Showing papers in "Neuro-oncology in 2005"
TL;DR: This review article describes the current knowledge about the nature of pericytes and their functions during vessel growth, vessel maintenance, and pathological angiogenesis.
Abstract: Blood vessels are composed of two interacting cell types. Endothelial cells form the inner lining of the vessel wall, and perivascular cells—referred to as pericytes, vascular smooth muscle cells or mural cells—envelop the surface of the vascular tube. Over the last decades, studies of blood vessels have concentrated mainly on the endothelial cell component, especially when the first angiogenic factors were discovered, while the interest in pericytes has lagged behind. Pericytes are, however, functionally significant; when vessels lose pericytes, they become hemorrhagic and hyperdilated, which leads to conditions such as edema, diabetic retinopathy, and even embryonic lethality. Recently, pericytes have gained new attention as functional and critical contributors to tumor angiogenesis and therefore as potential new targets for antiangiogenic therapies. Pericytes are complex. Their ontogeny is not completely understood, and they perform various functions throughout the body. This review article describes the current knowledge about the nature of pericytes and their functions during vessel growth, vessel maintenance, and pathological angiogenesis.
1,389 citations
TL;DR: A precise definition of the mechanisms by which IL-8 exerts its proangiogenic functions requires further study for the development of effectiveIL-8-targeted therapies.
Abstract: Interleukin-8 (IL-8, or CXCL8), which is a chemokine with a defining CXC amino acid motif that was initially characterized for its leukocyte chemotactic activity, is now known to possess tumorigenic and proangiogenic properties as well. In human gliomas, IL-8 is expressed and secreted at high levels both in vitro and in vivo, and recent experiments suggest it is critical to glial tumor neovascularity and progression. Levels of IL-8 correlate with histologic grade in glial neoplasms, and the most malignant form, glioblastoma, shows the highest expression in pseudopalisading cells around necrosis, suggesting that hypoxia/anoxia may stimulate expression. In addition to hypoxia/anoxia stimulation, increased IL-8 in gliomas occurs in response to Fas ligation, death receptor activation, cytosolic Ca2+, TNF-α, IL-1, and other cytokines and various cellular stresses. The IL-8 promoter contains binding sites for the transcription factors NF-κB, AP-1, and C-EBP/NF-IL-6, among others. AP-1 has been shown to mediate IL-8 upregulation by anoxia in gliomas. The potential tumor suppressor ING4 was recently shown to be a critical regulator of NF-κB-mediated IL-8 transcription and subsequent angiogenesis in gliomas. The IL-8 receptors that could contribute to IL-8-mediated tumorigenic and angiogenic responses include CXCR1 and CXCR2, both of which are G-protein coupled, and the Duffy antigen receptor for cytokines, which has no defined intracellular signaling capabilities. The proangiogenic activity of IL-8 occurs predominantly following binding to CXCR2, but CXCR1 appears to contribute as well through independent, small-GTPase activity. A precise definition of the mechanisms by which IL-8 exerts its proangiogenic functions requires further study for the development of effective IL-8-targeted therapies.
665 citations
TL;DR: Hypoxia-inducible factor 1 (HIF-1) is a critical regulatory factor in the tumor microenvironment because of its central role in promoting proangiogenic and invasive properties.
Abstract: Glioblastomas, like other solid tumors, have extensive areas of hypoxia and necrosis. The importance of hypoxia in driving tumor growth is receiving increased attention. Hypoxia-inducible factor 1 (HIF-1) is one of the master regulators that orchestrate the cellular responses to hypoxia. It is a heterodimeric transcription factor composed of alpha and beta subunits. The alpha subunit is stable in hypoxic conditions but is rapidly degraded in normoxia. The function of HIF-1 is also modulated by several molecular mechanisms that regulate its synthesis, degradation, and transcriptional activity. Upon stabilization or activation, HIF-1 translocates to the nucleus and induces transcription of its downstream target genes. Most important to gliomagenesis, HIF-1 is a potent activator of angiogenesis and invasion through its upregulation of target genes critical for these functions. Activation of the HIF-1 pathway is a common feature of gliomas and may explain the intense vascular hyperplasia often seen in glioblastoma multiforme. Activation of HIF results in the activation of vascular endothelial growth factors, vascular endothelial growth factor receptors, matrix metalloproteinases, plasminogen activator inhibitor, transforming growth factors alpha and beta, angiopoietin and Tie receptors, endothelin-1, inducible nitric oxide synthase, adrenomedullin, and erythropoietin, which all affect glioma angiogenesis. In conclusion, HIF is a critical regulatory factor in the tumor microenvironment because of its central role in promoting proangiogenic and invasive properties. While HIF activation strongly promotes angiogenesis, the emerging vasculature is often abnormal, leading to a vicious cycle that causes further hypoxia and HIF upregulation.
588 citations
TL;DR: Because the heterotopic-to-orthotopic transfer and propagation of glioblastoma multiforme preserves the receptor tyrosine kinase (RTK) gene amplification of patient tumors, this approach should facilitate investigations for determining the extent to which RTK amplification status influences tumor response to RTK-directed therapies.
