Malignant glioma: should chemotherapy be overthrown by experimental treatments?

Synthetic Cannabinoids Induce Autophagy and Mitochondrial Apoptotic Pathways in Human Glioblastoma Cells Independently of Deficiency in TP53 or PTEN Tumor Suppressors

Simple Summary

Glioblastomas (GBMs) are aggressive brain tumors with frequent genetic defects in TP53 and PTEN tumor suppressor genes, which render tumors refractory to standard chemotherapeutics. Natural and synthetic cannabinoids showed antitumor activity in glioma cells and animal glioma models. Due to differences in the expression of cannabinoid type 2 receptors (CB2), which are abundant in GBMs but absent from a healthy brain, we tested synthetic cannabinoids for their ability to kill numerous glioma cells. We performed multiple biochemical analyses to determine which cell death pathways are activated in human glioma cells. We demonstrate high susceptibility of human glioblastoma cells to synthetic cannabinoids, despite genetic defects contributing to apoptosis resistance, which makes cannabinoids promising anti-glioma therapeutics.

Abstract

Glioblastomas (GBMs) are aggressive brain tumors with frequent genetic alterations in TP53 and PTEN tumor suppressor genes rendering resistance to standard chemotherapeutics. Cannabinoid type 1 and 2 (CB1/CB2) receptor expression in GBMs and antitumor activity of cannabinoids in glioma cells and animal models, raised promises for a targeted treatment of these tumors. The susceptibility of human glioma cells to CB2-agonists and their mechanism of action are not fully elucidated. We determined CB1 and CB2 expression in 14 low-grade and 21 high-grade tumor biopsies, GBM-derived primary cultures and established cell lines. The non-selective CB receptor agonist WIN55,212-2 (but not its inactive enantiomer) or the CB2-selective agonist JWH133 induced apoptosis in patient-derived glioma cultures and five established glioma cell lines despite p53 and/or PTEN deficiency. Growth inhibitory efficacy of cannabinoids correlated with CB1/CB2 expression (EC₅₀ WIN55,212-2: 7.36–15.70 µM, JWH133: 12.15–143.20 µM). Treatment with WIN55,212-2 or JWH133 led to activation of the apoptotic mitochondrial pathway and DNA fragmentation. Synthetic cannabinoid action was associated with the induction of autophagy and knockdown of autophagy genes augmented cannabinoid-induced apoptotic cell death. The high susceptibility of human glioblastoma cells to synthetic cannabinoids, despite genetic defects contributing to apoptosis resistance, makes cannabinoids promising anti-glioma therapeutics.

Case Report: Clinical Outcome and Image Response of Two Patients With Secondary High-Grade Glioma Treated With Chemoradiation, PCV, and Cannabidiol

We describe two patients with a confirmed diagnosis of high-grade gliomas (grades III/IV), both presenting with O6-methylguanine-DNA methyltransferase (MGMT) methylated and isocitrate dehydrogenase (IDH-1) mutated who, after subtotal resection, were submitted to chemoradiation and followed by PCV, a multiple drug regimen (procarbazine, lomustine, and vincristine) associated with cannabidiol (CBD). Both patients presented with satisfactory clinical and imaging responses at periodic evaluations. Immediately after chemoradiation therapy, one of the patients presented with an exacerbated and precocious pseudoprogression (PSD) assessed by magnetic resonance imaging (MRI), which was resolved in a short period. The other patient presented with a marked remission of altered areas compared with the post-operative scans as assessed by MRI. Such aspects are not commonly observed in patients only treated with conventional modalities. This observation might highlight the potential effect of CBD to increase PSD or improve chemoradiation responses that impact survival. Further investigation with more patients and critical molecular analyses should be performed.

Preradiation Chemotherapy with VM-26 and CCNU in Patients with Glioblastoma Multiforme

Aims and Background

The objective of the study was to evaluate the efficacy of combined chemoradiation in patients with newly diagnosed glioblastoma multiforme. The main end points were time to progression and overall survival.

Methods

Thirty-one patients with glioblastoma multiforme underwent surgery whenever possible and then received intravenous VM26 (120 mg/m2) and oral CCNU (120 mg/m2) for three cycles followed by radiotherapy (60 Gy).

Results

Surgery consisted of a complete resection in 39% of patients, partial resection in 35% and a biopsy in 26%. Sixteen patients had clinical or radiological evidence of progression during or after chemotherapy. Hematologic toxicity was mild. Forty-five percent of patients received the scheduled dose of radiation. The outcome was disappointing, with a median time to progression of 18 weeks and median survival of 37.17 weeks.

Conclusions

The survival of patients with glioblastoma multiforme remains disappointing. Multimodal therapy does not seem to modify the evolution of the tumor. Stratification according to prognostic factors might detect a potential benefit of other therapeutic approaches.

LRIG1 enhances chemosensitivity by modulating BCL-2 expression and receptor tyrosine kinase signaling in glioma cells

PURPOSE

Leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) are an inhibitor of receptor tyrosine kinases (RTKs) that was discovered in recent years, and many studies showed that LRIG1 is a tumor suppressor gene and may be related to tumor drug resistance. In this study, we explored whether LRIG1 protein expression can improve the chemosensitivity of glioma cells and what was its mechanism.

MATERIALS AND METHODS

We collected 93 cases of glioma tissues and detected the expression of LRIG1 and BCL-2. We constructed a multidrug resistance cell line U251/multidrug resistance (MDR) and examined the change of LRIG1 and BCL-2 at mRNA and protein expression levels. LRIG1 expression was upregulated in U251/MDR cells and we detected the change of multidrug resistance. Meanwhile, we changed the expression of LRIG1 and BCL-2 and explored the relationship between LRIG1 and BCL-2. Finally, we also explored the relationship between LRIG1 and RTKs.

RESULTS

LRIG1 was negatively correlated with BCL-2 expression in glioma tissue and U251/MDR cells, and upregulation of LRIG1 can enhance chemosensitivity and inhibit BCL-2 expression. Furthermore, LRIG1 was negatively correlated with RTKs in U251/MDR cells.

CONCLUSION

These results demonstrated that LRIG1 can improve chemosensitivity by modulating BCL-2 expression and RTK signaling in glioma cells.

Transforming growth factor-beta and its implication in the malignancy of gliomas

Malignant gliomas are the most common type of primary malignant brain tumors. They are characterized by enhanced growing capabilities, neoangiogenic proliferation, and extensive infiltration of the brain parenchyma, which make their complete surgical resection impossible. Together with transient and refractory responses to standard therapy, these aggressive neoplasms are incurable and present a median survival of 12 to 14 months. Transforming growth factor-beta (TGF-β) is a pleiotropic cytokine of which two of the three isoforms expressed in humans have been shown to be overexpressed proportionally to the histologic grade of glioma malignancy. The increase of chromosomal aberrations and genetic mutations observed in glioma cells turns TGF-β into an oncogene. For that reason, it plays critical roles in glioma progression through induction of several genes implicated in many carcinogenic processes such as proliferation, angiogenesis, and invasion. Consequently, investigators have begun developing innovative therapeutics targeting this growth factor or its signaling pathway in an attempt to hinder TGF-β's appalling effects in order to refine the treatment of malignant gliomas and improve their prognosis. In this paper, we extensively review the TGF-β-induced oncogenic pathways and discuss the diverse new molecules targeting this growth factor.

