Simultaneous inhibition of PI3K and PAK in preclinical models of neurofibromatosis type 2-related schwannomatosis

Neurofibromatosis Type 2 (NF2)-related schwannomatosis is a genetic disorder that causes development of multiple types of nervous system tumors. The primary and diagnostic tumor type is bilateral vestibular schwannoma. There is no cure or drug therapy for NF2. Recommended treatments include surgical resection and radiation, both of which can leave patients with severe neurological deficits or increase the risk of future malignant tumors. Results of our previous pilot high-throughput drug screen identified phosphoinositide 3-kinase (PI3K) inhibitors as strong candidates based on loss of viability of mouse merlin-deficient Schwann cells (MD-SCs). Here we used novel human schwannoma model cells to conduct combination drug screens. We identified a class I PI3K inhibitor, pictilisib and p21 activated kinase (PAK) inhibitor, PF-3758309 as the top combination due to high synergy in cell viability assays. Both single and combination therapies significantly reduced growth of mouse MD-SCs in an orthotopic allograft mouse model. The inhibitor combination promoted cell cycle arrest and apoptosis in mouse merlin-deficient Schwann (MD-SCs) cells and cell cycle arrest in human MD-SCs. This study identifies the PI3K and PAK pathways as potential targets for combination drug treatment of NF2-related schwannomatosis.

Cotargeting Phosphoinositide 3-Kinase and Focal Adhesion Kinase Pathways Inhibits Proliferation of NF2 Schwannoma Cells

Neurofibromatosis Type 2 (NF2) is a tumor predisposition syndrome caused by germline inactivating mutations in the NF2 gene encoding the merlin tumor suppressor. Patients develop multiple benign tumor types in the nervous system including bilateral vestibular schwannomas (VS). Standard treatments include surgery and radiation therapy, which may lead to loss of hearing, impaired facial nerve function, and other complications. Kinase inhibitor monotherapies have been evaluated clinically for NF2 patients with limited success, and more effective nonsurgical therapies are urgently needed. Schwannoma model cells treated with PI3K inhibitors upregulate activity of the focal adhesion kinase (FAK) family as a compensatory survival pathway. We screened combinations of 13 clinically relevant PI3K and FAK inhibitors using human isogenic normal and merlin-deficient Schwann cell lines. The most efficacious combination was PI3K/mTOR inhibitor omipalisib with SRC/FAK inhibitor dasatinib. Sub-GI50 doses of the single drugs blocked phosphorylation of their major target proteins. The combination was superior to either single agent in promoting a G1 cell-cycle arrest and produced a 44% decrease in tumor growth over a 2-week period in a pilot orthotopic allograft model. Evaluation of single and combination drugs in six human primary VS cell models revealed the combination was superior to the monotherapies in 3 of 6 VS samples, highlighting inter-tumor variability between patients consistent with observations from clinical trials with other molecular targeted agents. Dasatinib alone performed as well as the combination in the remaining three samples. Preclinically validated combination therapies hold promise for NF2 patients and warrants further study in clinical trials.

Metformin Reduces Tumor Growth in a Murine Flank Schwannoma Model

HYPOTHESIS

Metformin and aspirin reduce vestibular schwannoma (VS) growth.

BACKGROUND

There have been reported associations between patients with VS prescribed metformin and decreased tumor volumetric growth. Aspirin has also been associated with decreased VS growth in animal studies.

METHODS

Rat schwannoma cell lines were grown and implanted into 50 athymic nude mice. Tumors were grown to 5 mm, and then mice were injected with either low- or high-dose metformin, aspirin, or saline daily. Tumors were measured until 14 days elapsed or mice demonstrated symptoms such as ulceration, inability to walk, or passed away.

RESULTS

There were no significant differences in day 0 tumor sizes between the control and the treatment groups ( p = 0.73). In the low-dose, but not high-dose groups, day 7 volumes were significantly different for both metformin ( p = 0.04) and aspirin ( p = 0.02) compared with placebo. Mean tumor growth rates were 126.6 ± 65.6 mm 3 /day for saline compared with 73.7 ± 29.5 mm 3 /day for low-dose metformin ( p = 0.03) and 68.7 ± 34.8 mm 3 /day for low-dose aspirin ( p = 0.016). There were no significant differences in tumor sizes ( p = 0.59) or growth rates ( p = 0.75) between low-dose metformin and aspirin groups. Low-dose groups had treatment stopped at 14 days, with continued monitoring demonstrating significant increases in tumor growth off treatment for both aspirin ( p = 0.006) and metformin ( p = 0.048).

CONCLUSIONS

Metformin treatment significantly reduced VS growth to a similar level as aspirin. Furthermore, when removing both metformin and aspirin treatment, tumor growth significantly increased.

Proteasomal pathway inhibition as a potential therapy for NF2-associated meningioma and schwannoma

BACKGROUND

Neurofibromatosis 2 (NF2) is an inherited disorder caused by bi-allelic inactivation of the NF2 tumor suppressor gene. NF2-associated tumors, including schwannoma and meningioma, are resistant to chemotherapy, often recurring despite surgery and/or radiation, and have generally shown cytostatic response to signal transduction pathway inhibitors, highlighting the need for improved cytotoxic therapies.

METHODS

Leveraging data from our previous high-throughput drug screening in NF2 preclinical models, we identified a class of compounds targeting the ubiquitin-proteasome pathway (UPP), and undertook studies using candidate UPP inhibitors, ixazomib/MLN9708, pevonedistat/MLN4924, and TAK-243/MLN7243. Employing human primary and immortalized meningioma (MN) cell lines, CRISPR-modified Schwann cells (SCs), and mouse Nf2-/- SCs, we performed dose response testing, flow cytometry-based Annexin V and cell cycle analyses, and RNA-sequencing to identify potential underlying mechanisms of apoptosis. In vivo efficacy was also assessed in orthotopic NF2-deficient meningioma and schwannoma tumor models.