Abstract: We have previously described a panel of serially transplantable glioblastoma multiforme xenograft lines established by direct subcutaneous injection of patient tumor tissue in the flanks of nude mice. Here we report the characterization of four of these lines with respect to their histopathologic, genetic, and growth properties following heterotopic-to-orthotopic (flank-to-intracranial) transfer. Cells from short-term cultures, established from excised flank xenografts, were harvested and injected into the brains of nude mice (106 cells per injection). The intracranial tumors generated from these injections were all highly mitotic as well as highly invasive, but they lacked necrotic features in most instances and failed to show endothelial cell proliferation in all instances. For mice receiving injections from a common explant culture, tumor intracranial growth rate was consistent, as indicated by relatively narrow ranges in survival time. In contrast to the loss of epidermal growth factor receptor gene (EGFR) amplification in cell culture, high-level amplification and overexpression of EGFR were retained in intracranial tumors established from two EGFR-amplified flank tumors. A third intracranial tumor retained patient tumor amplification and high-level expression of platelet-derived growth factor receptor alpha gene. Because the heterotopic-to-orthotopic transfer and propagation of glioblastoma multiforme preserves the receptor tyrosine kinase (RTK) gene amplification of patient tumors, this approach should facilitate investigations for determining the extent to which RTK amplification status influences tumor response to RTK-directed therapies. The fact that such studies were carried out by using an invasive tumor model in an anatomically appropriate context should ensure a rigorous preclinical assessment of agent efficacy.
319 citations
TL;DR: Current knowledge of how the SF/HGF:c-Met pathway contributes to brain tumor malignancy with a focus on glioma angiogenesis is summarized.
Abstract: The multifunctional growth factor scatter factor/hepatocyte growth factor (SF/HGF) and its receptor tyrosine kinase c-Met have emerged as key determinants of brain tumor growth and angiogenesis. SF/HGF and c-Met are expressed in brain tumors, the expression levels frequently correlating with tumor grade, tumor blood vessel density, and poor prognosis. Overexpression of SF/HGF and/or c-Met in brain tumor cells enhances their tumorigenicity, tumor growth, and tumor-associated angiogenesis. Conversely, inhibition of SF/HGF and c-Met in experimental tumor xenografts leads to inhibition of tumor growth and tumor angiogenesis. SF/HGF is expressed and secreted mainly by tumor cells and acts on c-Met receptors that are expressed in tumor cells and vascular endothelial cells. Activation of c-Met leads to induction of proliferation, migration, and invasion and to inhibition of apoptosis in tumor cells as well as in tumor vascular endothelial cells. Activation of tumor endothelial c-Met also induces extracellular matrix degradation, tubule formation, and angiogenesis in vivo. SF/HGF induces brain tumor angiogenesis directly through only partly known mechanisms and indirectly by regulating other angiogenic pathways such as VEGF. Different approaches to inhibiting SF/HGF and c-Met have been recently developed. These include receptor antagonism with SF/HGF fragments such as NK4, SF/HGF, and c-Met expression inhibition with U1snRNA/ribozymes; competitive ligand binding with soluble Met receptors; neutralizing antibodies to SF/HGF; and small molecular tyrosine kinase inhibitors. Use of these inhibitors in experimental tumor models leads to inhibition of tumor growth and angiogenesis. In this review, we summarize current knowledge of how the SF/HGF:c-Met pathway contributes to brain tumor malignancy with a focus on glioma angiogenesis.
299 citations
TL;DR: It is concluded that surgery should usually be the primary treatment with radiation given as adjuvant therapy with major differences in the outcomes indicate a true difference resulting from treatment.
Abstract: Radiotherapy has been the primary therapy for managing metastatic spinal disease; however, surgery that decompresses the spinal cord circumferentially, followed by reconstruction and immediate stabilization, has also proven effective. We provide a quantitative comparison between the “new” surgery and radiotherapy, based on articles that report on ambulatory status before and after treatment, age, sex, primary neoplasm pathology, and spinal disease distribution. Ambulation was categorized as “success” or “rescue” (proportion of patients ambulatory after treatment and proportion regaining ambulatory function, respectively). Secondary outcomes were also analyzed. We calculated cumulative success and rescue rates for our ambulatory measurements and quantified heterogeneity using a mixed-effects model. We investigated the source of the heterogeneity in both a univariate and multivariate manner with a meta-regression model. Our analysis included data from 24 surgical articles (999 patients) and 4 radiation articles (543 patients), mostly uncontrolled cohort studies (Class III). Surgical patients were 1.3 times more likely to be ambulatory after treatment and twice as likely to regain ambulatory function. Overall ambulatory success rates for surgery and radiation were 85% and 64%, respectively. Primary pathology was the principal factor determining survival. We present the first known formal meta-analysis using data from nonrandomized clinical studies. Although we attempted to control for imbalances between the surgical and radiation groups, significant heterogeneity undoubtedly still exists. Nonetheless, we believe the differences in the outcomes indicate a true difference resulting from treatment. We conclude that surgery should usually be the primary treatment with radiation given as adjuvant therapy. Neurologic status, overall health, extent of disease (spinal and extraspinal), and primary pathology all impact proper treatment selection.
296 citations
TL;DR: A trend toward progressive centralization of craniotomies for primary brain tumor toward large-volume US centers during this interval is suggested, particularly in relation to provider caseload.