Magnetic nanoparticles for tumor imaging and therapy: a so-called theranostic system

In this review, we discussed the establishment of a so-called "theranostic" system by instituting the basic principles including the use of: [1] magnetic iron oxide nanoparticles (MION)-based drug carrier; [2] intra-arterial (I.A.) magnetic targeting; [3] macromolecular drugs with unmatched therapeutic potency and a repetitive reaction mechanism; [4] cell-penetrating peptide-mediated cellular drug uptake; and [5] heparin/protamine-regulated prodrug protection and tumor-specific drug re-activation into one single drug delivery system to overcome all possible obstacles, thereby achieving a potentially non-invasive, magnetic resonance imaging-guided, clinically enabled yet minimally toxic brain tumor drug therapy. By applying a topography-optimized I.A. magnetic targeting to dodge rapid organ clearance of the carrier during its first passage into the circulation, tumor capture of MION was enriched by >350 folds over that by conventional passive enhanced permeability and retention targeting. By adopting the prodrug strategy, we observed by far the first experimental success in a rat model of delivering micro-gram quantity of the large β-galactosidase model protein selectively into a brain tumor but not to the ipsi- or contra-lateral normal brain regions. With the therapeutic regimens of most toxin/siRNA drugs to fully (>99.9%) eradicate a tumor being in the nano-molar range, the prospects of reaching this threshold become practically accomplishable.

Does extent of resection impact survival in patients bearing glioblastoma?

BACKGROUND

The impact of malignant glioma resection on survival is still a matter of controversy. The lack of well-designed prospective studies as well as control of all factors in retrospective studies plays an important role in this debate. Amongst some of these uncontrolled factors, are the inclusion of different histological grades, the lack of objective methods to estimate the extent of resection and unspecified delays in post-operative imaging.

METHODS

We retrospectively reviewed 126 consecutive patients with glioblastoma, operated on by the senior authors at the Centre Hospitalier Universitaire de Sherbrooke, who met the following criteria: >18 years of age, newly diagnosed glioblastoma, pre-operative magnetic resonance imaging (MRI) within 2 weeks prior to surgery, and a post-operative MRI within 72 hours after surgery. Extent of tumour resection was calculated using pre and post-operative tumour delimitation on gadolinium-enhanced T1 MRI in a volumetric analysis.

RESULTS

Applying stringent specific inclusion criteria, 126 patients were retained in the analysis. The median overall survival was 271 days and the median extent of resection was 65%. Patients with more than 90% of tumour resection had a significantly better outcome, improving median survival from 225 to 519 days (P=0.006). Other factors that significantly improved survival were the use of radiotherapy, the number of regimens and type of chemotherapy used.

CONCLUSION

A more aggressive approach combining maximal safe resection and use of salvage chemotherapy seems to confer a survival advantage for glioblastoma patients.

CCL5, CCR1 and CCR5 in murine glioblastoma: immune cell infiltration and survival rates are not dependent on individual expression of either CCR1 or CCR5

Glioblastoma multiforme (GBM) is the most malignant brain tumor. Microglia/macrophages are found within human GBM where they likely promote tumor progression. We report that CCL5, CCR1, and CCR5 are expressed in glioblastoma. Individual deletion of CCR1 or CCR5 had little to no effect on survival of tumor bearing mice, or numbers of glioblastoma-infiltrated microglia/macrophages or lymphocytes. CCL5 promoted in vitro migration of wild type, CCR1- or CCR5-deficient microglia/macrophages that was blocked by the dual CCR1/CCR5 antagonist, Met-CCL5. These data suggest that CCL5 functions within the glioblastoma microenvironment through CCR1 and CCR5 in a redundant manner.

Temozolomide: The evidence for its therapeutic efficacy in malignant astrocytomas

Introduction:

Malignant gliomas are a heterogeneous group of primary central nervous system neoplasms that represent less than 2% of all cancers yet carry a significant burden to society. They are frequently associated with considerable and progressive neurological disability and are ultimately intractable to all forms of treatment. Temozolomide (TMZ) is a new second generation DNA alkylating agent that has become part of malignant astrocytoma management paradigms because of its proven efficacy, ease of administration, and favorable toxicity profile.

Aims:

To review the role of TMZ in the management of malignant astrocytomas (World Health Organization grades III and IV) including newly diagnosed (n) and recurrent (r) anaplastic astrocytomas (AA) and glioblastomas.

Evidence review:

A series of pivotal clinical trials have established a role for TMZ in the treatment of malignant astrocytomas. A large phase II trial examining the role of TMZ in rAA showed a response rate of 35%, and a 6-month progression-free survival of 46%. This led to the accelerated approval of TMZ by the FDA and the EU for the treatment of rAA. Evidence for a role of TMZ in nAA is currently limited but research is ongoing in this area. The role of TMZ in the management of glioblastoma at the time of recurrence (rGBM) is less impressive but evidence for its activity was demonstrated in two large phase II trials that led to the approval of TMZ for this indication in Europe and Canada but not in the US. A recent large prospective randomized phase III trial showed that the addition of TMZ during and after radiation therapy (RT) in newly diagnosed (nGBM) patients prolonged median overall survival by 2.5 months; perhaps more importantly, the 2-year survival rate for patients receiving TMZ and RT was 26% compared with 10% for those receiving RT alone. Concurrent TMZ with RT followed by adjuvant TMZ has become the standard of care for nGBM patients. Based on the evidence presented in this trial, TMZ received approval from the FDA and the EU for patients with nGBM in 2005.

Place in therapy:

There is evidence to support the use of TMZ for the following diseases in the order of most to least convincing: nGBM, rAA, rGBM, and nAA. This order may quickly change as more trials are being designed and implemented, particularly with novel TMZ dosing schedules.

Tamoxifen alleviates irradiation-induced brain injury by attenuating microglial inflammatory response in vitro and in vivo

Irradiation-induced brain injury, leading to cognitive impairment several months to years after whole brain irradiation (WBI) therapy, is a common health problem in patients with primary or metastatic brain tumor and greatly impairs quality of life for tumor survivors. Recently, it has been demonstrated that a rapid and sustained increase in activated microglia following WBI led to a chronic inflammatory response and a corresponding decrease in hippocampal neurogenesis. Tamoxifen, serving as a radiosensitizer and a useful agent in combination therapy of glioma, has been found to exert anti-inflammatory response both in cultured microglial cells and in a spinal cord injury model. In the present study, we investigated whether tamoxifen alleviated inflammatory damage seen in the irradiated microglia in vitro and in the irradiated brain. Irradiating BV-2 cells (a murine microglial cell line) with various radiation doses (2-10 Gy) led to the increase in IL-1 beta and TNF-alpha expression determined by ELISA, and the conditioned culture medium of irradiated microglia with 10 Gy radiation dose initiated astroglial activation and decreased the number of neuronal cells in vitro. Incubation BV-2 cells with tamoxifen (1 microM) for 45 min significantly inhibited the radiation-induced microglial inflammatory response. In the irradiated brain, WBI induced the breakdown of the blood-brain barrier permeability at day 1 post irradiation and tissue edema formation at day 3 post-radiation. Furthermore, WBI led to microglial activation and reactive astrogliosis in the cerebral cortex and neuronal apoptosis in the CA1 hippocampus at day 3 post-radiation. Tamoxifen administration (i.p., 5 mg/kg) immediately post radiation reduced the irradiation-induced brain damage after WBI. Taken together, these data support that tamoxifen can decrease the irradiation-induced brain damage via attenuating the microglial inflammatory response.

Real-time monitoring of gadolinium diethylenetriamine penta-acetic acid during osmotic blood-brain barrier disruption using magnetic resonance imaging in normal wistar rats

OBJECTIVE

Treatment of malignant gliomas is hampered by several factors, one of which is the blood-brain barrier (BBB). Thus, innovative strategies to cross the BBB have been developed, such as the BBB disruption procedure. Although it has been studied extensively, details regarding the physiology of the procedure remain obscure. This study was undertaken to clarify these issues.