RESULTS

Testing of three UPP inhibitors demonstrated potent reduction in cell viability and induction of apoptosis for ixazomib or TAK-243, but not pevonedistat. In vitro analyses revealed that ixazomib or TAK-243 downregulates expression of c-KIT and PDGFRα, as well as the E3 ubiquitin ligase SKP2 while upregulating genes associated with endoplasmic reticulum stress-mediated activation of the unfolded protein response (UPR). In vivo treatment of mouse models revealed delayed tumor growth, suggesting a therapeutic potential.

CONCLUSIONS

This study demonstrates the efficacy of proteasomal pathway inhibitors in meningioma and schwannoma preclinical models and lays the groundwork for use of these drugs as a promising novel treatment strategy for NF2 patients.

Drug Repositioning for Refractory Benign Tumors of the Central Nervous System

Drug repositioning (DR) is the process of identifying novel therapeutic potentials for already-approved drugs and discovering new therapies for untreated diseases. DR can play an important role in optimizing the pre-clinical process of developing novel drugs by saving time and cost compared with the process of de novo drug discovery. Although the number of publications related to DR has rapidly increased, most therapeutic approaches were reported for malignant tumors. Surgical resection represents the definitive treatment for benign tumors of the central nervous system (BTCNS). However, treatment options remain limited for surgery-, chemotherapy- and radiation-refractory BTCNS, as well as malignant tumors. Meningioma, pituitary neuroendocrine tumor (PitNET), and schwannoma are the most common BTCNS. The treatment strategy using DR may be applied for refractory BTCNS, such as Grade 2 meningiomas, neurofibromatosis type 2-related schwannomatosis, and PitNETs with cavernous sinus invasion. In the setting of BTCNS, stable disease can provide significant benefit to the patient. DR may provide a longer duration of survival without disease progression for patients with refractory BTCNS. This article reviews the utility of DR for refractory BTCNS.

18F-FDG PET/CT imaging for aggressive melanotic schwannoma of the L3 spinal root: A case report

RATIONALE

Melanotic schwannoma (MS) is an unusual variant of a nerve sheath neoplasm that accounts for less than 1% of all primary peripheral nerve sheath tumors. Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has unique value in detecting malignant MS lesions. To date, only 4 cases of MS with hepatic metastasis have been reported. Herein, we report the fifth case, which is the first reported patient with MS of Asian ethnicity with hepatic metastasis.

PATIENT CONCERNS

A 29-year-old woman with a 1-day history of backache was admitted to our hospital. PET/CT showed a paravertebral heterogeneous soft tissue mass along the spinal nerve at the L2-L3 level with strong FDG uptake, and a nodule with increased FDG uptake in the lateral lobe of the left liver.

DIAGNOSIS

A puncture biopsy of the L3 bony destruction and surrounding soft tissue mass was performed. The final diagnosis was spinal MS with hepatic metastasis.

INTERVENTIONS

The patient underwent 6 courses of systemic chemotherapy.

OUTCOMES

The patient did not receive further treatment for half a year after the end of chemotherapy and recovered well.

LESSONS

Unlike conventional schwannomas, which are completely benign, MS has an unpredictable prognosis. It is thought to have low malignant potential, and the malignant type tends to metastasize. FDG PET/CT has a unique and important value in the differential diagnosis of benign and malignant lesions, in detecting occult metastases, monitoring the treatment response, and assessing the prognosis of MS.

Novel response to neoadjuvant anti-PD1 therapy for a patient with retrocaval melanotic schwannoma

Melanotic schwannoma is a rare nerve sheath tumor composed of melanin-producing Schwann cells with the potential for metastasis. These tumors can be associated with familial tumor syndromes and can cause significant symptoms related to nerve compression and mass effect. Due to the rarity of these lesions, they can be initially misidentified as melanocytomas, pigmented dermatofibrosarcoma protuberans, neurofibromas or malignant melanomas. Surgical excision is the mainstay of treatment with limited benefit from adjuvant systemic chemotherapy or radiation. Modern treatments with immune checkpoint blockade have demonstrated significant improvements in progression-free and overall survival for a variety of cancer histologies; however, anti-PD1 therapy has yet to be evaluated in patients with melanotic schwannoma. This report demonstrates a significant improvement in symptomatology and tumor stability with neoadjuvant anti-PD1 therapy for a retrocaval melanotic schwannoma initially masquerading as malignant melanoma. This report demonstrates the potential benefit of a novel therapeutic option for patients with melanotic schwannoma.

A proteasome-resistant fragment of NIK mediates oncogenic NF-κB signaling in schwannomas

Schwannomas are common, highly morbid and medically untreatable tumors that can arise in patients with germ line as well as somatic mutations in neurofibromatosis type 2 (NF2). These mutations most commonly result in the loss of function of the NF2-encoded protein, Merlin. Little is known about how Merlin functions endogenously as a tumor suppressor and how its loss leads to oncogenic transformation in Schwann cells (SCs). Here, we identify nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-inducing kinase (NIK) as a potential drug target driving NF-κB signaling and Merlin-deficient schwannoma genesis. Using a genomic approach to profile aberrant tumor signaling pathways, we describe multiple upregulated NF-κB signaling elements in human and murine schwannomas, leading us to identify a caspase-cleaved, proteasome-resistant NIK kinase domain fragment that amplifies pathogenic NF-κB signaling. Lentiviral-mediated transduction of this NIK fragment into normal SCs promotes proliferation, survival, and adhesion while inducing schwannoma formation in a novel in vivo orthotopic transplant model. Furthermore, we describe an NF-κB-potentiated hepatocyte growth factor (HGF) to MET proto-oncogene receptor tyrosine kinase (c-Met) autocrine feed-forward loop promoting SC proliferation. These innovative studies identify a novel signaling axis underlying schwannoma formation, revealing new and potentially druggable schwannoma vulnerabilities with future therapeutic potential.