Abstract: Contemporary reports of patient outcomes after biopsy or resection of primary brain tumors typically reflect results at specialized centers. Such reports may not be representative of practices in nonspecialized settings. This analysis uses a nationwide hospital discharge database to examine trends in mortality and outcome at hospital discharge in 38,028 admissions for biopsy or resection of supratentorial primary brain tumors in adults between 1988 and 2000, particularly in relation to provider caseload. Multivariate analyses showed that large-volume centers had lower in-hospital postoperative mortality rates than centers with lighter caseloads, both for craniotomies (odds ratio [OR] 0.75 for a tenfold larger caseload) and for needle (closed) biopsies (OR 0.54). Adverse discharge disposition was also less likely at high-volume hospitals, both for craniotomies (OR 0.77) and for needle biopsies (OR 0.67). The annual number of surgical admissions increased by 53% during the 12-year study period, and in-hospital mortality rates decreased during this period, from 4.8% to 1.8%. Mortality rates decreased over time, both for craniotomies and for needle biopsies. Subgroup analyses showed larger relative mortality rate reductions at large-volume centers than at small-volume centers (73% vs. 43%, respectively). The number of U.S. hospitals performing one or more craniotomies annually for primary brain tumors decreased slightly, and the number performing needle biopsies increased. There was little change in median hospital annual craniotomy caseloads, but the largest centers had disproportionate growth in volume. The 100 highest-caseload U.S. hospitals accounted for an estimated 30% of the total U.S. surgical primary brain tumor caseload in 1988 and 41% in 2000. Our findings do not establish minimum volume thresholds for acceptable surgical care of primary brain tumors. However, they do suggest a trend toward progressive centralization of craniotomies for primary brain tumor toward large-volume U.S. centers during this interval.
151 citations
TL;DR: Volumetric monitoring of brain development can be used to guide the care of survivors, assess the toxicity of previous and current clinical trials, and aid in the design of therapies that minimize toxicity.
Abstract: Brain tumors constitute approximately 20% of pediatric malignancies. Because of the inherent risk of these tumors, patients receive aggressive CNS therapy that often comprises maximal surgical resection, local and craniospinal irradiation (CSI), and adjuvant chemotherapy. Consequently, long-term survivors are at risk of cognitive delays or deficits that impair their academic performance, employment opportunities, and quality of life (Dennis et al., 1996; Mulhern et al., 1998; Ris et al., 2001).
In survivors of childhood medulloblastoma (MB), deficits in IQ and academic achievement appear to reflect a diminished ability to acquire new information (Palmer et al., 2001). One or more cognitive processing mechanisms, including attention, short-term memory, speed of processing, visual-motor coordination, and sequencing ability, may be impaired (Schatz et al., 2000). These processes depend on the integrity of widely distributed neural networks supported by interhemispheric and intrahemispheric white matter tracts. Recent findings have shown that in pediatric patients treated for brain tumors, a reduced volume of normal-appearing white matter (NAWM)3 is associated with reduced attentional ability and a decline in IQ and academic achievement (Reddick et al., 2003).
The proportion of intracranial volume that is NAWM is normally expected to increase into early adulthood. This increase is usually modeled as a quadratic function in which growth is most rapid in the first five years, continues to rise at a moderate rate over the next 10 years, and then slows to asymptotically approach the adult volume (Giedd et al., 1999; Sowell et al., 2002). Previous studies of the association between NAWM and cognitive function have yielded mixed results (Andreasen et al., 1993; Reiss et al., 1996). NAWM volume is not strongly related to IQ in healthy children but is significantly associated in other populations with pathological conditions such as attention deficit-hyperactivity disorder (Castellanos et al., 2002). At least one author has suggested a threshold effect in which cognitive impairment becomes apparent only below a certain volume of NAWM (Inzitari, 2000).
Studies that have quantified toxic effects on white matter and investigated the association between neurotoxicity and cognitive deficits in children have focused primarily on survivors of MB of the posterior fossa (approximately 20% of pediatric brain tumors). One such study compared patients treated for MB with age-similar controls who had received surgery alone for low-grade tumors of the posterior fossa; the survivors of MB had a significantly smaller volume of NAWM, a substantially greater volume of cerebrospinal fluid (CSF), and an equal volume of gray matter (Reddick et al., 1998). This study also demonstrated that chemotherapy did not have a significant detectable impact on tissue volumes. The MB patients also had significantly lower IQs (Mulhern et al., 1999). However, because of their cross-sectional design, these studies could not discern whether the smaller NAWM volume reflected loss of tissue, decreased myelination, or both. A subsequent longitudinal study revealed a significant loss of NAWM volume in patients undergoing treatment for MB; this loss was more rapid among patients who received a CSI dose of 36 Gy versus CSI of 23.4 Gy (Reddick et al., 2000). However, this study was limited by a relatively short median follow-up period of one year.
NAWM volume can explain approximately 70% of the association between IQ impairment and age at the time of irradiation (Mulhern et al., 2001). In a recent cross-sectional study, patients treated for MB showed significantly impaired performance on all neurocognitive measures of intellect, attention, memory, and academic achievement (Reddick et al., 2003). The study produced a developmental model in which academic achievement was predicted by NAWM volume, attentional ability, and IQ; these factors explained approximately 60% of the variance observed in reading and spelling and almost 80% of the variance observed in mathematics. The primary consequence of reduced NAWM volume was decreased attentional ability, which reduced patients’ IQ and academic achievement (Reddick et al., 2003).