METHODS

Forty Wistar rats were imaged with a 7T animal magnetic resonance imaging scanner in dynamic acquisitions during BBB disruption. Gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) was injected to visualize and characterize the permeability of the BBB at different time points after disruption. The concentration of Gd-DTPA in the brain parenchyma was determined as a function of time after injection.

RESULTS

A typical pattern of signal change as a function of time was observed in the treated hemisphere of all animals. Initially, a slight signal decrease was observed in T1-weighted images followed by a strong increase corresponding to the injection of Gd-DTPA. Two different mechanisms seemed responsible for the distribution of Gd-DTPA within the parenchyma: 1) a direct diffuse increase in capillary permeability, and 2) a diffusion process in the interstitial compartment. Initial results showed that the barrier opens immediately after the procedure and for at least 30 minutes.

CONCLUSION

The methodology described in this article allows monitoring of the dynamics of the BBB disruption process and characterization of its physiology in vivo, and represents a marked advantage over postmortem static studies.

Phase II clinical trial of Wilms tumor 1 peptide vaccination for patients with recurrent glioblastoma multiforme

OBJECT

The object of this study was to investigate the safety and clinical responses of immunotherapy targeting the WT1 (Wilms tumor 1) gene product in patients with recurrent glioblastoma multiforme (GBM).

METHODS

Twenty-one patients with WT1/HLA-A*2402-positive recurrent GBM were included in a Phase II clinical study of WT1 vaccine therapy. In all patients, the tumors were resistant to standard therapy. Patients received intra-dermal injections of an HLA-A*2402-restricted, modified 9-mer WT1 peptide every week for 12 weeks. Tumor size, which was obtained by measuring the contrast-enhanced area on magnetic resonance images, was determined every 4 weeks. The responses were analyzed according to Response Evaluation Criteria in Solid Tumors (RECIST) 12 weeks after the initial vaccination. Patients who achieved an effective response continued to be vaccinated until tumor progression occurred. Progression-free survival and overall survival after initial WT1 treatment were estimated.

RESULTS

The protocol was well tolerated; only local erythema occurred at the WT1 vaccine injection site. The clinical responses were as follows: partial response in 2 patients, stable disease in 10 patients, and progressive disease in 9 patients. No patient had a complete response. The overall response rate (cases with complete or partial response) was 9.5%, and the disease control rate (cases with complete or partial response as well as those in which disease was stable) was 57.1%. The median progression-free survival (PFS) period was 20.0 weeks, and the 6-month (26-week) PFS rate was 33.3%.

CONCLUSIONS

Although a small uncontrolled nonrandomized trial, this study showed that WT1 vaccine therapy for patients with WT1/HLA-A*2402-positive recurrent GBM was safe and produced a clinical response. Based on these results, further clinical studies of WT1 vaccine therapy in patients with malignant glioma are warranted.

Synthetic triterpenoids inhibit growth and induce apoptosis in human glioblastoma and neuroblastoma cells through inhibition of prosurvival Akt, NF-kappaB and Notch1 signaling

Glioblastomas are high-risk primary brain tumors that are generally unresponsive or only weakly responsive to the currently available antineoplastic agents. Thus novel therapeutic strategies and agents are urgently needed to treat these incurable cancers. Oleanolic acid and ursolic acid are naturally occurring triterpenoids that have been used in traditional Asian medicine as anti-inflammatory and anti-cancer agents. Recently, synthetic oleanolic acid triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) and its C-28 methyl ester (CDDO-Me) and C-28 imidazole (CDDO-Im) derivatives have been shown to exhibit potent antitumor activity against diverse types of tumor cell lines, including leukemia, multiple myeloma, osteosarcoma, breast, lung, and pancreatic cancer cell lines; however, the anticancer activity of these agents for brain tumors has not been reported. In the present study, we investigated the apoptosis-inducing activity of CDDOs in glioblastoma (U87MG, U251MG) and neuroblastoma (SK-N-MC) cell lines. Cell growth/viability (MTS) and cytotoxicity (LDH release) assays demonstrated that glioblastoma cell lines are least sensitive to CDDO, but are highly sensitive to CDDO-Me and CDDO-Im at concentrations of 2.5-10 muM. CDDO-Im and CDDO-Me were equipotenent in their growth inhibitory activity. The primary mode of tumor cell destruction was apoptosis as demonstrated by significant increase in the number of hypo-diploid (sub-G0) cells and annexin V-FITC binding. Induction of apoptosis was associated with the activation of procaspases-3, -8, and -9, mitochondrial depolarization and the release of cytochrome c from mitochondria. Furthermore, CDDO-Me inhibited the levels of anti-apoptotic and prosurvival p-Akt, NF-kappaB (p65) and Notch1 signaling molecules. These studies provide rationale for clinical evaluation of these novel agents for the management of lethal brain neoplasms.

Distinctive pattern of cannabinoid receptor type II (CB2) expression in adult and pediatric brain tumors

The efficacy of cannabinoids against high-grade glioma in animal models, mediated by two specific receptors, CB1 and CB2, raised promises for targeted treatment of the most frequent and malignant primary brain tumors. Unlike the abundantly expressed CB1, the CB2 receptor shows a restricted distribution in normal brain. Although brain tumors constitute the second most common malignancy in children and the prevalence of histological types of brain tumors vary significantly between the adult and pediatric populations, cannabinoid receptor expression in pediatric tumors remains unknown. In the present study, we compared the expression of the CB2 receptor in paraffin-embedded sections from primary brain tumors of adult and pediatric patients. Most glioblastomas expressed very high levels of CB2 receptors and the expression correlated with tumor grade. Interestingly, some benign pediatric astrocytic tumors, such as subependymal giant cell astrocytoma (SEGA), which may occasionally cause mortality owing to progressive growth, also displayed high CB2 immunoreactivity. The high levels of CB2 expression would predestine those tumors to be vulnerable to cannabinoid treatment. In contrast, all examined cases of embryonal tumors (medulloblastoma and S-PNET), the most frequently diagnosed malignant brain tumors in childhood, showed no or trace CB2 immunoreactivity. Our results suggest that the CB2 receptor expression depends primarily on the histopathological origin of the brain tumor cells and differentiation state, reflecting the tumor grade.

Acyl-based anandamide uptake inhibitors cause rapid toxicity to C6 glioma cells at pharmacologically relevant concentrations

Compounds blocking the uptake of the endogenous cannabinoid anandamide (AEA) have been used to explore the functions of the endogenous cannabinoid system in the CNS both in vivo and in vitro. In this study, the effects of four commonly used acyl-based uptake inhibitors [N-(4-hydroxyphenyl)arachidonylamide (AM404), N-(4-hydroxy-2-methylphenyl) arachidonoyl amide (VDM11), (5Z,8Z,11Z,14Z)-N-(3-furanylmethyl)-5,8,11,14-eicosatetraenamide (UCM707) and (9Z)-N-[1-((R)-4-hydroxybenzyl)-2-hydroxyethyl]-9-octadecen-amide (OMDM2)] and the related compound arvanil on C6 glioma cell viability were investigated. All five compounds reduced the ability of the cells to accumulate calcein, reduced the total nucleic acid content and increased the activity of lactate dehydrogenase recovered in the cell medium. AM404 (10 microm) and VDM11 (10 microm) acted rapidly, reducing cell viability after 3 h of exposure when cell densities of 5,000 per well were used. In contrast, UCM707 (30 microm), OMDM2 (10 microm) and the related compound arvanil (10 microm) produced a more slowly developing effect on cell viability, although robust effects were seen after 6-9 h of exposure. At higher cell densities, the toxicities of AM404 and UCM707 were reduced. Comparison of the compounds with arachidonic acid, arachidonic acid methyl ester, AEA, arachidonoyl glycine and oleic acid suggested that the toxicity of the arachidonoyl-based compounds was related primarily to the acyl side-chain rather than the head group. A variety of pre-treatments blocking possible metabolic pathways and receptor targets were tested, but the only consistent protective treatment against the effects of these compounds was the antioxidant N-acetyl-L-cysteine. It is concluded that AM404, VDM11, UCM707 and OMDM2 produce a rapid loss of C6 glioma cell viability over the same concentration range as is required for the inhibition of AEA uptake in vitro, albeit with a longer latency. Such effects should be kept in mind when acyl-derived compounds are used to probe the function of the endocannabinoid system in the CNS, particularly in chronic administration protocols.