False localizing sign caused by schwannoma in cervical spinal canal at C1-2 level: A case report

RATIONALE

False localizing sign means that the lesion, which is the cause of the symptom, is remote or distant from the anatomical site predicted by neurological examination. This concept contradicts the classical clinicoanatomical correlation paradigm underlying neurological examinations.

PATIENT CONCERNS

A 54-year-old man consulted for the right sciatica-like leg pain that had aggravated 1 year ago. Radiological examinations revealed degenerative spondylolisthesis with instability and right-sided recess stenosis at the L4-5 level. After initial improvement following 3 transforaminal epidural steroid injections with gabapentin and antidepressant medication, there was a recurrence of the symptoms a year later, along with wasting of the right leg for several months. Physical examination revealed difficulty in heel-walking and a weakness of extension of the right big toe; tendon reflexes were normal. Lumbar spine radiographs revealed no new findings. The initial course of treatment was repeated, but was ineffective.

DIAGNOSES

Further cervicothoracic spine evaluations revealed a right-sided intradural-extramedullary mass and myelopathy at the C1-2 level.

INTERVENTIONS

The cervical mass was surgically resected and identified histopathologically as a schwannoma.

OUTCOMES

Immediately after surgery, sciatica-like pain and weakness of right leg were completely resolved.

LESSONS

It is difficult to make an accurate diagnosis if there are symptoms caused by false localizing sign. Additionally, it is even more difficult to diagnose false localizing sign accurately when there is a co-existing lumbar lesion that can cause the similar symptoms.

Traditional and systems biology based drug discovery for the rare tumor syndrome neurofibromatosis type 2

Neurofibromatosis 2 (NF2) is a rare tumor suppressor syndrome that manifests with multiple schwannomas and meningiomas. There are no effective drug therapies for these benign tumors and conventional therapies have limited efficacy. Various model systems have been created and several drug targets have been implicated in NF2-driven tumorigenesis based on known effects of the absence of merlin, the product of the NF2 gene. We tested priority compounds based on known biology with traditional dose-concentration studies in meningioma and schwann cell systems. Concurrently, we studied functional kinome and gene expression in these cells pre- and post-treatment to determine merlin deficient molecular phenotypes. Cell viability results showed that three agents (GSK2126458, Panobinostat, CUDC-907) had the greatest activity across schwannoma and meningioma cell systems, but merlin status did not significantly influence response. In vivo, drug effect was tumor specific with meningioma, but not schwannoma, showing response to GSK2126458 and Panobinostat. In culture, changes in both the transcriptome and kinome in response to treatment clustered predominantly based on tumor type. However, there were differences in both gene expression and functional kinome at baseline between meningioma and schwannoma cell systems that may form the basis for future selective therapies. This work has created an openly accessible resource (www.synapse.org/SynodosNF2) of fully characterized isogenic schwannoma and meningioma cell systems as well as a rich data source of kinome and transcriptome data from these assay systems before and after treatment that enables single and combination drug discovery based on molecular phenotype.

Delivery of Therapeutic Proteins via Extracellular Vesicles: Review and Potential Treatments for Parkinson's Disease, Glioma, and Schwannoma

Extracellular vesicles present an attractive delivery vehicle for therapeutic proteins. They intrinsically contain many proteins which can provide information to other cells. Advantages include reduced immune reactivity, especially if derived from the same host, stability in biologic fluids, and ability to target uptake. Those from mesenchymal stem cells appear to be intrinsically therapeutic, while those from cancer cells promote tumor progression. Therapeutic proteins can be loaded into vesicles by overexpression in the donor cell, with oligomerization and membrane sequences increasing their loading. Examples of protein delivery for therapeutic benefit in pre-clinical models include delivery of: catalase for Parkinson's disease to reduce oxidative stress and thus help neurons to survive; prodrug activating enzymes which can convert a prodrug which crosses the blood-brain barrier into a toxic chemotherapeutic drug for schwannomas and gliomas; and the apoptosis-inducing enzyme, caspase-1 under a Schwann cell specific promoter for schwannoma. This therapeutic delivery strategy is novel and being explored for a number of diseases.

HDAC8, A Potential Therapeutic Target for the Treatment of Malignant Peripheral Nerve Sheath Tumors (MPNST)

Introduction

HDAC isoform-specific inhibitors may improve the therapeutic window while limiting toxicities. Developing inhibitors against class I isoforms poses difficulties as they share high homology among their catalytic sites; however, HDAC8 is structurally unique compared to other class I isoforms. HDAC8 inhibitors are novel compounds and have affinity for class I HDAC isoforms demonstrating anti-cancer effects; little is known about their activity in malignant peripheral nerve sheath tumors (MPNST). Recently, we demonstrated anti-MPNST efficacy of HDAC8i in human and murine-derived MPNST pre-clinical models; we now seek to consider the potential therapeutic inhibition of HDAC8 in MPNST.

Methods

Four Human MPNST cell lines, a murine-derived MPNST cell line, and two HDAC8 inhibitors (PCI-34051, PCI-48012; Pharmacyclics, Inc. Sunnyvale, CA) were studied. Proliferation was determined using MTS and clonogenic assays. Effects on cell cycle were determined via PI FACS analysis; effects on apoptosis were determined using Annexin V-PI FACS analysis and cleaved caspase 3 expression. In vivo growth effects of HDAC8i were evaluated using MPNST xenograft models. 2D gel electrophoresis and mass spectrometry were used to identify potential HDAC8 deacetylation substrates.

Results

HDAC8i induced cell growth inhibition and marked S-phase cell cycle arrest in human and murine-derived MPNST cells. Relative to control, HDAC8i induced apoptosis in both human and murine-derived MPNST cells. HDAC8i exhibited significant effects on MPNST xenograft growth (p=0.001) and tumor weight (p=0.02). Four potential HDAC8 substrate targets were identified using a proteomic approach: PARK7, HMGB1, PGAM1, PRDX6.

