Atypical and anaplastic meningioma: outcomes in a population based study.

Atypical and anaplastic meningiomas (AAM) are aggressive tumors. This study is aimed at examining associations between patient and tumor-related factors and tumor-related death in patients with AAM. We conducted a population-based cohort study utilizing prospectively collected data from the Surveillance, Epidemiology, and End Results (SEER) database. Patients with diagnosis of AAM from 1973 to 2012 in the SEER database were included. Patients lacking clinical information were excluded. Multivariate analysis between patient and lesion characteristics, and AAM-related death was performed to adjust for confounding factors. We identified and included 522 patients in our study. Mean age at diagnosis was 60.8 ± 15.7 years. The majority of patients were White(73%), 15.5% Black, and 9.8% Asian. Average tumor size was 48.2 ± 20.3 mm. The tumor was locally confined in 57.1%, whereas it had intracranial extension in 29.3%, and extracranial extension in 8.8% of patients. The vast majority (94.8%) of tumors were supratentorial. Gross total resection (GTR) was documented in 65.5% of patients. Age at diagnosis (p = 0.001), tumor size (p = 0.003), surgery result (GTR vs. subtotal resection, p = 0.027), and radiation therapy (p = 0.2) were found to be significantly different between the comparison groups. In a multivariate proportional competing risk regression analysis age (HR 1.03, CI [1.01,1.04], p < 0.001), infratentorial location (HR 2.81, CI [1.20, 6.56], p = 0.017), tumor size (HR 1.01, CI [1.00,1.02], p = 0.032),and radiation treatment (HR 1.52, CI [1.11, 2.09], p = 0.01) were significantly associated with tumor-related death. The association of age at diagnosis, tumor size, location, and radiotherapy with overall survival in patients with AAM is demonstrated. The results provide a context for individualized treatment plans in patients with AAM. Additional studies focusing on issues such as the use of radiation and chemotherapy will clarify the best modality to achieve disease control.

Bone morphogenetic proteins inhibit the tumorigenic potential of human brain tumour-initiating cells.

Transformed, oncogenic precursors, possessing both defining neural-stem-cell properties and the ability to initiate intracerebral tumours, have been identified in human brain cancers. Here we report that bone morphogenetic proteins (BMPs), amongst which BMP4 elicits the strongest effect, trigger a significant reduction in the stem-like, tumour-initiating precursors of human glioblastomas (GBMs). Transient in vitro exposure to BMP4 abolishes the capacity of transplanted GBM cells to establish intracerebral GBMs. Most importantly, in vivo delivery of BMP4 effectively blocks the tumour growth and associated mortality that occur in 100% of mice after intracerebral grafting of human GBM cells. We demonstrate that BMPs activate their cognate receptors (BMPRs) and trigger the Smad signalling cascade in cells isolated from human glioblastomas (GBMs). This is followed by a reduction in proliferation, and increased expression of markers of neural differentiation, with no effect on cell viability. The concomitant reduction in clonogenic ability, in the size of the CD133+ population and in the growth kinetics of GBM cells indicates that BMP4 reduces the tumour-initiating cell pool of GBMs. These findings show that the BMP-BMPR signalling system--which controls the activity of normal brain stem cells--may also act as a key inhibitory regulator of tumour-initiating, stem-like cells from GBMs and the results also identify BMP4 as a novel, non-cytotoxic therapeutic effector, which may be used to prevent growth and recurrence of GBMs in humans.

Inhibition of tumor angiogenesis mediated by cartilage.

Capillary proliferation induced by tumor is shown to be inhibited by neonatal scapular cartilage. Using the rabbit cornea as an assay, the cartilage implant decreased the rate of capillary growth, induced by tumor, by an average of 75%. Vascularization was prevented completely in 28% of tumors. The inhibitory effect of small cartilage implants operates over distances of up to 2.0 mm and displays a gradient from the cartilage source. The experiments suggest that the cartilage inhibitor does not antagonize tumor angiogenesis factor, but appears to inhibit capillary proliferation directly. The inhibitory material does not elicit an inflammatory response in either the rabbit cornea or in the chick chorioallantoic membrane. Thus with further purification, it may prove useful as a means of maintining tumor dormancy by "antiangiogenesis."