We designed a retrospective longitudinal study to compare brain volume development of patients treated for MB with that of healthy, age-similar peers. To control for the effect of irradiation dose, we included only patients who received a CSI dose of 35 to 40 Gy (once used to treat all cases of MB and now used for patients at high risk). This retrospective design has three limitations that could conceivably cause results to differ from more comprehensive prospective trials: (1) Imaging was limited to a single representative section, (2) diffusion tensor imaging was not acquired as a routine part of clinical imaging during this period, and (3) extent and incidence of regions of T2 hyperintensity in other locations could not be assessed by the single index section. However, this retrospective study was designed to comprise as homogeneous a group of subjects as possible: Patients received similar doses of CSI to treat the same type of tumor, which arose in the same location. This study builds on previous work by including serial magnetic resonance (MR) studies to determine the effect of age at irradiation, time since irradiation, gender, use of chemotherapy, and use of ventricular shunt on the development of brain parenchyma (Reddick et al., 1998).
128 citations
TL;DR: It is concluded that the 4C8/B6D2F1 syngeneic glioma model is suitable for preclinical evaluation of HSV-based therapies and that M002 is a superior virus for the treatment of murineglioma in this model.
Abstract: Long-term survivors of glioblastoma multiforme, the most common form of primary intracranial malignancy in adults, are extremely rare. Experimental animal models that more closely resemble human disease are essential for the identification of effective novel therapies. We report here an extensive analysis of the 4C8 glioma model to assess its suitability for evaluating novel type 1 herpes simplex virus (HSV-1) therapies of malignant glioma. We first determined that expression of major histocompatibility complex I and II and of αvβ3 in the 4C8 model was comparable to that seen in human glioma cells. Next, using a panel of Δγ134.5 HSVs, we demonstrated that, in vitro, 4C8 cells were as sensitive as human glioma cells to both infection and lysis and that the 4C8 cells supported the production of foreign gene products. Replication competence of HSV was demonstrated in vitro. Finally, 4C8 intracranial gliomas were established in immunologically competent syngeneic B6D2F1 mice, treated by intratumoral injection of selected engineered HSVs, including the interleukin-12-expressing virus, M002. Survival data from these studies demonstrated that 4C8 cells in vivo are sensitive to both direct oncolysis and HSV-mediated interleukin-12 expression. Fluorescence-activated cell sorting analyses of immune-related infiltrating cells supported the concept that survival was prolonged in part because of antitumor actions of these cells. We conclude that the 4C8/B6D2F1 syngeneic glioma model is suitable for preclinical evaluation of HSV-based therapies and that M002 is a superior virus for the treatment of murine glioma in this model.
116 citations
TL;DR: Infusion of LY341495 to the cultures reduced cell growth, expression of cyclin D1/2, and activation of the MAP kinase and phosphatidylinositol-3-kinase pathways, in line with the evidence that activation of mGlu2/3 receptors sustains glioma cell proliferation.
Abstract: U87MG human glioma cells in cultures expressed metabotropic glutamate (mGlu) receptors mGlu2 and mGlu3. Addition of the mGlu2/3 receptor antagonist LY341495 to the cultures reduced cell growth, expression of cyclin D1/2, and activation of the MAP kinase and phosphatidylinositol-3-kinase pathways. This is in line with the evidence that activation of mGlu2/3 receptors sustains glioma cell proliferation. U87MG cells were either implanted under the skin (1 × 106 cells/0.5 ml) or infused into the caudate nucleus (0.5 × 106 cells/5 μl) of nude mice. Animals were treated for 28 days with mGlu receptor antagonists by means of subcutaneous osmotic minipumps. Treatments with LY341495 or (2S)-α-ethylglutamate (both infused at a rate of 1 mg/kg per day) reduced the size of tumors growing under the skin. Infusion of LY341495 (10 mg/kg per day) also reduced the growth of brain tumors, as assessed by magnetic resonance imaging analysis carried out every seven days. The effect of drug treatment was particularly evident during the exponential phase of tumor growth, that is, between the third and the fourth week following cell implantation. Immunohistochemical analysis showed that U87MG cells retained the expression of mGlu2/3 receptors when implanted into the brain of nude mice. These data suggest that mGlu2/3 receptor antagonists are of potential use in the experimental treatment of malignant gliomas.
110 citations
TL;DR: Although serum copper was effectively reduced by diet and penicillamine, this antiangiogenesis strategy did not improve survival in patients with glioblastoma multiforme.