Inhibitory effect of caffeic acid phenethyl ester on the growth of C6 glioma cells in vitro and in vivo

Caffeic acid phenethyl ester (CAPE), a component of honeybee propolis, has been reported to hold various biochemical responses. In the preliminary study, we found that CAPE inhibited the growth of C6 glioma cells in a dose dependent and time dependent manner as shown by the results of trypan blue dye exclusion assay and cell proliferation assay. In addition, the cell number percentage of the G0/G1 phase increased to 85% after the treatment with 50 microM of CAPE for 24h. After treatment with CAPE (50 microM) for 6h, it demonstrated that the protein level of hyperphosphorylated pRb decreased, and cyclin dependent kinase inhibitors p21, p27, and p16 were marked up-regulated. The association of CDK2 and cyclin E that affects the CDK2 activity decreased. When C6 cells were grown as xenografts in nude mice, treatment with CAPE (1-10mg/kg; ip) induced a significant dose dependent decrease in tumor growth by evaluating tumor volume and tumor weight. Histochemical and immunohistochemical analysis revealed that CAPE treatment significantly reduced the number of mitotic cells and proliferating cell nuclear antigen (PCNA)-positive cells in C6 glioma. These results suggest that CAPE presents an antitumor potential for glioma by inhibiting the growth of tumor cells.

Antiproliferative activities of iron and platinum conjugates of salicylaldehyde semi-/thiosemicarbazones against C6 glioma cells

The identification of novel therapeutic agents for the management of malignant gliomas represents an area of active research. Here, we show that among the iron and platinum complexes of 2-hydroxybenzaldehyde semi-/thiosemicarbazones the latter inhibits the growth of C6 glioma cells in vitro with an IC50 value of 45 microM. Structural characterization reveals iron complexes to be octahedral having intermediate S = 3/2 spin states while platinum complexes are found to be square planar moieties. Our findings suggest that the platinum compounds of 2-hydroxybenzaldehyde thiosemicarbazone are potential candidates for the treatment of malignant gliomas.

Cyclosporine a induces growth arrest or programmed cell death of human glioma cells

Human malignant gliomas are highly resistant to current therapeutic approaches. We previously demonstrated that cyclosporine A (CsA) induces an apoptotic cell death in rat C6 glioma cells. In the present study, we found the induction of growth arrest or cell death of human malignant glioma cells exposed to CsA. In studied glioma cells, an accumulation of p21Cip1/Waf1 protein, a cell cycle inhibitor, was observed following CsA treatment, even in the absence of functional p53 tumour suppressor. CsA induced a senescence-associated growth arrest, in U87-MG glioma cells with functional p53, while in U373 and T98G glioma cells with mutated p53, CsA treatment triggered cell death associated with alterations of cell morphology, cytoplasm vacuolation, and condensation of chromatin. In T98G cells this effect was completely abolished by simultaneous treatment with an inhibitor of protein synthesis, cycloheximide (CHX). Moreover, CsA-induced cell death was accompanied by activation of executory caspases followed by PARP cleavage. CsA treatment did not elevate fasL expression and had no effect on mitochondrial membrane potential. We conclude that CsA triggers either growth arrest or non-apoptotic, programmed cell death in human malignant glioma cells. Moreover, CsA employs mechanisms different to those in the action of radio- and chemotherapeutics, and operating even in cells resistant to conventional treatments. Thus, CsA or related drugs may be an effective novel strategy to treat drug-resistant gliomas or complement apoptosis-based therapies.

Toxicity, biodistribution, and convection-enhanced delivery of the boronated porphyrin BOPP in the 9L intracerebral rat glioma model

PURPOSE

To investigate the toxicity, biodistribution, and convection-enhanced delivery (CED) of a boronated porphyrin (BOPP) that was designed for boron neutron capture therapy and photodynamic therapy.

METHODS AND MATERIALS

For the toxicity study, Fischer 344 rats were injected with graded concentrations of BOPP (35-100 mg/kg) into the tail vein. For boron biodistribution studies, 9L tumor-bearing rats received BOPP either systematically (intravenously) or locally.

RESULTS

All rats that received 70 mg/kg BOPP and 70% of rats that received < or = 60 mg/kg BOPP i.v. either had to be euthanized or died within 4 days of injection. In the biodistribution study, boron levels were relatively high in liver, kidney, spleen, and adrenal gland tissue, and moderate levels were found in all other organs. The maximum tumor boron concentration was 21.4 mug/g at 48 h after i.v. injection; this concentration of boron in brain tumors is at the low end of the range considered optimal for therapy. In addition, the tumor/blood ratio (approximately 1.2) was not optimal. When BOPP was delivered directly into intracerebral 9L tumors with CED, we obtained tumor boron concentrations much greater than those obtained by i.v. injection. Convection-enhanced delivery of 1.5 mg BOPP produced an average tumor boron level of 519 mug/g and a tumor/blood ratio of approximately 1850:1.

CONCLUSIONS

Our study demonstrates that changing the method of BOPP delivery from i.v. to CED significantly enhances the boron concentration in tumors and produces very favorable tumor/brain and tumor/blood ratios.

Glioblastoma Patients Exhibit Circulating Tumor-Specific CD8+ T Cells

PURPOSE

There is growing interest in developing cellular immune therapies for glioblastoma multiforme, but little is known about tumor-specific T-cell responses. A glioblastoma multiforme-specific T-cell assay was developed using monocyte-derived dendritic cells to present tumor antigens from the established glioblastoma multiforme cell line U118.

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cells (PBMC) and tumor cells were obtained from nine patients with newly diagnosed brain tumors: five glioblastoma multiforme, two oligodendroglioma, one ependymoma, and one astrocytoma. PBMCs were incubated overnight with autologous tumor cells or autologous dendritic cells loaded with a U118 cell lysate, and responses were detected by IFN-gamma ELISPOT and cytokine flow cytometry assays.

RESULTS

PBMCs from all glioblastoma multiforme patients exhibited IFN-gamma responses to autologous tumor but not to HLA-mismatched U118 cells. Glioblastoma multiforme-specific IFN-gamma responses were primarily mediated by CD8+ T cells and represented approximately 2% of total CD8+ T cells. Additionally, all glioblastoma multiforme patients responded to autologous dendritic cells loaded with U118 lysate but not with low-grade astrocytoma cell lysates. PBMCs from four patients with other brain tumor types and one normal donor failed to respond to U118 lysate-loaded autologous dendritic cells. These data indicate that the IFN-gamma responses to U118 lysate-loaded autologous dendritic cells are glioblastoma multiforme specific. Moreover, PBMCs stimulated 1 to 2 weeks with U118 lysate-loaded dendritic cells exhibited MHC class I-restricted cytotoxicity against autologous tumor cells.

CONCLUSIONS

Glioblastoma multiforme patients exhibit circulating tumor-specific CD8+ T cells that recognize shared tumor antigens from the glioblastoma multiforme cell line U118. These data show that glioblastoma multiformes are immunogenic and support the development of immunotherapy trials.

