGFR) was observed with each recurrence. The AKT1 (E17K) mutation in the tumor was not detectable in all investigated specimens.

CONCLUSION

Pediatric clear cell meningiomas WHO grade II are very rare. Our data demonstrate the progressive overexpression of EGF-, PDGF-, and VEGF-receptors in each recurrence, providing one of these receptors as targeted therapy in such cases. Further evaluation of these growth factors in clear cell meningioma is required to establish the optimal treatment of these aggressive tumors.

Malignant progression to anaplastic meningioma: Neuropathology, molecular pathology, and experimental models

Meningioma is a common adult intracranial tumor, and while several cases are considered benign, a subset is malignant with biologically aggressive behavior and is refractory to current treatment strategies of combined surgery and radiotherapy. Anaplastic meningiomas are quite aggressive and correspond to a World Health Organization (WHO) Grade III tumor. This highly aggressive phenotype mandates the need for more efficacious therapies. Designing rational therapies for treatment will have its foundation in the biologic understanding of involved genes and molecular pathways in these types of tumors. Anaplastic meningiomas (WHO Grade III) can arise from malignant transformation of lower grade (WHO Grade I/II) tumors, however there is an incomplete understanding of specific genetic drivers of malignant transformation in these tumors. Here, the current understanding of anaplastic meningiomas is reviewed in the context of human neuropathologic specimens and small animal models.

The importance of microsurgery in childhood meningioma: a case report

INTRODUCTION

Although meningiomas are frequently diagnosed in adults, it is a rare (intracranial) tumor in the pediatric population, with an incidence of 0.06/100,000. The pathology and treatment of meningiomas in adulthood has been a topic of increasing investigation. So far, the treatment of pediatric meningiomas has been extrapolated from these results. The question remains, however, whether translation of adult meningioma data into the childhood population is legitimate.

METHODS

We present the case of a 3-year-old girl diagnosed with an intraventricular malignant meningioma and type 2 neurofibromatosis. She was operated on multiple times to achieve complete resection and received adjuvant chemotherapy. Since, she has been stable with no neurological sequelae and/or recurrence of the meningioma.

CONCLUSION

Pediatric meningiomas are rare tumors and differ from their adult counterparts in various aspects. We believe that gross total resection of meningioma in the pediatric population, when possible, is the treatment of choice. In the event of a subtotal resection, repeat resection is recommended. Any adjuvant treatment with chemotherapy or radiation therapy should be carefully considered during multidisciplinary meetings.

A case of recurrent anaplastic meningioma of the skull base with radiologic response to hydroxyurea

Anaplastic meningiomas are rare and aggressive tumors with a high propensity for local recurrence. Surgical resection and postoperative radiotherapy are the standard of care for primary disease and local recurrences. Refractory disease is managed with chemotherapy with limited success. A highly efficacious, well-tolerated chemotherapeutic agent has yet to be found for this disease entity. Hydroxyurea is currently receiving renewed attention because of its efficacy in inducing apoptosis of meningioma cells in vitro and its favorable side-effect profile. Thus far, in humans, this agent has only induced stable disease.

We describe the first patient showing a near complete/partial clinical and radiological regression after 5 months of 25 mg/kg of hydroxyurea once daily, given within 1 month after stereotactic fractionated reirradiation of a previously irradiated and operated anaplastic meningioma of the skull base. Magnetic resonance imaging showed a significant and sustained response with tumor shrinkage and cavitation.

Recurrent high-grade meningioma: a phase II trial with somatostatin analogue therapy

PURPOSE

A prospective, two-stage phase II trial with octreotide in patients with recurrent high-grade meningioma was conducted. The radiographic partial response (RPR) was set as the primary study endpoint, whereas progression-free survival at 6 months (PFS6) was defined as the secondary endpoint.

METHODS

Nine patients (eight men; median age 65) with histological high-grade meningioma (five with grade II and four with grade III) and progression after prior surgery and radiotherapy were included. All had positive brain octreotide SPECT scanning. Octreotide was administered intramuscularly once every 28 days at a dose of 30 mg for the first two cycles and 40 mg for subsequent cycles until progression. Magnetic resonance imaging was performed every 3 months. Progression and RPR were defined as an increase of ≥25 % and as a decrease of ≥50 % in two-dimensional maximum diameters, respectively.

RESULTS

Patients received a median of three octreotide cycles (range 1-8) without grade ≥2 toxicities. No RPRs were observed. Stable disease was the best response in 33.3 % (n = 3). All patients had progressive disease at 10 months of follow-up. Median time to progression was 4.23 months (range 1-9.4), and the PFS6 was 44.4 % (n = 4).

CONCLUSION

Our study failed to provide evidence to support the use of monthly long-acting somatostatin analogue schedule in recurrent high-grade meningiomas, as none of our patients demonstrated RPR. The modest median PFS of 4-5 months along with the unknown natural history of recurrent meningiomas render the use of this therapy against these aggressive brain tumors uncertain.