Abstract: Penicillamine is an oral agent used to treat intracerebral copper overload in Wilson’s disease. Copper is a known regulator of angiogenesis; copper reduction inhibits experimental glioma growth and invasiveness. This study examined the feasibility, safety, and efficacy of creating a copper deficiency in human glioblastoma multiforme. Forty eligible patients with newly diagnosed glioblastoma multiforme began radiation therapy (6000 cGy in 30 fractions) in conjunction with a low-copper diet and escalating doses of penicillamine. Serum copper was measured at baseline and monthly. The primary end point of this study was overall survival compared to historical controls within the NABTT CNS Consortium database. The 25 males and 15 females who were enrolled had a median age of 54 years and a median Karnofsky performance status of 90. Surgical resection was performed in 83% of these patients. Normal serum copper levels at baseline (median, 130 μg/dl; range, 50–227 μg/dl) fell to the target range of <50 μg/dl (median, 42 μg/dl; range, 12–118 μg/dl) after two months. Penicillamine-induced hypocupremia was well tolerated for months. Drug-related myelosuppression, elevated liver function tests, and skin rash rapidly reversed with copper repletion. Median survival was 11.3 months, and progression-free survival was 7.1 months. Achievement of hypocupremia did not significantly increase survival. Although serum copper was effectively reduced by diet and penicillamine, this antiangiogenesis strategy did not improve survival in patients with glioblastoma multiforme.
TL;DR: The extent to which NSCs infiltrate three-dimensional glioma cell aggregates appears to depend on additional factors, which are likely to include cell-to-cell contacts and interaction with extracellular matrix proteins.
Abstract: Various in vivo studies demonstrated a migration tendency of neural stem cells (NSCs) toward gliomas, making these cells a potential carrier for delivery of therapeutic genes to disseminated glioma cells. We analyzed which factors determine NSC migration and invasion in vitro. Conditioned media prepared from 10 different human glioma cell lines, as well as 13 different tumor-associated growth factors, were analyzed for their chemotactic effects on murine C17.2 NSCs. The growth factor receptor status was analyzed by reverse transcriptase–polymerase chain reaction. Invasion of NSCs into multicellular tumor spheroids generated from 10 glioma cell lines was quantified. NSCs displayed a heterogeneous migration pattern toward glioma spheroids as well as toward glioma-cell-conditioned medium. Chemotactic migration was stimulated up to fivefold by conditioned medium as compared to controls. In coculture assays, NSC invasion varied from single cell invasion into glioma spheroids to complete dissemination of NSCs into glioma spheroids of different cell lines. Among 13 different growth factors, scatter factor/hepatocyte growth factor (SF/HGF) was the most powerful chemoattractant for NSCs, inducing a 2.5-fold migration stimulation. An antibody against SF/HGF inhibited migratory stimulation induced by conditioned media. NSC migration can be stimulated by various growth factors, similar to glioma cell migration. The extent to which NSCs infiltrate three-dimensional glioma cell aggregates appears to depend on additional factors, which are likely to include cell-to-cell contacts and interaction with extracellular matrix proteins.
TL;DR: Evidence suggests that expression of specific endogenous inhibitors of angiogenesis in certain organs may be part of a host antitumor response, and suggests that new antiangiogenic therapies for malignant gliomas offer exciting promise as nontoxic, growth-inhibitory agents.
Abstract: Angiogenesis is necessary for tumor growth beyond a volume of approximately 2 mm(3). This observation, along with the accessibility of tumor vessels to therapeutic targeting, has resulted in a research focus on inhibitors of angiogenesis. A number of endogenous inhibitors of angiogenesis are found in the body. Some of these are synthesized by specific cells in different organs, and others are created by extracellular proteolytic cleavage of plasma-derived or extracellular matrix-localized proteins. In this review, we focus on angiostatin, endostatin, PEX, pigment epithelial-derived factor, and thrombospondin (TSP)-1 and -2, either because these molecules are expressed in malignant glioma biopsies or because animal studies in malignant glioma models have suggested that their therapeutic administration could be efficacious. We review the known mechanisms of action, potential receptors, expression in glioma biopsy samples, and studies testing their potential therapeutic efficacy in animal models of malignant glioma. Two conclusions can be made regarding the mechanisms of action of these inhibitors: (1) Several of these inhibitors appear to mediate their antiangiogenic effect through multiple protein-protein interactions that inhibit the function of proangiogenic molecules rather than through a specific receptor-mediated signaling event, and (2) TSP-1 and TSP-2 appear to mediate their antiangiogenic effect, at least in part, through a specific receptor, CD36, which initiates the antiangiogenic signal. Although not proven in gliomas, evidence suggests that expression of specific endogenous inhibitors of angiogenesis in certain organs may be part of a host antitumor response. The studies reviewed here suggest that new antiangiogenic therapies for malignant gliomas offer exciting promise as nontoxic, growth-inhibitory agents.
TL;DR: The MTD and recommended phase 2 dose of PB is defined at 27 g/day for heavily pretreated patients with recurrent gliomas and the pharmacology of PB appears to be affected by concomitant administration of P450-inducing anticonvulsants.