MTH-68/H oncolytic viral treatment in human high-grade gliomas

Application of virus therapy to treat human neoplasms has over a three decade history. MTH-68/H, a live attenuated oncolytic viral strain of the Newcastle disease virus, is one of the viruses used in the treatment of different malignancies. Here we report on the administration of MTH-68/H to patients with glioblastoma multiforme, the most common and most aggressive neuroectodermal neoplasm with a poor prognosis, averaging six months to a year. Four cases of advanced high-grade glioma were treated with MTH-68/H after the conventional modalities of anti-neoplastic therapies had failed. This treatment resulted in survival rates of 5-9 years, with each patient still living today. Against all odds, each patient resumed a lifestyle that resembles their previous daily routines and enjoys a good quality of life, Each of these patients has regularly received MTH-68/H as their sole form of onco-therapy for a number of years now without interruption.

Temozolomide as first-line agent in treating high-grade gliomas: phase II study

Temozolomide a recent, oral, second generation alkylating agent is a chemotherapeutic with demonstrated efficacy for the treatment of high-grade gliomas; its efficacy has been demonstrated in both pre-clinical and phase I and II studies. The goal of this study is to determine the activity and safety of temozolomide in improving overall survival (OS), progression-free survival (PFS) and health-related quality of life (HQL) in patient with malignant gliomas. Forty-two patients with newly diagnosed glioblastoma, anaplastic astrocytoma and anaplastic oligodendroglioma were studied. The mean follow-up period was 12 months. The overall response rate (only responsive patient) for all histological groups was 40%, 10 patients (24%) showed a stabilization of disease. The median PFS and OS was respectively 8.35 and 14.1 months: time to progression was 34 week ranging from 21 to 47. In all patients, treatment with temozolomide was associated with improvement of performance status including the patient showing disease progression: Karnofski score improved in all patients by a minimum of 10, with a median of 20 at 6 months. No patient stopped the treatment due to side-effects, no major adverse events were recorded.

CONCLUSION

Temozolomide appears to be an ideal, first-line, single-agent, with a safe profile and demonstrated HQL benefits in patients with high-grade gliomas.

Inhibition of Akt kinase signalling and activation of Forkhead are indispensable for upregulation of FasL expression in apoptosis of glioma cells

Activation of Akt signalling pathway is frequently found in glioma cells and may contribute to their resistance to undergo apoptosis in response to conventional therapies. We found that cyclosporin A (CsA) induces apoptosis of C6 glioma cells, which is associated with transcriptional activation of fasL. In the present paper, we investigated an involvement of Akt signalling in the regulation of FasL expression in CsA-induced apoptosis. We demonstrated that the level of active Akt decreases significantly after CsA treatment, which results in the decrease of Forkhead phosphorylation and its translocation to the nucleus. It correlated with an increase of binding to the Forkhead-responsive element FHRE from the FasL promoter, as demonstrated by gel-shift assays. Although treatment with LY294002, a specific inhibitor of PI3 K, decreased the phosphorylation of Akt and increased Fkhr translocation to the nucleus, these events were not sufficient to induce FasL expression and apoptosis of C6 glioma cells. Interference with Akt/Forkhead signalling by membrane-targeted Akt or removal of the FKHR-binding sites from the FasL promoter significantly abolished its activation. These results indicate that downregulation of Akt signalling and activation of Forkhead is a prerequisite for the induction of FasL promoter. It may be clinically important for pharmacological intervention in gliomas.

Autologous adjuvant linked fibroblasts induce anti-glioma immunity: implications for development of a glioma vaccine

OBJECTIVES

Adjuvant-linked vaccines have been shown to induce anti-tumor immunity in patients with a variety of solid tumors. In this study we describe an in vitro model of active immunotherapy using autologous fibroblasts as immunogen. Correlative results from glioma patients immunized with autologous fibroblasts are also described.

METHODS

Peripheral blood lymphocytes (PBLs) from normal subjects were immunized in vitro against autologous skin fibroblasts coupled to the adjuvant muramyl dipeptide. The lymphocytes developed cell-mediated cytotoxicity that was measured with a short-term chromium release assay. Results of in vitro experiments were compared to data derived from glioma patients immunized with subcutaneous injection of an autologous adjuvant-linked fibroblast vaccine. Glioma target cells and fibroblast immunogens were derived from early passage primary tissue culture.

RESULTS

A comparison of autologous vs. homologous immunogen indicated that major histocompatibility complex matching was required at the sensitization stage of immunity (17.2 +/- 3.4% specific lysis vs. 0.4 +/- 3.1%, P < 0.01). Pre-treatment of fibroblast immunogen cells with interferon gamma (IFN-gamma) was found to significantly increase immunity (42.2 +/- 10.0%, P < 0.01), as did IFN-gamma pre-treatment of tumor target cells (35.8 +/- 9.0%, P < 0.01). The positive effect of IFN-gamma was diminished by treatment of cells with IFN-alpha. These in vitro results correlated well with in vivo data derived from glioma patients immunized with an autologous adjuvant-linked fibroblast vaccine. PBLs from patients developed direct cell-mediated cytotoxicity against autologous tumor cells. Lysis of tumor targets after in vivo immunization increased over a three-week interval (from 1.2 +/- 3.0% to 21.0 +/- 3.4%, P < 0.01) while lysis of a non-MHC matched control cell line remained essentially unchanged.

CONCLUSIONS

Specific lysis of glioma targets in vitro was achieved after in vivo sensitization with autologous adjuvant-linked fibroblasts. Collectively, the data indicate that biochemically modified autologous cells can stimulate anti-glioma immunity in humans. The degree of specific immunity seen in our patients compares favorably with other published series using glioma cells as an antigenic source. Accordingly, fibroblasts may represent a practical alternative to glioma cells for vaccine construction.

Survivin in brain tumors: an attractive target for immunotherapy

Survivin, a member of the inhibitor of apoptosis proteins gene family, was recently shown to be expressed by tumors originating from different cell lineages. There are also cumulative evidences that spontaneous immune response against survivin derived epitopes may occur. Here, using RT-PCR, Western-blot analysis and immunohistochemistry, we show that survivin is widely expressed by gliomas, meningiomas and schwannomas, both in vitro and in vivo. These data indicate that survivin may serve as an attractive target for immunotherapies designed for brain tumors.

Survival improvement in patients with glioblastoma multiforme during the last 20 years in a single tertiary-care center

METHODOLOGY

The survival of 357 consecutive patients with newly diagnosed glioblastoma multiforme (GBM) in three treatment groups reflecting different time-periods of diagnosis (A: 1982-1984; B: 1994/1995; C: 1996-1998) was analysed to assess the impact and the potential improvement of changing treatment strategies in our tertiary-care center.

PATIENTS AND METHODS

Group A (n = 100) included all consecutive patients diagnosed from 1982 to 1984 and served as the historical control. Group B (n = 93) included all consecutive patients diagnosed in 1994/1995 and group C (n = 164) those diagnosed from 1996 to 1998. Survival in the three treatment groups (A vs. B vs. C) was analysed according to treatment given after neurosurgical intervention (i.e. no specific therapy versus radiotherapy versus combined radio-/chemotherapy), and according to first-line chemotherapy, age (< 40, 40-60, > 60), sex, and tumor location (hemispheric versus bilateral or multifocal tumors, and tumors involving eloquent brain areas). Survival was analysed using Kaplan-Meier's non-parametric method. A p-value < 0.05 was considered statistically significant.