Role of external beam radiotherapy in the treatment of relapsing meningioma

The role of radiotherapy in the treatment of relapsing meningiomas is not well established. Data of patients treated with radiotherapy for a relapsing meningioma were retrospectively analyzed. Overall survival (OS) was the primary endpoint of the analysis. Local control and acute and late toxicity rates have been also reported. From April 1986 to February 2011, 37 patients with a diagnosis of recurrent meningioma were treated. Median age was 64 years (range 36-79). A total of 18, 10, 5 and 4 patients were affected by relapsing benign, atypical, malignant meningiomas and meningiosarcomas, respectively (WHO classification). Median dose was 60 Gy (range 46-66 Gy). The median follow-up was 42 months (range 3-300 months). OS at 1, 3, 5 and 8 years was 81, 55.6, 43.9 and 25.8%, respectively (median OS 45 months). A strong statistical trend was observed toward better OS rates in patients treated with radiotherapy at first recurrence compared to those treated at the second (or more) recurrence (OS 50.5 vs. 30.8%, p=0.055). A statistical impact of the histology (WHO I vs. II, III and IV) on 5-year OS was also observed (OS 60 vs. 30%, 0 and 0%, p=0.010). Radiotherapy has been well tolerated, with no G2-4 neurological toxicity (RTOG toxicity score). Conventional radiation therapy has an important role in multidisciplinary approach in the treatment of recurrence of meningiomas. The histological type and the timing of the radiotherapy are prognostic factors in terms of survival.

Current standing and frontiers of gene therapy for meningiomas

Meningiomas are among the most common intracranial tumors. The treatment of choice for these lesions is complete resection, but in 50% of cases it is not achieved due to tumor location and/or surgical morbidities. Moreover, benign meningiomas have high recurrence rates of up to 32% in long-term follow-up. Molecular analyses have begun to uncover the genetics behind meningiomas, giving rise to potential genetics-based treatments, including gene therapy. The authors performed a literature review on the most relevant genes associated with meningiomas and both current and potential gene therapy strategies to treat these tumors. Wild-type NF2 gene insertion, oncolytic viruses, and transfer of silencing RNA have all shown promising results both in vitro and in mice. These strategies have decreased meningioma cell growth, proliferation, and angiogenesis. However, no clinical trial has been done to date. Future research and trials in gene insertion, selective inhibition of oncogenes, and the use of oncolytic viruses, among other potential treatment approaches, may shape the future of meningioma management.

Boron neutron capture therapy for recurrent high-grade meningiomas

OBJECT

Similar to glioblastomas, high-grade meningiomas are difficult pathologies to control. In this study, the authors used boron neutron capture therapy (BNCT), a tumor-selective intensive particle radiation modality, to treat high-grade meningioma.

METHODS

From June 2005 to September 2011, BNCT was applied 28 times in 20 cases of recurrent high-grade meningioma. All patients had previously undergone intensive treatments such as repetitive surgeries and multiple sessions of radiation therapy. Fluorine-18-labeled boronophenylalanine ((18)F-BPA) PET was performed before BNCT in 19 of the 20 cases; BPA is itself a therapeutic compound. Compound uptake, tumor shrinkage, long-term control rate including survival time, and failure pattern of the treated patients were all evaluated.

RESULTS

Eighteen of 19 cases studied using (18)F-BPA PET showed good BPA uptake, with ratios of tumor to normal brain greater than 2.7. These ratios indicated the likely effects of BNCT prior to neutron irradiation. The original tumor sizes were between 4.3 cm(3) and 109 cm(3). A mean tumor volume reduction of 64.5% was obtained after BNCT within just 2 months. The median follow-up duration was 13 months. Six patients are still alive; at present, the median survival times after BNCT and diagnosis are 14.1 months (95% CI 8.6-40.4 months) and 45.7 months (95% CI 32.4-70.7 months), respectively. Clinical symptoms before BNCT, such as hemiparesis and facial pain, were improved after BNCT in symptomatic cases. Systemic metastasis, intracranial distant recurrence outside the radiation field, CSF dissemination, and local tumor progression were observed in 6, 7, 3, and 3 cases, respectively, during the clinical course. Apparent pseudoprogression was observed in at least 3 cases. Symptomatic radiation injuries occurred in 6 cases, and were controllable in all but 1 case.

CONCLUSIONS

Boron neutron capture therapy may be especially effective in cases of high-grade meningioma.

Peptide receptor targeting in cancer: the somatostatin paradigm

Peptide receptors involved in pathophysiological processes represent promising therapeutic targets. Neuropeptide somatostatin (SST) is produced by specialized cells in a large number of human organs and tissues. SST primarily acts as inhibitor of endocrine and exocrine secretion via the activation of five G-protein-coupled receptors, named sst1–5, while in central nervous system, SST acts as a neurotransmitter/neuromodulator, regulating locomotory and cognitive functions. Critical points of SST/SST receptor biology, such as signaling pathways of individual receptor subtypes, homo- and heterodimerization, trafficking, and cross-talk with growth factor receptors, have been extensively studied, although functions associated with several pathological conditions, including cancer, are still not completely unraveled. Importantly, SST exerts antiproliferative and antiangiogenic effects on cancer cells in vitro, and on experimental tumors in vivo. Moreover, SST agonists are clinically effective as antitumor agents for pituitary adenomas and gastro-pancreatic neuroendocrine tumors. However, SST receptors being expressed by tumor cells of various tumor histotypes, their pharmacological use is potentially extendible to other cancer types, although to date no significant results have been obtained. In this paper the most recent findings on the expression and functional roles of SST and SST receptors in tumor cells are discussed.