Abstract: Differentiating agents may alter tumor growth and progression, slow or inhibit metastases, and/or affect response to other forms of therapy. Phenyl-butyrate (PB)4 is an aromatic fatty acid that is converted in vivo to phenylacetate (PA) by β-oxidation in liver and kidney mitochondria. The actions of PB as a differentiating agent are primarily related to its activity as an inhibitor of histone deacetylase (Carducci et al., 1996). In vitro PB concentrations required to inhibit histone deacetylase and induce apoptosis begin at 0.5 mM of PB. In solid tumor cell lines, PB induces G1/G0 arrest and induces p21waf1/cip1, a cell cycle checkpoint protein associated with differentiation and an inhibitor of histone deacetylase, within 24 h of treatment. Glioblastoma and prostate cancer cell lines exposed to PA and PB (Gore et al., 2002) at concentrations of 1 to 5 mM in vitro develop time-and dose-dependent growth arrest (Dmitrovsky et al., 1990; Samid et al., 1993). Human glioblastoma cells can undergo cell maturation and revert to a nonmalignant phenotype when exposed to these agents (Dmitrovsky et al., 1990; Hudgins et al., 1994; Sidell et al., 1995). In vivo studies exist for experimental gliomas in rats. Samid and colleagues administered PA to rats bearing intracranial glioma cells and showed suppression of tumor growth, more than 50% of the animals being rendered free of tumor when exposed to continuously administered PA (Samid et al., 1994). Phenylbutyrate had not been tested in these glioma models, but as a precursor in PA, and as a more potent agent, clinical studies of PB were warranted.
A phase 1 clinical trial of continuous intravenous infusions of PB in patients with refractory solid tumors demonstrated that this agent is safe and that doses of 410 mg/kg per day for five days every 21 days are well tolerated (Carducci et al., 2001). No complete responses (CRs) were noted; however, one patient with prostate cancer did have a partial response (PR). The dose-limiting toxicity (DLT) in this study was predominantly neurocortical. A phase 1 study of oral PB in 28 patients with solid tumors also showed that this agent was well tolerated. Oral bioavailability was 78%, and the maximum tolerated dose (MTD) was 27 g/day, with nausea/vomiting, neurocortical toxicity, and hypocalcemia being dose limiting at doses ⩾45 g/day (Gilbert et al., 2001). Both of these studies excluded patients with primary CNS tumors.
This study was designed to evaluate the safety, toxicity, and pharmacology of orally administered PB given three times daily to patients with recurrent high-grade gliomas until progression. In this clinical trial, we also studied the tolerability of continued exposure to oral PB, the ability to achieve plasma levels of >0.5 mM, and the impact of P450-inducing anticonvulsant drugs on the pharmacology of PB and its metabolites, and we examined preliminary evidence of therapeutic activity.
TL;DR: The results demonstrate that CA IX and XII are upregulated in intrinsic and metastatic brain tumors as compared to normal brain tissue, which may contribute to the management of tumor-specific acid load and provide a therapeutic target.
Abstract: Malignant brain tumors exhibit distinct metabolic characteristics. Despite high levels of lactate, the intracellular pH of brain tumors is more alkaline than normal brain. Additionally, with increasing malignancy, brain tumors display intratumoral hypoxia. Carbonic anhydrase (CA) IX and XII are transmembrane isoenzymes that are induced by tissue hypoxia. They participate in regulation of pH homeostasis by catalyzing the reversible hydration of carbon dioxide. The aim of our study was to investigate whether brain tumors of different histology and grade of malignancy express elevated levels of CA IX and XII as compared to normal brain. We analyzed 120 tissue specimens from brain tumors (primary and metastatic) and normal brain for CA IX and XII expression by immunohistochemistry, Western blot, and in situ hybridization. Whereas normal brain tissue showed minimal levels of CA IX and XII expression, expression in tumors was found to be upregulated with increased level of malignancy. Hemangioblastomas, from patients with von Hippel-Lindau disease, also displayed high levels of CA IX and XII expression. Comparison of CA IX and XII staining with HIF-1alpha staining revealed a similar microanatomical distribution, indicating hypoxia as a major, but not the only, induction factor. The extent of CA IX and XII staining correlated with cell proliferation, as indicated by Ki67 labeling. The results demonstrate that CA IX and XII are upregulated in intrinsic and metastatic brain tumors as compared to normal brain tissue. This may contribute to the management of tumor-specific acid load and provide a therapeutic target.
TL;DR: Genotyped constitutive variants ERCC1 C8092A and ERCC2 K751Q and R156R in approximately 450 adults with glioma and 500 controls from two independent population-based series, uniformly reviewed patients' tumors to determine histopathologic category, and determined a variety of tumor markers among astrocytic tumors.
Abstract: ERCC2 and ERCC1 are important in DNA nucleotide excision repair and lie on chromosome 19q13.3 near a putative glioma suppressor region. We genotyped constitutive variants ERCC1 C8092A and ERCC2 K751Q and R156R in approximately 450 adults with glioma and 500 controls from two independent population-based series, uniformly reviewed patients’ tumors to determine histopathologic category, and determined a variety of tumor markers among astrocytic tumors. Odds ratios (ORs) for glioblastoma for those carrying two ERCC1 A alleles versus none or one were 1.67 in series 1 and 1.64 in series 2, which yielded a combined OR of 1.67 (95% CI, 0.93–3.02; P = 0.09), adjusted for age, gender, ethnicity, and series. Odds ratios for the ERCC2 variants were not consistently elevated or reduced for the two series in all cases versus controls. However, among whites, for those with ERCC2 K751Q genotype QQ versus QK/KK, the OR for nonglioblastoma histologies versus controls was 1.82 (95% CI, 0.97–3.44; P = 0.06). Also, among whites, glioma patients were significantly more likely than controls to be homozygous for variants in both ERCC1 C8092A and ERCC2 K751Q (OR, 3.2; 95% CI, 1.1–9.3). Given the numbers of comparisons made, these findings could be due to chance. However, the results might warrant clarification in additional series in conjunction with the nearby putative glioma suppressor genes (GLTSCR1 and GLTSCR2)
TL;DR: Two clinical case reports demonstrating profound cerebral edema associated with implantation of Gliadel wafers are shown, one of which had premature death.