Conclusions

MPNST is an aggressive sarcoma that is notoriously therapy-resistant, hence the urgent need for improved anti-MPNST therapies. HDAC8 inhibition may be useful for MPNST by improving efficacy while limiting toxicities as compared to pan-HDACis.

Combinatorial therapy with tamoxifen and trifluoperazine effectively inhibits malignant peripheral nerve sheath tumor growth by targeting complementary signaling cascades

Chemotherapeutic agents effective against malignant peripheral nerve sheath tumors (MPNSTs) are urgently needed. We recently found that tamoxifen potently impedes xenograft growth. In vitro, tamoxifen inhibits MPNST proliferation and survival in an estrogen receptor-independent manner; these effects are phenocopied by the calmodulin inhibitor trifluoperazine. The present study was performed to establish the mechanism of action of tamoxifen in vivo and optimize its therapeutic effectiveness. To determine if tamoxifen has estrogen receptor-dependent effects in vivo, we grafted MPNST cells in castrated and ovariectomized mice; xenograft growth was unaffected by reductions in sex hormones. To establish whether tamoxifen and trifluoperazine additively or synergistically impede MPNST growth, mice xenografted with neurofibromatosis type 1-associated or sporadic MPNST cells were treated with tamoxifen, trifluoperazine, or both drugs for 30 days. Both monotherapies inhibited graft growth by 50%, whereas combinatorial treatment maximally reduced graft mass by 90% and enhanced decreases in proliferation and survival. Kinomic analyses showed that tamoxifen and trifluoperazine have both shared and distinct targets in MPNSTs. In addition, trifluoperazine prevented tamoxifen-induced increases in serum/glucocorticoid regulated kinase 1, a protein linked to tamoxifen resistance. These findings suggest that combinatorial therapy with tamoxifen and trifluoperazine is effective against MPNSTs because these agents target complementary pathways that are essential for MPNST pathogenesis.

BNIP3 regulates AT101 [(-)-gossypol] induced death in malignant peripheral nerve sheath tumor cells

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive Schwann cell-derived sarcomas and are the leading cause of mortality in patients with neurofibromatosis type 1 (NF1). Current treatment modalities have been largely ineffective, resulting in a high rate of MPNST recurrence and poor five-year patient survival. This necessitates the exploration of alternative chemotherapeutic options for MPNST patients. This study sought to assess the cytotoxic effect of the BH3-mimetic AT101 [(-)-gossypol] on MPNST cells in vitro and to identify key regulators of AT101-induced MPNST cell death. We found that AT101 caused caspase-independent, non-apoptotic MPNST cell death, which was accompanied by autophagy and was mediated through HIF-1α induced expression of the atypical BH3-only protein BNIP3. These effects were mediated by intracellular iron chelation, a previously unreported mechanism of AT101 cytotoxicity.

Preclinical evaluation of the combination of mTOR and proteasome inhibitors with radiotherapy in malignant peripheral nerve sheath tumors

About one half of malignant peripheral nerve sheath tumors (MPNST) have Neurofibromin 1 (NF1) mutations. NF1 is a tumor suppressor gene essential for negative regulation of RAS signaling. Survival for MPNST patients is poor and we sought to identify an effective combination therapy. Starting with the mTOR inhibitors rapamycin and everolimus, we screened for synergy in 542 FDA approved compounds using MPNST cells with a native NF1 loss in both alleles. We further analyzed the cell cycle and signal transduction. In vivo growth effects of the drug combination with local radiation therapy (RT) were assessed in MPNST xenografts. The synergistic combination of mTOR inhibitors with bortezomib yielded a reduction in MPNST cell proliferation. The combination of mTOR inhibitors and bortezomib also enhanced the anti-proliferative effect of radiation in vitro. In vivo, the combination of mTOR inhibitor (everolimus) and bortezomib with RT decreased tumor growth and proliferation, and augmented apoptosis. The combination of approved mTOR and proteasome inhibitors with radiation showed a significant reduction of tumor growth in an animal model and should be investigated and optimized further for MPNST therapy.

Chemotherapy in metastatic malignant triton tumor: report on two cases

Malignant triton tumor (MTT) is a rare, highly malignant nerve sheath tumor with rhabdomyoblastic differentiation. Initial debulking surgery followed by adjuvant therapy is the current treatment of choice, but has very limited efficacy when optimal cytoreduction is not achieved by surgical procedure. Neoadjuvant therapy for MTT, to potentially facilitate subsequent surgery, eradicate micrometastatic lesions and, therefore, improve the therapeutical outcome, has never before been presented in literature. Here, we report on the multimodal management of two cases of advanced and metastatic MTT. Treatment modalities involved neoadjuvant and adjuvant chemotherapy, surgical resection, and radiation. In both cases, integrated Positron Emission Tomography/Computed Tomography (PET/CT) emerged as an important diagnostic tool for the reliable assessment of MTT response and metabolic remission.

The Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase Kinase Inhibitor PD184352 (CI-1040) Selectively Induces Apoptosis in Malignant Schwannoma Cell Lines

Type 1 neurofibromatosis (NF1) is a common autosomal dominant disorder that results in neuroectodermal tumors. The NF1 tumor-suppressor gene encodes neurofibromin, which includes a GTPase-activating domain for Ras inactivation. Affinity purification showed N-Ras to be the predominant activated isoform of Ras in two independent neurofibrosarcoma cell lines from NF1 patients (lines ST88-14 and NF90-8). These NF1 cells also demonstrated increased constitutive activity of the extracellular signal-regulated kinases 1 and 2 (ERK1,2) mitogen-activated protein (MAP) kinases compared with a sporadic malignant schwannoma cell line that maintains neurofibromin expression (STS-26T). Thus, MAP kinase kinase (MEK) inhibitors may be a rational approach to NF1 therapy. The MEK inhibitors PD98059 [2'-amino-3'-methoxyflavone], PD184352 (also called CI-1040) [2-(2-chloro-4-iodo-phenylamino)-N-cyclopropylmethoxy-3,4-difluoro-benzamide], and U0126 [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene] all produced concentration-dependent suppression of the proliferation of the three cell lines. Individual MEK inhibitors had similar effects in all three cell lines. However, only the antiproliferative effects of PD184352 correlated closely with the elimination of ERK1,2 MAP kinase activities. PD98059 was primarily cytostatic, whereas U0126 and PD184352 were cytotoxic. Only PD184352 induced apoptosis in all three lines, as indicated by morphology, activation of DEVDase, procaspase-3 cleavage, and the appearance of populations having sub-G(0)/G(1) DNA contents. The differential effects of the MEK inhibitors on cell survival were not dependent on p53 status or effects on the ERK5 pathway. PD184352 was also proapoptotic to primary rat Schwann cells. Hence, although PD184352 effectively killed neurofibrosarcoma cells, its effects on normal Schwann cells may limit its usefulness in the clinic.