Isolations of a cartilage factor that inhibits tumor neovascularization.

A cartilage fraction isolated by guanidine extraction and purified by affinity chromatography inhibits tumor-induced vascular proliferation and consequently restricts tumor growth. This fraction contains several different proteins; the major one has a molecular weight of about 16,000. The fraction strongly inhibits protease activity.

Use of an anti-viral drug, Ribavirin, as an anti-glioblastoma therapeutic.

The median survival for glioblastoma patients is ~15 months despite aggressive surgery and radio-chemotherapy approaches. Thus, developing new therapeutics is necessary to improve the treatment of these invasive brain tumors, which are known to show high levels of the eukaryotic initiation factor, eIF4E, a potent oncogene. Ribavirin, the only clinically approved drug known to target eIF4E, is an anti-viral molecule currently used in hepatitis C treatment. Here, we report the effect of ribavirin on proliferation, cell cycle, cell death and migration of several human and murine glioma cell lines, as well as human glioblastoma stem-like cells, in vitro. In addition, we tested ribavirin efficacy in vivo, alone and in combination with temozolomide and radiation. Our work showed that ribavirin inhibits glioma cell growth and migration, and increases cell cycle arrest and cell death, potentially through modulation of the eIF4E, EZH2 and ERK pathways. We also demonstrate that ribavirin treatment in combination with temozolomide or irradiation increases cell death in glioma cells. Finally and most importantly, ribavirin treatment in vivo significantly enhances chemo-radiotherapy efficacy and improves survival of rats and mice orthotopically implanted with gliosarcoma tumors or glioma stem-like cells, respectively. On the basis of these results, we propose that ribavirin represents a new therapeutic option for glioblastoma patients as an enhancer of the cytotoxic effects of temozolomide and radiotherapy.

Angiogenesis inhibition by minocycline.

We describe a new inhibitor of angiogenesis, minocycline, a semisynthetic tetracycline antimicrobial with anticollagenase properties. Minocycline was incorporated into controlled release polymers and tested in the rabbit cornea against neovascularization in the presence of the VX2 carcinoma. Inhibition by minocycline was shown to be comparable to that of the combination of heparin and cortisone, a potent inhibitor of angiogenesis. Minocycline decreased tumor-induced angiogenesis by a factor of 4.5, 4.4, and 2.9 at 7, 14, and 21 days, respectively. At the end of the experiment, whereas the corneas with empty polymers had large, invasive, exophytic tumors, none of the corneas with minocycline had such vascular masses. Recently, studies of agents that disrupt collagen synthesis and deposition have yielded several new angiogenesis inhibitors. We suggest that investigation of agents that disrupt collagenolysis may similarly identify other angiogenesis inhibitors and further clarify the mechanisms of angiogenesis.

Controlled delivery of 1,3-bis(2-chloroethyl)-1-nitrosourea from ethylene-vinyl acetate copolymer.

1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU) has been found to be an effective chemotherapeutic agent against brain tumors. However, because it has a very short half-life in plasma, the exposure of neoplastic cells to BCNU is very brief. The delivery of BCNU may be enhanced by using controlled release polymers. We measured the release of BCNU from ethylene-vinyl acetate copolymer (EVAc) into blood, phosphate buffer, and brain tissue. BCNU-EVAc cylinders that weighed 60 mg were implanted in the peritoneum of rats, and BCNU was detected in blood for 6 days. Studies carried out in vitro showed that BCNU was released from EVAc at a decreasing rate for 195 h. BCNU-EVAc cylinders that weighed 15 mg were implanted either intracranially (i.c.) or i.p. in Fischer 344 rats. Controlled release of BCNU from the i.c. BCNU-EVAc implants was observed over 9 days, with peak drug levels of 49.6 micrograms/g of brain tissue in the implanted hemisphere. The BCNU levels in the contralateral hemisphere and the peripheral circulation were much lower and were detectable for only 1 day. By contrast, peak BCNU levels in the brain from the i.p. BCNU-EVAc implants were 2.7-3.0 micrograms/g for only 12 h, accompanied by peak BCNU levels in blood of 1.0 micrograms/ml tapering over 1 day. These results demonstrate the controlled release of intact BCNU from EVAc in vitro and in vivo. Furthermore, the i.c. implants resulted in localized, prolonged, high levels of the drug in the implanted hemisphere. Hence, the i.c. controlled delivery of BCNU may be more efficacious for the treatment of localized brain tumors.