Abstract: While the introduction of carmustine wafers (Gliadel wafers) into the tumor resection cavity has been shown to be a beneficial therapy for malignant glioma, it is recognized that clinically significant cerebral edema is a potential adverse effect. Following are two clinical case reports demonstrating profound cerebral edema associated with implantation of Gliadel wafers. As a result, one of these individuals had premature death. A brief literature review is provided to assist in explaining the mechanisms by which clinically significant cerebral edema may develop.
TL;DR: The data demonstrated CTR to be superior to ITR for local control and survival, and application of postoperative radiotherapy should be decided individually, taking into account the risk of local failure, the need for another craniotomy, and potential radiation toxicity.
Abstract: Most neurocytomas are well differentiated, being associated with better long-term survival than the more aggressive atypical lesions. Atypical neurocytomas are characterized by an MIB-1 labeling index >3% or atypical histologic features. This analysis focuses on well-differentiated neurocytomas in order to define the optimal treatment. A case with a follow-up of 132 months is presented. The patient developed two recurrences two and four years after first surgery, each showing an increasing proliferation activity. Furthermore, all published well-differentiated neurocytoma cases were reviewed for surgery, radiotherapy, and prognosis. Additional relevant data were obtained from the authors. Complete resection (CTR), complete resection plus radiotherapy (CTR + RT), incomplete resection (ITR), and incomplete resection plus radiotherapy (ITR + RT) were compared for outcome by using the Kaplan-Meier method and the log-rank test. Data were complete in 301 patients (CTR, 108; CTR + RT, 27; ITR, 81; ITR + RT, 85). Local control and survival were better after CTR than after ITR (P 54 Gy (n = 32) were not significantly different for local control (P = 0.88) and survival (P = 0.95). The data demonstrated CTR to be superior to ITR for local control and survival. After CTR and ITR, radiotherapy improved local control, but not survival. A radiation dose of 54 Gy appeared sufficient. Application of postoperative radiotherapy should be decided individually, taking into account the risk of local failure, the need for another craniotomy, and potential radiation toxicity.
TL;DR: It is shown that flavopiridol treatment of human U87MG and T98G glioma cell lines decreases hypoxia-mediated HIF-1alpha expression, VEGF secretion, and tumor cell migration, and in vitro results correlate with reduced vascularity of intracranial syngeneic GL261 gliomas from animals treated with flavopIRidol.
Abstract: Angiogenesis is a critical step required for sustained tumor growth and tumor progression. The stimulation of endothelial cells by cytokines secreted by tumor cells such as vascular endothelial growth factor (VEGF) induces their proliferation and migration. This is a prominent feature of high-grade gliomas. The secretion of VEGF is greatly upregulated under conditions of hypoxia because of the transcription factor hypoxia-inducible factor (HIF)-1α, which controls the expression of many genes, allowing rapid adaptation of cells to their hypoxic microenvironment. Flavopiridol, a novel cyclin-dependent kinase inhibitor, has been attributed with antiangiogenic properties in some cancer cell lines by its ability to inhibit VEGF production. Here, we show that flavopiridol treatment of human U87MG and T98G glioma cell lines decreases hypoxia-mediated HIF-1α expression, VEGF secretion, and tumor cell migration. These in vitro results correlate with reduced vascularity of intracranial syngeneic GL261 gliomas from animals treated with flavopiridol. In addition, we show that flavopiridol downregulates HIF-1α expression in the presence of a proteasome inhibitor, an agent that normally results in the accumulation and overexpression of HIF-1α. The potential to downregulate HIF-1α expression with flavopiridol treatment in combination with a proteasome inhibitor makes this an extremely attractive anticancer treatment strategy for tumors with high angiogenic activity, such as gliomas.
TL;DR: Large patient numbers and long follow-up demonstrate that local relapse rates for spinal ependymomas are higher than previously cited, with a large proportion of failures occurring more than 5 years after diagnosis, and it is recommended to recommend excision aimed at maximal resection while avoiding surgical morbidity.
Abstract: Data on spinal ependymomas are sparse, and prognostic factors remain controversial. The primary aim of this study is to review a historical cohort, with large patient numbers and long follow-up, and provide estimates of time to progression (TTP) and survival after progression. As a secondary aim, we assess the effects of potential prognostic variables. Thirty-seven patients with spinal cord ependymomas received postoperative radiation therapy from 1955 to 2001. The influences of radiation dose, extent of resection, Karnofsky performance score, tumor location, and multifocality were assessed in univariate analyses by using the Cox proportional hazards model. The median follow-up for patients who did not fail was 121 months (range, 8-312 months). Kaplan-Meier estimates of 5-, 10-, and 15-year percentage progression free are 75%+/-7.4%, 50%+/-9.1%, and 46%+/-9.3%, respectively. Median TTP, for those who recurred, is 68 months (range, 2-324 months), with 12 of 21 failures occurring after five years. Of the prognostic factors examined, only greater extent of resection significantly correlated with longer TTP (P=0.02). Local relapse rates for spinal ependymomas are higher than previously cited, with a large proportion of failures occurring more than five years after diagnosis. Extensive surgical resection correlates with longer time to recurrence, and we thus recommend maximal excision while avoiding surgical morbidity. The overall high rate of recurrence leads us to recommend radiation to doses of 45 to 54 Gy for all patients who do not have gross total resections, and long, close follow-up.