[Rare case of retroperitoneal malignant Schwannoma]

Malignant Schwannoma, recently renamed malignant peripheral nerve sheat tumor retroperitoneally localized, represents 0.01 of retroperitoneal tumours. A 41-year old woman, without pathological record--and without cutaneous neurofibromatosis--hospitalized for increased volume of the abdomen, without symptomatology, is diagnosed after the imaging and biological tests--without CT and RMN--with retroperitoneal tumour. The unusual size of tumour--6000 gr.--the macroscopic aspect suggesting malignancy (histopathologically and immunohistochemically confirmed), the relatively easy extirpation which, nevertheless, required caudal spleen- and pancreatectomy as well as transvers colectomy, the absence of proximity adenopathy and remote secondary determinations, the simple postoperative evolution represent overwhelming elements in this case. Two years after the operation, during which the patient was under chemotherapy, on a routine control we found a relapse at a distance from the initial tumour (primitive tumour ?), totally operable. For the time being, after almost five years from the first operation, there are no clinical, biological and imaging changes.

CONCLUSIONS

the retroperitoneal space is quite enough for the development of large tumour masses, without symptomatology. The present case combines most characteristics of retroperitoneal neoplasms: large or very large size, quasi-absent symptomatology, difficulty in preoperative diagnosis, surgical tactics and techniques--quite often, the total extirpation of tumour mass led to the sacrifice of other organs within the limits of a justified risk--and unforeseeable evolution with relapses having the same characteristics.

Overexpression of the NF2 gene inhibits schwannoma cell proliferation through promoting PDGFR degradation

The loss of NF2 gene function leads to vestibular nerve schwannoma formation in humans. The NF2 gene product, Merlin/Schwannomin, has recently been found to interact with the two PDZ domains containing protein EBP50/NHE-RF, which is itself known to interact with the PDGF receptor (PDGFR) in several cell types. In this study, an up-regulation of both PDGFR and EBP50/NHE-RF, and an interaction of both proteins were found in primary human schwannoma tissue. Furthermore, using an adenoviral vector mediated gene transfer technique, changes in the phenotypic characteristics after NF2 gene restoration in a newly established NF2 gene-mutated human schwannoma cell line (HEI 193) were investigated. The overexpression of Merlin/Schwannomin in HEI 193 led to an inhibition of cell proliferation under serum-free conditions. Upon PDGF stimulation in culture, Merlin/Schwannomin appeared to inhibit the activation of the MAPK and PI3K signaling pathways, impinging on the phosphorylation of Erk 1/2 and Akt, respectively. The data also show that PDGFR is more rapidly internalized by the schwannoma cells overexpressing NF2. Therefore, this process is suggested as a model for a mechanism of Merlin/Schwannomin tumor suppressor function, which intermediates acceleration of the cell surface growth factor degradation.

Recurrent malignant Triton tumour: first report on a long time survivor

Malignant Triton tumour represents an extremely rare mesenchymal malignancy exhibiting histopathologic patterns of peripheral nerve sheath tumours and rhabdomyoblastic components, the latter usually determining the mostly fatal outcome. We report on a 26-year old patient diagnosed with malignant Triton tumour who developed multiple recurrences despite repeated aggressive surgery, chemo- and radiotherapy during an 8-year period. After Northern blotting analysis of an excised in-transit metastasis had revealed expression of retinoic receptors alpha and gamma, the patient received experimental treatment with isotretinoin and interferon-alpha for one year and remains without any evidence of disease for more than three years. This is the first report on a long-term survivor of multiple recurrences of malignant Triton tumour.

Carboplatin/etoposide induces remission of metastasised malignant peripheral nerve tumours (malignant schwannoma) refractory to first-line therapy

Malignant peripheral nerve tumours (MPNT), e.g. malignant schwannoma, represent a relatively rare tumour entity which is usually regarded as a member of the group of soft-tissue sarcomas and treated accordingly. For chemotherapeutic approaches in metastasised disease, ifosfamide and doxorubicin have been identified as the most efficient agents, with overall response rates distinctly less than 50%. In case of non-response, recommendations for effective second-line regimens are lacking. We present the case histories of two patients with pulmonary metastasised MPNT that was primarily refractory to ifosfamide/doxorubicin. Both patients developed a partial remission with tumour reduction exceeding 50% after treatment with carboplatin in combination with etoposide (CE), 150 mg/m2 each, days 1-4 in 4-week intervals. Complete resectability of lung metastases could be achieved, with histologic evidence for advanced tumour regression at the time of resection. Patients remain in stable complete remission 20 and 28 months after surgery, respectively. Major CE-associated toxicity was cumulative myelosuppression, especially thrombocytopenia, reaching WHO grade 4. To our knowledge, this is the first report showing that CE is a possibly successful chemotherapeutic regimen in advanced MPNT, although further studies are necessary to evaluate its efficacy.