Covalent coupling of methotrexate to dextran enhances the penetration of cytotoxicity into a tissue-like matrix.

For antitumor agents introduced directly into the intracranial space, the extent of penetration into tissue, and hence the effectiveness of therapy, depends on the rate of drug elimination from the tissue. To test the hypothesis that slowly eliminated agents would penetrate further through tissues, methotrexate (MTX)-dextran conjugates were produced by covalently linking MTX to dextran through a short-lived ester bond (MTX-ester-dextran; t1/2 approximately 3 days in buffered saline) and a longer-lived amide bond (MTX-amide-dextran; t1/2 > 20 days in buffered saline). The ability of these agents to kill cells and to penetrate through tissue was evaluated using: (a) human brain tumor (H80) cells in a standard format; (b) H80 cells in a novel three-dimensional format that mimics many characteristics of intracranial tumors; and (c) 9L gliosarcoma in the rat brain. Penetration into three-dimensional tissue-like matrices was performed by suspending H80 cells in agarose gels within a hollow fiber that was permeable to MTX but not dextran and injecting MTX or MTX-dextran conjugates into one end of the fiber. The cytotoxicity of MTX-ester-dextran and MTX-amide-dextran against H80 was equivalent to unmodified MTX (50% inhibitory concentration, approximately 0.01 microgram/ml). When released from a biodegradable polyanhydride polymer matrix, MTX and MTX-dextran conjugates retained their ability to inhibit dihydrofolate reductase activity. When MTX or MTX-dextran was diffused into the three-dimensional tumor cell matrix for 10 days, cytotoxic activity penetrated > 2 cm for MTX-amide-dextran and approximately 1 cm for MTX or MTX-ester-dextran; this enhanced penetration correlated with the stability of the MTX-dextran linkage. Intracranial polymeric delivery of MTX or MTX-amide-dextran to rats with intracranial 9L gliosarcoma produced modest but significant increases in survival; conjugation of MTX to dextran appeared to shift the dose-response curve to a lower dosage.

Prolonged tumor dormancy by prevention of neovascularization in the vitreous.

Tumors release a diffusible substance that stimulates neovascularization. To study the neovascularization that occurs in diabetic retinopathy, we implanted V2 carcinomas and mouse ependymoblastomas into the vitreous of experimental animals. In the vitreous, unlike previous sites, the tumors failed to stimulate neovascularization. They grew for weeks as small, unvascularized, three-dimensional aggregates of cells. Explosive growth into a large, vascularized mass occurred when the avascular tumors reached the retinal surface. The vitreous proved to be a valuable model for observing the in vivo growth of small, solid tumors. Xenografts survived for months without evidence of immune rejection. The consequence of the prolonged avascular state is the restriction of tumor size. The normal vitreous may act to inhibit capillary proliferation. An understanding of the mechanism for maintaining the avascular state may lead to therapeutic blockade of neovascularization. This would be important in the management of diabetic retinopathy and neoplasia.

Interstitial chemotherapy of the 9L gliosarcoma: controlled release polymers for drug delivery in the brain.

The administration of drugs directly into the central nervous system using polymers as drug carriers may improve the treatment of malignant brain tumors. In this study, the effect of the interstitial, localized delivery of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) incorporated into controlled release polymers implanted adjacent to the 9L gliosarcoma was assessed in s.c. and intracranial (i.c.) models. In the s.c. experiment, the 9L gliosarcoma was implanted in the flank of rats and subsequently treated with BCNU either (a) delivered in controlled release polymers inserted adjacent to the tumor or (b) administered systemically by i.p. injections or by controlled release polymers inserted at a site distant from the tumor. The interstitial release of BCNU adjacent to the tumor in the flank resulted in a significant tumor growth delay of 16.3 days, as compared to a growth delay of 9.3 and 11.2 days obtained with the systemic administration of BCNU. In the i.c. experiment, the 9L gliosarcoma was implanted in the brain of Fischer 344 rats and treated either (a) with controlled release polymers containing BCNU inserted into the brain or (b) with the systemic i.p. administration of BCNU. The interstitial release of BCNU in the brain resulted in a significant 5.4- to 7.3-fold increased survival, compared with a 2.4-fold increased survival after the systemic administration of the same dose of BCNU. The two groups with i.c. tumors treated interstitially had 17 and 42% cures, but no long-term cures were obtained in the group treated with systemic therapy. The localized, controlled delivery of chemotherapeutic agents in the s.c. tissues and in the brain via polymeric carriers may be more effective than standard systemic chemotherapy. This approach could be used to deliver a wide variety of agents into the central nervous system to treat diverse neuropathological conditions which remain refractory to systemic therapy.