RESULTS

Patients in groups A and B received radio- and/or chemotherapy to a varying extent (radiotherapy: group A: 22%, group B: 62%; chemotherapy: group A: 6%, group B: 33%). Chemotherapy was administered after termination of radiotherapy in both groups. In group C, 96% of patients received combined radio-/chemotherapy which was administered concomitantly and started within three weeks after surgery. Median survival was 5.2 months in group A, 5.1 months in group B and 14.5 months in C (p < 0.0001). Nine patients in group A (9%), 9 in group B (10%) and 40 in group C (25%) survived more than 18 months (p < 0.05).

CONCLUSIONS

Survival improvement in group C might be attributable to the early start of combined radio-/chemotherapy. Therapy was administered on a complete outpatient basis, enabled by a dedicated interdisciplinary neuro-oncologic team caring for group C. Toxicity was mild and patients' acceptance excellent.

Apoptotic DNA endonuclease (DNase-gamma) gene transfer induces cell death accompanying DNA fragmentation in human glioma cells

AIMS

Both the genetic restoration of the apoptotic pathway and the introduction of proapoptotic molecules are now drawing attention. Concerning apoptosis of human glioma cells induced by human interferon-beta protein, we found that DNA endonuclease (DNase-gamma) acts as an executive molecule. The authors investigated whether gene transfer of this DNase-gamma exerts some therapeutic effects on human glioma cells.

METHODS

We transduced U251SP, U251MG, and T98G human glioma cells with DNase-gamma gene via multilamellar cationic liposomes, monitored the growth of those cells, and carefully observed the cell-death pattern.

RESULTS

DNase-gamma gene transfer resulted in an overexpression of DNase-gamma protein and induced DNA fragmentation in gene-transferred cells. The cytotoxic effect rose with multiple inoculations of the liposome, suggesting a relationship between its expression and the therapeutic effect.

CONCLUSIONS

These results demonstrate that DNase-gamma gene transfer can induce apoptosis in human glioma cells, indicating its potential to become a future gene therapy strategy.

The surgical bed after BCNU polymer wafer placement for recurrent glioma: serial assessment on CT and MR imaging

OBJECTIVE

The objective of our study was to describe the CT and MR imaging appearances of the surgical bed in the brains of patients receiving biodegradable polymers impregnated with N, N'1, 3-Bis-(2-chloroethyl)-N-nitrosourea (BCNU) for recurrent glioma and to determine whether patients receiving placebos could be differentiated from those receiving BCNU based on the pattern and growth kinetics of tumor recurrence.

MATERIALS AND METHODS

The CT and MR images of 20 patients who underwent surgery for resection of recurrent high-grade gliomas and placement of intratumoral wafers (11 received BCNU polymer wafers, nine received control wafers) were analyzed for wafer appearance, volume of gas in the tumor bed, and volume of enhancement on serial scans.

RESULTS

Wafers appeared as linear hyperdense structures on CT and as linear low-signal-intensity structures on MR imaging and caused no significant enhancement. In the BCNU polymer group, gas volume was 4.0 +/- 3.4 cm(3) (mean +/- SD), whereas gas volume was 1.6 +/- 3.0 cm(3) for the placebo group (Mann-Whitney test, p = 0.03). A trend toward linear rather than exponential recurrent tumor growth was identified for the BCNU polymer group but not for the placebo group.

CONCLUSION

BCNU polymer wafers have a specific appearance on CT and MR imaging with which radiologists should be familiar: gas in the surgical bed is an expected transient finding, and tumor regrowth in patients receiving BCNU polymer wafers appeared to occur at a slower rate than in those receiving the placebo.

T-cell immune responses in the brain and their relevance for cerebral malignancies

In order that cellular immune responses afford protection without risk to sensitive normal tissue, they must be adapted to individual tissues of the body. Nowhere is this more critical than for the brain, where various passive and active mechanisms maintain a state of immune privilege that can limit high magnitude immune responses. Nevertheless, it is now clear that immune responses are induced to antigens in the brain, including those expressed by cerebral malignancies. We discuss hypotheses of how this can occur, although details such as which antigen presenting cells are involved remain to be clarified. Antitumor responses induced spontaneously are insufficient to eradicate malignant astrocytomas; many studies suggest that this can be explained by a combination of low level immune response induction and tumor mediated immunosuppression. A clinical objective currently pursued is to use immunotherapy to ameliorate antitumour immunity. This will necessitate a high level immune response to ensure sufficient effector cells reach the tumor bed, focused cytotoxicity to eradicate malignant cells with little collateral damage to critical normal cells, and minimal inflammation. To achieve these aims, priority should be given to identifying more target antigens in astrocytoma and defining those cells present in the brain parenchyma that are essential to maintain antitumour effector function without exacerbating inflammation. If we are armed with better understanding of immune interactions with brain tumor cells, we can realistically envisage that immunotherapy will one day offer hope to patients with currently untreatable neoplastic diseases of the CNS.

Study of in vitro and in vivo effects of the piperidine nitroxide Tempol--a potential new therapeutic agent for gliomas

The identification of novel therapeutic agents for the management of malignant gliomas represents an area of active research. Here, we show that Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl; TPL), a stable nitroxide free radical, inhibits the growth of C6 glioma cells both in vitro and in vivo. Morphological features of apoptosis were apparent in C6 cells following in vitro treatment with TPL. Cell death was preceded by dose-dependent increase in p21(WAF1/CIP1) expression, without apparent stabilisation of the TP53 gene product. When C6 cells were grown as xenografts in nude mice, treatment with TPL induced a significant dose-dependent decrease in tumour growth, without signs of general or organ toxicity. Tumours from treated mice showed an increase in the number of apoptotic cells and a decrease in the rate of neo-vascularisation compared with tumours from control mice. Our findings suggest a potential use for TPL as a novel antiproliferative agent for the treatment of malignant gliomas.

Feasibility and toxicity of CCNU therapy in elderly patients with glioblastoma multiforme

In our institution, 103 glioblastoma multiforme (GBM) patients aged from 55 to 83 years were treated since November 1994 as follows. All patients underwent surgical intervention (gross total resection, n = 35; subtotal resection, n = 38; stereotactic biopsy, n = 30). Subsequently all patients were offered radiotherapy and chemotherapy with CCNU. Results were as follows: 101 patients started radiotherapy, 93 patients completed it (96% of the patients aged < 65 years and 85% of the patients > or =65 years). All patients received at least 1 cycle of chemotherapy (median 3 cycles). Chemotherapy-associated toxicity was generally mild, more pronounced in females and did not increase with age. Median time to progression was 10.5+/-3.2 months for the patients < 65 years and 5.1+/-1 months for patients > or =65 years. median overall survival was 17.5+/-3.8 months in patients < 65 years and 8.6+/-1 months in patients > or =65 years (p < 0.0001). In multivariate analysis, age and female sex remained independent prognostic factors. Our data indicate that a treatment concept including concomitant radio- and chemotherapy is feasible even in elderly patients with GBM.

Clinical immunotherapy for brain tumors

As an immunization platform for brain tumors, dendritic cells supply an impressive host of advantages. On the simplest level, they provide the safety and tumor-specificity so wanted by current therapeutic options. Yet, in addition, as the fundamental antigen-presenting cell, they circumvent many of the immunologic challenges that gliomas and the CNS proffer and that other immunotherapeutic modes fail to overcome. Directions to take now include the identification of new tumor-specific and tumor-associated antigens; the determination of the optimal dendritic cell subtype, generation, loading method, maturation state, dose, and route of delivery for immunizations; the further characterization of dendritic cells and their activities; and, potentially, the discovery of ways to pulse dendritic cells efficiently in vivo. Preclinical studies continue to play an important role in refining this form of active immunotherapy.