[Sarcomas of the vulva. Report of 2 cases]

We report two cases of vulvar sarcomas that are our Institutional experience in 29 years. The first case was a teenager of 14 years-old with a low grade leiomyosarcoma surgically treated. Along a 22 years follow-up the disease has had four local recurrences of more than 5 cm each one: two after surgery and two after surgery plus chemotherapy and surgery plus radiotherapy respectively. She is alive disease evidence after two years from the last combined treatment. The second one, was a 26 years-old patient with a malignant schwannoma of 12 cm in diameter treated with combined radical surgery, radiotherapy, and chemotherapy. She is alive and without disease evidence 52 months after surgery. We emphasized that these tumors are very rare and the fact that the first patient is the youngest and with more years of follow up according the bibliography consulted. Treatment of vulvar sarcomas is radical local excision followed mainly by radiotherapy with infiltrating margins. The value of postoperative adjuvant chemotherapy is uncertain. According to the natural history and behavior of vulvar sarcomas, we conclude that the elective treatment of these tumors should be carry out in institutions of high level.

Enhanced proliferation and potassium conductance of Schwann cells isolated from NF2 schwannomas can be reduced by quinidine

Neurofibromatosis type 2 (NF2) is an autosomal dominant disease that is characterized mainly by schwannomas, as well as menigiomas and gliomas. The NF2 gene product merlin/schwannomin acts as a tumor suppressor. Schwann cells derived from NF2 schwannomas showed an enhanced proliferation rate, and electrophysological studies revealed larger K(+) outward currents as compared with controls. Schwann cells isolated from schwannomas of NF2 patients or multiorgan donors were treated with different concentrations of the K(+) current blockers quinidine, tetraethylammonium chloride, and 4-aminopyridine and K(+) outward currents and proliferation rates of these cells were compared. K(+) outward currents of both cell types can be blocked by quinidine. Importantly, treatment with quinidine reduces proliferation of NF2 Schwann cells in a concentration dependent manner but did not reduce proliferation of normal Schwann cells. Therefore, the use of quinidine or quinidine-like components would possibly provide a novel adjuvant therapeutic option for NF2 patients to slow down or freeze growth of schwannomas.

A case of malignant schwannoma with overexpression of multidrug resistance gene (MDR1) after chemotherapy

A 19-year-old:female patient with malignant schwannoma in the right knee was treated by combination chemotherapy including lipophilic anticancer compounds (cyclophosphamide, doxorubicin, vincristine and dacarbazine). The tumor was radically removed after chemotherapy, but metastatic lesions were noted in the right inguinal nodes. The patient died due to the cachexic state six months after surgery. In human neoplasm, P-glycoprotein (P-Gp) encoded by human multidrug resistance gene MDR1 is known to be related with multidrug resistant phenotype. Northern blot analysis revealed apparent MDR1 expression in the metastatic lesion, while the primary lesion showed faint MDR1 expression detected by only reverse transcriptase-polymerase chain reaction. P-Gp positive tumor cells were immunohistochemically detected both in the metastatic lesion and the primary lesion. The P-Gp-positive tumor cells in the metastatic lesion showed anaplastic features with highly atypical nuclei. These results suggest that MDR1 overexpression is related to the multidrug resistance phenomenon in the malignant schwannoma with morphological differences.

[A case report of malignant schwannoma of the chest wall]

We described a very rare case of malignant schwannoma of the chest wall, which was surgically resected. The patient, a 40-year-old woman, came to our hospital because of an abnormal shadow in the right chest wall of an X-ray film without any symptoms. Computed tomography revealed a solid tumor attached to the posteroinferior aspect of the intrathoracic chest wall. The tumor was a 2.5 x 2.1 cm, mass originating from the seventh intercostal nerve without pulmonary adhesion, and the patient underwent en bloc resection of the tumor. The pathological diagnosis was malignant schwannoma. The postoperative course was uneventful, and the patient, eight years after the operation is now doing well without local recurrence or distant metastasis. We reviewed seven cases of this type of tumor reported in the Japanese literature.

Human brain tumor O(6)-methylguanine-DNA methyltransferase mRNA and its significance as an indicator of selective chloroethylnitrosourea chemotherapy

O(6)-methylguanine-DNA methyltransferase (MGMT) removes and repairs chloroethylnitrosourea (CENU)-induced O(6)-methylguanine-DNA by accepting the alkyl group at a cysteine moiety. MGMT activity is, therefore, predictive of resistance or sensitivity to CENU chemotherapy. We measured the levels of MGMT mRNA expression in human brain tumors using a reverse transcription-polymerase chain reaction (RT-PCR) method, and studied the significance of MGMT mRNA levels in CENU chemotherapy. The level of MGMT mRNA was represented as a percentage relative to the MGMT mRNA in U138MG brain tumor cells. Forty-three patients with brain tumors were entered into the study. High-grade gliomas had significantly lower levels of MGMT mRNA than did low-grade gliomas and non-glial tumors (p < 0.05 determined by analysis of covariance). Out of 14 high-grade gliomas, 4 had a level of MGMT mRNA below 10%, indicating chemosensitivity to CENU. Out of 11 patients who received CENU chemotherapy, 3 had a partial response. All 3 responders had a low level of MGMT mRNA. The time to tumor progression (TTP) for 6 patients with a level lower than the median was short, but significantly longer than the TTP for 5 patients with a higher level (p < 0.05 determined by Gehan's Wilcoxon test). These results indicate that a fraction of brain tumors have a low expression of MGMT mRNA, and that the level of MGMT mRNA is a useful indicator of effectiveness in selective CENU chemotherapy.

Primary spinal malignant schwannoma

Malignant schwannomas are uncommon primary tumours of nerve sheath origin. They are rarely found within the spine and spinal canal, and little is known about their management in this unusual location. We describe the presentation of three patients with primary spinal malignant schwannomas and discuss the surgical management.