O6-benzylguanine potentiates the antitumor effect of locally delivered carmustine against an intracranial rat glioma.

Local delivery of carmustine (BCNU) via biodegradable polymers prolongs survival against experimental brain tumors and in human clinical trials. O6-benzylguanine (O6-BG), a potent inhibitor of the DNA repair protein, O6-alkylguanine-DNA alkyltransferase (AGT), has been shown to reduce nitrosourea resistance and, thus, enhance the efficacy of systemic BCNU therapy in a variety of tumor models. In this report, we demonstrate that O6-BG can potentiate the activity of BCNU delivered intracranially via polymers in rats challenged with a lethal brain tumor. Fischer 344 rats received a lethal intracranial challenge of 100,000 F98 glioma cells (F98 cells have significant AGT activity, 328 fmol/mg protein). Five days later, animals receiving an i.p. injection of O6-BG (50 mg/kg) 2 h prior to BCNU polymer (3.8% BCNU by weight) implantation had significantly improved survival (n = 7; median survival, 34 days) over animals receiving either O6-BG alone (n = 7; median survival, 22 days; P = 0.0002) or BCNU polymer alone (n = 8; median survival, 25 days; P = 0.0001). Median survival for the control group (n = 8) was 23.5 days. Moreover, there was no physical, behavioral, or pathological evidence of treatment-related toxicity. These findings suggest that O6-BG can potentiate the effects of interstitially delivered BCNU and, for tumors expressing significant AGT, may be necessary for the BCNU to provide a meaningful therapeutic benefit. Given the clinical use of BCNU polymers against malignant gliomas, concurrent treatment with O6-BG may provide an important addition to our therapeutic armamentarium.

Paracrine immunotherapy with interleukin-2 and local chemotherapy is synergistic in the treatment of experimental brain tumors.

Potent immune responses against malignant brain tumors can be elicited by paracrine intracranial (i.c.) immunotherapy with interleukin (IL)-2. Additionally, i.c. delivery of carmustine via biodegradable polymers has been shown to significantly prolong survival in both animal models and clinical trials. In this study, we show that the combination of paracrine immunotherapy, with nonreplicating genetically engineered tumor cells that produce IL-2, and local delivery of chemotherapy by biodegradable polymers prolongs survival in a synergistic manner in mice challenged intracranially with a lethal murine brain tumor. Animals receiving IL-2-transduced cells and polymers containing 10% 1,3-bis(2-chloroethyl)-1-nitrosourea had significantly improved survival compared with animals receiving IL-2-transduced cells or 10% 1,3-bis(2-chloroethyl)-1-nitrosourea alone. Median survival for the control group was 19 days. Survival in animals receiving IL-2-transduced cells and 1% carboplatin-containing polymers was also significantly improved compared with either therapy alone. Histopathological examination on day 14 of animals receiving combination treatment showed rare degenerating tumor cells. In addition to tissue necrosis surrounding the polymer, a marked inflammatory reaction was observed. In long-term survivors (all animals receiving combination treatment), no tumor was observed and the inflammatory reaction was completely resolved. The brains of animals receiving combination therapy showed both tissue necrosis due to local chemotherapy and strong inflammation due to paracrine immunotherapy. The demonstration of synergy between paracrine IL-2 and local i.c. delivery of antineoplastic drugs is novel and may provide a combined treatment strategy for use against both primary and metastatic i.c. tumors.

Transforming growth factor-alpha-Pseudomonas exotoxin fusion protein (TGF-alpha-PE38) treatment of subcutaneous and intracranial human glioma and medulloblastoma xenografts in athymic mice.