The molecular genetics of therapeutic resistance in malignant astrocytomas

The adverse prognosis associated with malignant astrocytomas (MA) is due in part to the development of resistance by the tumor to chemo- and radiotherapy-induced cytotoxic damage. The mechanisms of resistance are poorly understood but function at the level of the endothelial cell, the blood-brain barrier and the neoplastic cell itself. The classic examples of drug resistance proteins, such as the p-glycoprotein/multidrug resistance protein 1, have been identified within MA biopsy specimens. However, it is questionable to what degree, if at all, these proteins contribute directly to the evolution and prognosis of the MA. Surprisingly, there are specific genes, not traditionally associated with resistance, which appear increasingly relevant to both tumor progression and insensitivity to cytotoxic damage. These genes are involved in cell cycle regulation, and include the retinoblastoma susceptibility gene (Rb), the tumor suppressor gene p53, as well as those encoding the cyclins, their kinases and inhibitors. The interaction between the products of these genes and intratumoral environmental factors appears to involve a dynamic and prognostically adverse selection process. It is from this perspective that the mechanism(s) of hypoxic-ischaemic selection for resistance and its therapeutic repercussions will be analyzed.

Erucylphosphocholine-induced apoptosis in glioma cells: involvement of death receptor signalling and caspase activation

Erucylphosphocholine (ErPC) is a promising anti-neoplastic drug for the treatment of malignant brain tumours. It exerts strong anti-cancer activity in vivo and in vitro and induces apoptosis even in chemoresistant glioma cell lines. The purpose of this study was to expand on our previous observations on the potential mechanisms of ErPC-mediated apoptosis with a focus on death receptor activation and the caspase network. A172 and T98G glioma cells were treated with ErPC for up to 48 h. ErPC effects on the expression of the tumour necrosis factor (TNF) and TNF-related apoptosis-inducing ligand (TRAIL) receptor system, and on caspase activation were determined. ErPC had no effect on the expression of TNFalpha or TRAIL. Inhibition of the TNF or TRAIL signalling pathway with antagonistic antibodies or fusion proteins did not affect apoptosis induced by ErPC, and a dominant-negative FADD construct did not abolish ErPC-induced effects. Western blot analysis indicated that ErPC-triggered apoptosis resulted in a time-dependent processing of caspases-3, -7, -8 and -9 into their respective active subunits. Co-treatment of A172 cells with different caspase inhibitors prevented apoptosis but did not abrogate cell death. These data suggest that A172 cells might have an additional caspase-independent pathway that insures cell death and guarantees killing of those tumour cells whose caspase pathway is incomplete.

Intratumoral doxorubicin in patients with malignant brain gliomas

The objective of the study was to evaluate the safety and therapeutic efficacy of intralesional administration of doxorubicin in brain gliomas. Ten patients with recurrent grade III or IV glioma were enrolled in the study, after the second operation. All patients had not responded to radiation therapy. Chemotherapy was administered directly in the tumor through an Ommaya pump placed in the site of disease at the time of craniotomy. Doxorubicin 0.5 mg was administered in the Ommaya reservoir every 24 hours on days 1 to 10. Patients were evaluated at 6- to 8-week intervals until tumor progression and death. All patients were evaluated for response. Six of 10 patients had clinical improvement lasting from 12 to 73 weeks. Objective radiologic response was observed in 5 of 10 (50%) patients. One patient achieved complete response with time to disease progression of 119 weeks, and 4 patients had a partial response (duration 14-39 weeks) with 25% or more reduction of tumor volume on computed tomography scan compared with pretreatment measurements. Time to disease progression in patients who responded after the intratumoral chemotherapy was 39.83 +/- 40.5 weeks. One additional patient had stable disease for a duration of 12 weeks. The median survival of the patients with response was 55.17 +/- 54.22 weeks (range: 21-164 weeks), whereas survival of those who did not respond was 17.0 +/- 12.36 weeks (range: 8-35) (Mann Whitney U test: z = -2.13, p = 0.033). The median survival of all 10 patients was 39.9 +/- 45.52 weeks (range: 8-73 weeks). Bifrontal headache was reported in 4 of 10 patients immediately after the administration of doxorubicin. There were no other clinically significant adverse reactions either in the brain or systematically. Intralesional administration of doxorubicin appears to be a safe and effective treatment and should be further explored in the management of brain gliomas resistant to conventional forms of treatment.

Pharmacotherapy of malignant astrocytomas of children and adults: current strategies and future trends

This article reviews the conceptual progression in the pharmacological therapy of malignant astrocytoma (MA) over the past decade, and its future trends. It is a selective rather than an exhaustive inventory of literature citations. The experience of the Brain Tumour Cooperative Group (BTCG) and earlier phase III trials are summarised to place subsequent phase II and I studies of single and combination agent chemotherapy in perspective. The BTCG experience of the 1970s to 1980s may be summarised to indicate that external beam radiotherapy (EBRT) is therapeutic, although not curative, and not further improved upon by altering fractionation schedules, or the addition of radioenhancers. Whole brain and reduced whole brain EBRT with focal boost were comparable regimens. Nitrosourea-based, adjuvant chemotherapy provided a modest improvement in survival among adult patients, which was comparable with that of other single drugs or multidrug regimes. The multiagent schedules, however, had a correspondingly higher toxicity rate. Intra-arterial administration was associated with significant risk, which conferred no therapeutic advantage. The trend of the past decade has been towards multiagent chemotherapy although its benefit cannot be predicted from the classic prognostic factors. Published experience with investigational trials utilising myeloablative chemotherapy with autologous bone marrow or peripheral blood stem cell haemopoietic support, drug delivery enhancement methods and radiosensitisers is critically reviewed. None of these approaches have achieved wide-spread acceptance in the treatment of adult patients with MA. Greater attention is placed on recent 'chemoradiotherapy' trials, which attempt to integrate and maximise the cytoreductive potential of both modalities. This approach holds promise as an effective means to delay or overcome the evolution of tumour resistance, which is probably one of the dominant determinants of prognosis. However, the efficacy of this approach remains unproven. New chemotherapeutic agents as well as biological response modifiers, protein kinase inhibitors, angiogenesis inhibitors and gene therapy are also discussed; their role in the therapeutic armamentarium has not been defined.

Analysis of FasL and TRAIL induced apoptosis pathways in glioma cells

FasL and TNF-related apoptosis-inducing ligand (TRAIL) belong to a subgroup of the TNF superfamily which induce apoptosis by binding to their death domain containing receptors. In the present study we have utilized a panel of seven cell lines derived from human malignant gliomas to characterize molecular pathways through which FasL and TRAIL induce apoptosis in sensitive glioma cells and the mechanisms of resistance in cell lines which survive the death stimuli. Our findings indicate that FADD and Caspase-8 are essential for FasL and TRAIL mediated apoptosis in glioma cells. One sensitive cell line (D270) can be protected from FasL and TRAIL induced death by anti-apoptotic Bcl-2 family members while another (D645) cannot, implying that these lines may represent glioma examples of type II and type I cells respectively. For the first time we demonstrate resistance to FasL but not to TRAIL within the one glioma cell line. Furthermore, we report distinct mechanisms of resistance within different glioma lines, including downregulation of Caspase-8 in U373MG. Cycloheximide sensitized four of the resistant cell lines suggesting the presence of labile inhibitors. None of the known apoptosis inhibitors examined accounted for the observed resistance, suggesting novel inhibitors may exist in glioma cells.