Growth inhibition of synchronized trigeminal neurinoma cells by nerve growth factor

Nerve growth factor (NGF) reduces the development of trigeminal neurinomas in vivo. To characterize the action of NGF on these tumors, clonal cells (476-16) isolated from a rat trigeminal neurinoma cell line were synchronized at early S phase by aphidicolin, a reversible inhibitor of DNA polymerase alpha, and effects of NGF on DNA replication were examined in vitro. While NGF did not inhibit DNA replication in the ongoing S phase, it reduced the level of DNA synthesis in the succeeding S phase without altering its timing and duration. The inhibitory action was elicited by a brief exposure to NGF during progression through the preceding S to G1 phases with decreasing effectiveness in the later stage of G1.

[A case of giant dumbbell tumor treated by one-stage operation]

A 39-year-old woman who had been diagnosed as having von Recklinghausen's disease came to our hospital due to numbness of the right fingers. A chest roentgenogram indicated a mass in the right upper thoracic cavity and MRI showed this mass to be a dumbbell shaped tumor connected to the spinal canal. Because we could secured the extension and invasion of the tumor by MRI, we could remove the tumor by a one-stage operation.

Inhibition of angiogenesis and growth of human nerve-sheath tumors by AGM-1470

The effectiveness of AGM-1470, a potent, fungal-derived inhibitor of angiogenesis, in suppressing the neovascularization and growth of human Schwann cell tumors was tested in six schwannomas, seven neurofibromas, and one neurofibrosarcoma. Tumor fragments from surgical specimens were implanted into the subrenal capsule of 348 nude mice (nu/nu). Seven days after implantation, the tumors were measured and vascularity was graded. The animals were then randomly assigned to one of two groups, to receive either saline (control group) or systemic AGM-1470 treatment. After 2 to 6 weeks of treatment, tumor size and degree of vascularity were recorded. In the six different schwannomas implanted into 138 mice, the average vascular grade in the control group after 2 weeks of treatment increased from 2.2 to 3.2 (+1.0), while in the AGM-1470-treated group it decreased from 2.2 to 1.7 (-0.5) (p < 0.01). In the seven different neurofibromas implanted into 158 mice, the change in the average vascular grade in control and AGM-1470-treated animals was +0.5 and -1.0, respectively (p < 0.01). In the one neurofibrosarcoma implanted into 52 mice, the change in average vascular grade in each group during the 6-week treatment period was +1.9 and -1.0, respectively (p < 0.01). Neurofibrosarcoma growth after 6 weeks of AGM-1470 treatment was only 8.5% of the growth found in the control animals (p < 0.01). This study determined that AGM-1470 is effective in inhibiting angiogenesis and the growth of human nerve-sheath tumors.

Fanconi's syndrome due to ifosfamide

Although renal wasting of phosphate is relatively common, Fanconi's syndrome following ifosfamide chemotherapy is rare. This case illustrates the possibility of developing Fanconi's syndrome despite the apparent lack of toxicity during previous ifosfamide exposure. As the use of high-dose ifosfamide-containing regimens prior to BMT increases, the occurrence of this adverse effect may become more frequent. Morbidity due to Fanconi's syndrome can be decreased by close monitoring and aggressive management of fluid and electrolytes.

Acute respiratory distress due to malignant schwannoma. A case report

A 13-year-old boy with acute respiratory distress due to a malignant schwannoma located in the neck, is reported. This case suggested that malignant schwannoma in the neck can lead to airway obstruction.

[Obstruction of the upper urinary tract caused by a malignant retrovesicular schwannoma. Therapeutic strategy]

We present a case of malignant Schwannoma (MS) of uncommon, retroperitoneal and retrovesical localization in a 42-year-old male, which provoked bilateral ureteral obstruction as a urological manifestation. We show our therapeutic strategy by means of a schedule of systemic neoadjuvant chemotherapy with vincristine, adriamycin, cyclophosphamide, decarbacine combined with exeresis and urinary continuity reconstruction surgery. We point out that it is a low incidence but highly aggressive tumour and that treatment continues to be local radical excision, whilst chemotherapy probably continues to have little value.

Malignant schwannoma of the clitoris in a 1-year-old child

A 1-year-old infant with von Recklinghausen's neurofibromatosis was seen because of increasing clitoral enlargement over a 7-month period. The mother, who also had neurofibromatosis, was treated 2 years beforehand for an acoustic neuroma. The child was treated by radical clitorectomy. Pathologic examination revealed malignant schwannoma, a tumor not previously described in this site. Vincristine, dactinomycin, and cyclophosphamide chemotherapy was given for 2 years to prevent local recurrence and metastatic spread. The child remains tumor free 2.5 years after diagnosis.

[Angiotensin II-induced hypertension chemotherapy of bone and soft-tissue sarcomas]

We treated 14 patients with high grade sarcomas by angiotensin II-induced hypertension chemotherapy. The chemotherapy protocol described by Rosen was selected according to histological classification of sarcomas (small cell sarcoma, spindle cell sarcoma, pleomorphic sarcoma). The level of angiotensin-induced hypertension was one and half times as high as blood pressure at rest. Induced hypertension was maintained for 30-60 minutes. In three cases of 5 primary osteosarcomas, induced hypertension resulted in the increase of tumor stain and/or vascularity angiographically, and chemotherapeutic effects were CR or PR. The six cases with soft-tissue sarcomas were 2 cases each of CR, PR, and NC. The decrease of relative tumor blood flow under the condition of angiotensin II-induced hypertension was detected in 5 cases of 6 soft-tissue sarcomas by 133Xe clearance method. In the case of rhabdomyosarcoma, the decrease of tumor stain and vascularity by induced hypertension was observed on angiogram. As the side effects accompanying induced hypertension, nausea and chest oppression were noted in 2 cases, respectively. In this study it was suggested that angiotensin II-induced hypertension chemotherapy was effective for osteosarcoma, but that it might be ineffective for soft-tissue sarcomas.

[Successful combination therapy of a metastatic Triton tumor in a 5-year-old boy]

A 5-year-old boy with a metastatic Triton tumor was treated with resection, local irradiation and an additional combination chemotherapy including Ifosfamide. One year after completion of the treatment the boy is now without a tumor and in excellent condition.