Epidermal growth factor receptor (EGFR) is amplified or overexpressed in many malignant gliomas and other primary brain tumors but is low or undetectable in normal brain. In the present study, this differential expression has been exploited for targeted brain tumor therapy using a TGF-alpha-Pseudomonas exotoxin recombinant toxin, TGF-alpha-PE38. In vitro experiments demonstrate that the cytotoxicity of this fusion protein is primarily determined by tumor EGFR expression and that TGF-alpha-PE38 cytotoxicity is abolished by pretreatment with excess epidermal growth factor. Treatment with i.p. TGF-alpha-PE38 in nude mice bearing glioblastoma or medulloblastoma s.c. xenografts produced tumor regression and growth delay. For intracranial xenograft implants treated with i.p. TGF-alpha-PE38, significant increases in median survival were noted only for tumors with the highest EGFR expression. However, intracranial tumors treated with a single intratumoral injection of TGF-alpha-PE38 showed increased survival in all xenografts tested. These results indicate that TGF-alpha-PE38 is active against primary human brain tumors ranging from moderate to high EGFR expression. For intracranial tumors, however, the higher survival rates produced by intracranial injection of TGF-alpha-PE38 than by continuous i.p. administration suggest that increased drug clearance or impaired drug delivery reduces the efficacy of systemic TGF-alpha-PE38. Direct delivery of TGF-alpha-PE38 into brain tumors by controlled-release biodegradable polymers or intratumoral implanted catheters, or intrathecal administration into the colony stimulating factor of patients with leptomeningeal metastasis, may represent clinically useful applications of recombinant toxin therapy in tumors with high EGFR expression.

In vivo 31P nuclear magnetic resonance spectroscopy of subcutaneous 9L gliosarcoma: effects of tumor growth and treatment with 1,3-bis(2-chloroethyl)-1-nitrosourea on tumor bioenergetics and histology.

In vivo 31P nuclear magnetic resonance spectroscopy was used to examine the bioenergetics of the rat 9L gliosarcoma during untreated growth and in response to chemotherapy with 1,3-bis(2-chloroethyl)-1-nitrosourea. Tumor growth was associated with a decline in the phosphocreatine and nucleoside triphosphate resonances, consistent with an increase in tumor hypoxia during untreated growth. Following chemotherapy with 1,3-bis(2-chloroethyl)-1-nitrosourea (10 mg/kg), tumor levels of phosphocreatine and nucleoside triphosphate rebounded while the level of inorganic phosphate in the tumor declined. Histological comparison of treated and untreated tumor sections 4 days posttreatment showed that the treated tumor had a lower proportion of necrotic cells, a higher proportion of viable cells, and a 5-fold higher level of interstitial space than the control tumor.

Local delivery of chemotherapy and concurrent external beam radiotherapy prolongs survival in metastatic brain tumor models.

Local chemotherapy with biodegradable polymers prolongs survival with minimal morbidity in patients with intracranial high-grade gliomas. However, use of local chemotherapy for metastatic brain tumors has not been defined. We studied the safety and the efficacy of locally delivered chemotherapy with and without concurrent radiation therapy in treating tumors that frequently metastasize to the brain. The chemotherapeutic agents 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), carboplatin, and camptothecin were incorporated into controlled-release polymers and tested individually against intracranial challenges with one of four tumors (lung carcinoma, renal cell carcinoma, colon carcinoma, and melanoma). For each combination of drug and tumor type, four groups were tested: (a) empty polymer (no drug); (b) external beam radiotherapy (XRT) alone; (c) local chemotherapy from biodegradable polymer alone; and (d) local chemotherapy and XRT together. Polymers were implanted 5 days after tumor inoculation; XRT was given on days 7-9 (300 cGy/day). BCNU and XRT together were effective against all four tumors. BCNU polymer alone significantly prolonged survival in mice with intracranial melanoma or renal cell carcinoma. Carboplatin alone was effective against both melanoma and colon carcinoma and in combination with XRT against colon and renal cell carcinomas. Camptothecin was effective only with XRT against melanoma. These studies demonstrate that local delivery of chemotherapy with concurrent radiation therapy is safe and can significantly prolong survival in models of common intracranial metastatic tumors. Concurrent use of local chemotherapy with standard XRT appears to be more effective than either treatment alone. Local chemotherapy may also be of benefit to patients who have previously received maximal cranial irradiation but suffer an intracranial recurrence.