Brain glioma and human leukocyte antigens (HLA)--is there an association

Expression of human leukocyte antigens (HLA) is important for the immune response against infectious agents and malignant cells. Association of single HLA antigens or HLA haplotypes with disease has been investigated previously, and positive correlations between HLA and some cancers, such as cervical or nasopharyngeal carcinomas have been reported. In the present study, HLA antigen frequencies of 65 adult Caucasian patients with low-grade, anaplastic, or malignant astrocytic glioma (WHO grades II-IV) were compared with 157 racially similar, asymptomatic control individuals. Both standard serologic and PCR techniques for HLA typing were employed for all patients and controls. Our results suggest a positive association between single HLA antigens and presence of symptomatic cerebral glioma. Compared with the control population, patients positive for HLA-A*25 had a 3.0-fold increased risk of glioma (p = 0.04), patients positive for HLA-B*27, a 2.7-fold risk (p = 0.03), and patients positive for HLA-DRB1*15, a 2.2-fold risk (p = 0.03), whereas HLA-DRB1*07 was associated with a 0.4-fold decreased risk of glioma (p = 0.02). Occurrence rate of some HLA antigen combinations and estimated haplotypes was also different in glioma patients. Thus, HLA-DRB1*15:DRB5*(51) occurrence in combination with HLA-DRB1*11 was associated with a 13.4-fold increased risk of glioma (p = 0.001), and the incidence of HLA-Cw*6:DRB1*07 with a 0.2-fold decreased risk of glioma (p = 0.03). In conclusion, single HLA antigens and their combinations and estimated haplotypes are possibly significantly more or less frequent in persons developing symptomatic cerebral glioma during their adult life, compared with asymptomatic individuals.

Multicenter phase II trial of temozolomide in patients with glioblastoma multiforme at first relapse

BACKGROUND

Recurrent glioblastoma multiforme (GBM) is resistant to most therapeutic endeavors, with low response rates and survival rarely exceeding six months. There are no clearly established chemotherapeutic regimens and the aim of treatment is palliation with improvement in the quality of life.

PATIENTS AND METHODS

We report an open-label, uncontrolled, multicenter phase II trial of temozolomide in 138 patients (intent-to-treat [ITT] population) with glioblastoma multiforme at first relapse and a Karnofsky performance status (KPS) > or = 70. One hundred twenty-eight patients were histologically confirmed with GBM or gliosarcoma (GS) by independent central review. Chemotherapy-naïve patients were treated with temozolomide 200 mg/m2/day orally for the first five days of a 28-day cycle. Patients previously treated with nitrosourea-containing adjuvant chemotherapy received 150 mg/m2/day for the first five days of a 28-day cycle. In the absence of grade 3 or 4 toxicity, patients on the 150 mg/m2 dose schedule were eligible for a 200 mg/m2 dose on the next cycle.

RESULTS

The primary endpoint was six-month progression-free survival assessed with strict radiological and clinical criteria. Secondary endpoints included radiological response and Health-related Quality of Life (HQL). Progression-free survival at six months was 18% (95% confidence interval (CI): 11%-26%) for the eligible-histology population. Median progression-free survival and median overall survival were 2.1 months and 5.4 months, respectively. The six-month survival rate was 46%. The objective response rate (complete response and partial response) determined by independent central review of gadolinium-enhanced magnetic resonance imaging (MRI) scans was 8% for both the ITT and eligible-histology populations, with an additional 43% and 45% of patients, respectively, having stable disease (SD). Objectively assessed response and maintenance of a progression-free status were both associated with HQL benefits (characterized by improvements over baseline in HQL domains). Temozolomide had an acceptable safety profile, with only 9% of therapy cycles requiring a dose reduction due to thrombocytopenia. There was no evidence of cumulative hematologic toxicity.

CONCLUSIONS

Temozolomide demonstrated modest clinical efficacy, with an acceptable safety profile and measurable improvement in quality of life in patients with recurrent GBM. The use of this drug should be explored further in an adjuvant setting and in combination with other agents.

Serum-dependent effects of tamoxifen and cannabinoids upon C6 glioma cell viability

In the present study, the effects of the combination of tamoxifen ((Z)-2[p-(1,2-diphenyl-1-butenyl)phenoxy]-N,N-dimethylamine citrate) and three cannabinoids (Delta(9)-tetrahydrocannabinol [Delta(9)-THC], cannabidiol, and anandamide [AEA]) upon the viability of C6 rat glioma cells was assessed at different incubation times and using different culturing concentrations of foetal bovine serum (FBS). Consistent with previous data for human glioblastoma cells, the tamoxifen sensitivity of the cells was increased as the FBS content of the culture medium was reduced from 10 to 0.4 and 0%. The cells expressed protein kinase C alpha and calmodulin (the concentration of which did not change significantly as the FBS concentration was reduced), but did not express estrogen receptors. Delta(9)-THC and cannabidiol, but not AEA, produced a modest reduction in cell viability after 6 days of incubation in serum-free medium, whereas no effects were seen in 10% FBS-containing medium. There was no observed synergy between the effects of tamoxifen and the cannabinoids upon cell viability.

Anti-VEGF antibody treatment of glioblastoma prolongs survival but results in increased vascular cooption

Vascular endothelial growth factor (VEGF) is an important mediator of the intense angiogenesis which is characteristic of glioblastoma. While genetic manipulation of VEGF/VEGF receptor expression has previously been shown to inhibit glioblastoma growth, to date, no study has examined the efficacy of pharmacologic blockade of VEGF activity as a means to inhibit intracranial growth of human glioblastoma. Using intraperitoneal administration of a neutralizing anti-VEGF antibody, we demonstrate that inhibition of VEGF significantly prolongs survival in athymic rats inoculated in the basal ganglia with G55 human glioblastoma cells. Systemic anti-VEGF inhibition causes decreased tumor vascularity as well as a marked increase in tumor cell apoptosis in intracranial tumors. Although intracranial glioblastoma tumors grow more slowly as a consequence of anti-VEGF treatment, the histologic pattern of growth suggests that these tumors adapt to inhibition of angiogenesis by increased infiltration and cooption of the host vasculature.

Involvement of the glutathione S-conjugate compounds and the MRP protein in Tc-99m-tetrofosmin and Tc-99m-sestamibi uptake in glioma cell lines

The objective of this study was to compare the accumulation of Tc-99m-tetrofosmin and Tc-99m-sestamibi in four grade IV glioma cell lines and to correlate their accumulation with the multidrug resistance of the cells. Tc-99m-tetrofosmin in all glioma cell lines showed slightly higher uptake and more efficient release beyond 150 min than Tc-99m-sestamibi and the retention of both tracers in the cells was to a certain extend inversely proportional to their degree of multidrug resistance. The results obtained showed that the efflux of both tracers was carried out only in part through the MRP/GS-X pump system. Tc-99m-tetrofosmin showed good potential as a marker of recurrent malignant glioma and in vivo studies are currently underway to confirm these observations.

Molecular mechanisms of resistance to taxanes and therapeutic implications

The mechanism of resistance to taxanes has not been fully elucidated. Since Taxol is a substrate for P-glycoprotein, overexpression of this transport system is recognized as a relevant mechanism of resistance. Additional mechanisms include changes of microtubule structure and/or composition resulting in reduced drug binding to the target. Current efforts are directed at clarifying the role of cellular response to drug-induced damage to cytoskeleton and mitotic spindle. Downstream events, such as control of cell cycle progression and regulation of cell death pathways, are likely to play a relevant role in cellular sensitivity to antimicrotubule agents. The identification of resistance factors and critical determinants of antitumor efficacy of microtubule-stabilizing agents is essential to (i) improve their therapeutic efficacy; and (ii) to design non-cross-resistant compounds. The present review discusses the possible therapeutic implications of the recent progress in the field of resistance to taxanes. Copyright 1999 Harcourt Publishers Ltd.