Phase II trial of ifosfamide in children with malignant solid tumors

Ifosfamide was given to 61 patients with malignant solid tumors diagnosed before the age of 21 years. In this phase II study, all patients received 1.6 g/m2/day X 5 iv over 15 minutes followed by mesna at a dose of 400 mg/m2 iv at 15 minutes and 4 and 6 hours after ifosfamide. Responses were observed in five of 15 patients with osteosarcoma, two of ten with neuroblastoma, two of six with Wilms' tumor, two of five with rhabdomyosarcoma, four of eight with other soft tissue sarcomas, one of one with retinoblastoma, one of two with germ cell tumors, one of one with B-cell lymphoma, and one of one with a primitive neuroectodermal tumor. Fifty-nine of 61 patients had received prior alkylating agent therapy which included cyclophosphamide, cisplatin, mechlorethamine, melphalan, or dacarbazine. Fourteen of 19 responses developed in patients whose tumors were resistant to treatment with cyclophosphamide. A patient with malignant Schwannoma who had received no prior chemotherapy developed a complete response which lasted 12 months. A patient with brain metastases of osteosarcoma has had complete response for greater than 2 years. Complete response was also observed in a patient with B-cell lymphoma. Toxicity consisted of mild to moderate nausea and vomiting, transient reversible myelosuppression, occasional elevation of serum BUN or creatinine, and transient neurotoxicity characterized by somnolence, confusion, weakness, tremor, hallucinations, or seizures. We conclude that ifosfamide is an important alkylating agent without apparent complete cross-resistance with cyclophosphamide, and as such should be further investigated for determination of its activity in patients with pediatric neoplasms and considered for incorporation into phase II-III trials for certain tumors.

[Formation of microfilament bundles in the tumor cell interphase nuclei of a rat neurinoma exposed to dimethyl sulfoxide]

The action of 15% dimethyl sulfoxide (DMSO) on the ultrastructure of the rat neurinoma cells (line NGUK-I) has been studied. The agent induced the formation of microfilament bundles in interphase nuclei after 30-60 min of treatment. The microfilament bundles revealed are suggested to be actin.

In vitro sensitivity of nitrosourea-induced neurogenic tumors to ACNU

The effect of ACNU on the in vitro viability of a methylnitrosourea-induced gliosarcoma (T9) and two ethylnitrosourea-induced brain tumors, TR-481 (a malignant neurinoma) and EB-679 (a glioma) was studied. T9 was highly sensitive to ACNU, demonstrating loss of cells following a 3 hour exposure time to 5 microgram/ml; TR-481 was sensitive to 40 microgram/ml of ACNU and EB-679 was highly resistant to 40 microgram/ml of ACNU. The in vitro sensitivity of the tumor cell lines to ACNU is: T 9 greater than TR-481 greater than EB-679. This data indicates that variability of response to both concentration and exposure time of ACNU of malignant brain tumor cells must be taken into consideration in planning in vitro and/or in vivo treatment of experimental brain tumors.

Malignant schwannoma--clinical characteristics, survival, and response to therapy

One hundred and sixty-five cases of malignant schwannoma were reviewed. Sixty-five (40%) of the patients had evidence of disseminated neurofibromatosis. Patients with neurofibromatosis were younger, had malignant schwannomas that were centrally rather than peripherally located, and had a shorter five-year survival (23%) than patients with solitary malignant schwannomas (47%). Histologically, tumors developing in patients with neurofibromatosis had a collagenous appearance, while tumors in patients without neurofibromatosis were undifferentiated and highly cellular. The clinical course of both groups of patients tended to be that of multiple local recurrences, although local recurrence had a more ominous prognosis in patients with neurofibromatosis. Chemotherapy responses in all these patients were extremely poor; however, the results of adjuvant therapy after surgery appeared encouraging. Fourteen patients (8.5%) had a malignant schwannoma in an area of prior radiation therapy and died of disease a median of 14 months after diagnosis. Malignant schwannoma should be considered in the differential diagnosis of tumors developing in areas previously treated with radiation.

The effect of nerve growth factor on undifferentiated glioma cells

Nerve growth factor (NGF) treatment of rats bearing implanted cells of an anaplastic glioma clone (F-98) led to a decreased tumor growth rate and increased survival time. Similar, but less pronounced, effects were observed if the cells were pretreated with NGF for 24 h before implantation. NGF also reduced the in vitro growth rate of F-98 and contributed to cellular maturation. Several well differentiated cell lines and clones were not visibly affected by NGF using the above parameters. We concluded that NGF has little or no effect on differentiated glioma cells, but significantly affects undifferentiated glioma cells by retarding their growth and inducing maturation.

Use of hyaluronidase in the central nervous system

Hyaluronidase, an enzyme which depolymerizes the mucopolysaccharide hyaluronic acid, appears to be tolerated by the human central nervous system and in the anterior chamber of the rabbit eye. Two patients with hydrocephalus and meningomyelocele had their condition curtailed by intraventricular injections of hyaluronidase, and in a third patient its use permitted delay of shunting. It was apparently effective in preventing a reaccumulation of cystic fluid in an intramedullary neurofibroma, and in reversing adverse effects of adhesive arachnoiditis of the spinal cord. Hylauronidase seems worthy of further investigation in disorders of the central nervous system.

Effect of levamisole on malignant experimental neurinoma grown subcutaneously in a young rat: brief communication

Levamisole, a drug that stimulates the immunologic defenses of the host, was tested on the experimental malignant neurinoma grown subcutaneously in young female inbred CDF rats in a 3-month trial. The drug resulted in prevention of tumor growth in 80% of the treated animals, whereas tumors grew in 100% of the controls. After discontinuation of the drug, none of the animals in the treated group showed evidence of tumor growth upon clinical and pathologic examination 1 month after drug treatment was terminated. Treated animals failed to show any side effects related to levamisole upon clinical and pathologic examination.