Interstitial taxol delivered from a biodegradable polymer implant against experimental malignant glioma.

Taxol is a novel antitumor agent with demonstrated efficacy against ovarian, breast, and non-small cell lung cancers in Phase II clinical trials, but which has been shown not to cross the blood-brain barrier. To adapt taxol as a therapy for brain tumors, we have incorporated it into a biodegradable polyanhydride matrix for intracranial implantation and evaluated this formulation in a rat model of malignant glioma. Fischer 344 rats bearing intracranial 9L glioma tumors were treated with 10 mg poly[bis(p-carboxyphenoxy)propane-sebacic acid] (20:80) copolymer discs, containing 20-40% taxol by weight, 5 days after tumor implantation. The taxol-loaded polymers doubled (38 days, 40% taxol loading, P < 0.02) to tripled (61.5 days, 20% taxol loading, P < 0.001) the median survival of rats bearing tumor relative to control rats (19.5 days). Drug loadings of 20-40% taxol by weight released intact taxol for up to 1000 h in vitro. In rats followed up to 30 days postimplant, the polymer maintained a taxol concentration of 75-125 ng taxol/mg brain tissue (100-150 microM taxol) within a 1-3-mm radius of the disc. At points more distant from the disc (up to 8 mm away, the size limit of the rat brain), the polymer maintained a taxol concentration of greater than 4 ng taxol/mg brain tissue (5 microM). We conclude that taxol shows promise as a therapy for malignant glioma when delivered interstitially from a biodegradable polymer.

Pharmacokinetics of interstitial delivery of carmustine, 4-hydroperoxycyclophosphamide, and paclitaxel from a biodegradable polymer implant in the monkey brain.

Polymeric interstitial chemotherapy increases survival of humans with recurrent gliomas and animals with transplanted tumors in the brain, but the relationship between rates of drug release from polymer implants and drug concentration in brain tissue is unknown. This work presents a pharmacokinetic framework for application of this new modality of chemotherapy delivery in primates. Either [3H]carmustine, 4-hydroperoxycyclophosphamide (4-HC), or paclitaxel was encapsulated in a polyanhydride pellet (28-41 microCi/animal, 40 mg/animal), which was implanted intracranially in cynomolgus monkeys (Macaca fascicularis); (n = 17) for up to 30 days. Drug concentrations in the brain, blood, and cerebrospinal fluid were measured by quantitative autoradiography, TLC, and scintillation counting. High drug concentrations (0.5-3.5 mM for carmustine, 0.3-0.4 mM for 4-HC, and 0.2-1.0 mM for paclitaxel) were measured within the first 3 mm from the polymer implant; significant (0.4 microM for carmustine, 3 microM for 4-HC, and 0.6 microM for paclitaxel) concentrations were measured up to approximately 5 cm from the implant as long as 30 days after implantation. Pharmacokinetic analysis indicated that tissue exposure to carmustine area under concentration-time curve achieved by polymeric delivery was 4-1200 times higher than that produced by i.v. administration of a higher dose.

Squalamine inhibits angiogenesis and solid tumor growth in vivo and perturbs embryonic vasculature.

The novel aminosterol, squalamine, inhibits angiogenesis and tumor growth in multiple animal models. This effect is mediated, at least in part, by blocking mitogen-induced proliferation and migration of endothelial cells, thus preventing neovascularization of the tumor. Squalamine has no observable effect on unstimulated endothelial cells, is not directly cytotoxic to tumor cells, does not alter mitogen production by tumor cells, and has no obvious effects on the growth of newborn vertebrates. Squalamine was also found to have remarkable effects on the primitive vascular bed of the chick chorioallantoic membrane, which has striking similarities to tumor capillaries. Squalamine may thus be well suited for treatment of tumors and other diseases characterized by neovascularization in humans.

New directions in CNS drug delivery.

This commentary expands on the above article in 2 ways. First, it provides more recent information on polymer-based drug delivery systems. Second, it discusses experimental systems that may be clinically viable in the future such as prodrugs, cell-polymer transplants and gene transplants.