TL;DR: To the authors' knowledge, this is the first time microarray analysis and Q-PCR have been linked to identify heterozygous/homozygous deletions in ependymoma tumorigenesis.
Abstract: Ependymomas are glial cell-derived tumors characterized by varying degrees of chromosomal abnormalities and variability in clinical behavior. Cytogenetic analy-sis of pediatric ependymoma has failed to identify consistent patterns of abnormalities, with the exception of monosomy of 22 or structural abnormalities of 22q. In this study, a total of 19 pediatric ependymoma samples were used in a series of expression profiling, quantitative real-time PCR (Q-PCR), and loss of heterozygosity experiments to identify candidate genes involved in the development of this type of pediatric malignancy. Of the 12,627 genes analyzed, a subset of 112 genes emerged as being abnormally expressed when compared to three normal brain controls. Genes with increased expression included the oncogene WNT5A; the p53 homologue p63; and several cell cycle, cell adhesion, and proliferation genes. Underexpressed genes comprised the NF2 interact-ing gene SCHIP-1 and the adenomatous polyposis coli (APC)-associated gene EB1 among others. We validated the abnormal expression of six of these genes by Q-PCR. The subset of differentially expressed genes also included four underexpressed transcripts mapping to 22q12.3-13.3. By Q-PCR we show that one of these genes, CBX7 (22q13.1), was deleted in 55% of cases. Other genes mapping to cytogenetic hot spots included two overexpressed and three underexpressed genes mapping to 1q31-41 and 6q21-q24.3, respectively. These genes represent candidate genes involved in ependymoma tumorigenesis. To the authors' knowledge, this is the first time microarray analysis and Q-PCR have been linked to identify heterozygous/homozygous deletions.
TL;DR: This study quantified the expression of four genes that were putative prognostic markers in a set of 43 AAs, 41 GBMs, and seven adjacent normal brain tissues to establish a prognostic model that accounted for two thirds of the variation in survival for this set of patients and demonstrated that incorporating genes from different pathways markedly strengthens the model.
Abstract: The disparate lengths of survival among patients with malignant astrocytic gliomas (anaplastic astrocytomas [AAs] and glioblastoma multiforme [GBM]) cannot be adequately accounted for by clinical variables (patient age, histology, and recurrent status). Using real-time quantitative reverse transcription-polymerase chain reaction, we quantified the expression of four genes that were putative prognostic markers (CDK4, IGFBP2, MMP2, and RPS9) in a set of 43 AAs, 41 GBMs, and seven adjacent normal brain tissues. We previously explicated the expression and prognostic value of PAX6, PTEN, VEGF, and EGFR in these glioma tissues and established a comprehensive prognostic model (Zhou et al., 2003). This study attempts to improve that model by including four additional genetic markers, which exhibited a differential expression (P < 0.001) among tumor grades and between tumor and normal tissues. By including eight log-scaled gene expression variables, three clinical variables, and interaction terms among the eight genes, we established a prognostic model that accounted for two thirds of the variation (R2) in survival for this set of patients. To improve the R2 of the model without compromising its clinical utility, our data demonstrated that incorporating genes from different pathways markedly strengthens the model. Spearman rank correlation analysis of gene expression demonstrated a statistically significant positive correlation (P < 0.01) between the expression of IGFBP2-MMP2 and IGFBP2-VEGF in GBMs, but not in AAs. This finding suggests that the expression of IGFBP2 is associated with pathways activated specifically in GBMs that result in enhancing invasiveness and angiogenesis.
TL;DR: This is the first study to use an antisense oligonucleotide or a specific PKC-alpha inhibitor in patients with high-grade gliomas by continuous intravenous infusion and no clinical benefit was seen.
Abstract: Protein kinase C alpha (PKC-α) is a cytoplasmic serine threonine kinase involved in regulating cell differentiation and proliferation. Aprinocarsen is an antisense oligonucleotide against PKC-α that reduces PKC-α in human cell lines and inhibits a human glioblastoma tumor cell line in athymic mice. In this phase 2 study, aprinocarsen was administered to patients with recurrent high-grade gliomas by continuous intravenous infusion (2.0 mg/kg/day for 21 days per month). Twenty-one patients entered this trial. Their median age was 46 years (range, 28–68 years), median Karnofsky performance status was 80 (range, 60–100), median tumor volume was 58 cm3 (range, 16–254 cm3), and histology included glioblastoma multiforme (n = 16), anaplastic oligodendroglioma (n = 4), and anaplastic astrocytoma (n = 1). The number of prior chemotherapy regimens included none (n = 3), one (n = 10), and two (n = 8). No tumor responses were observed. Patients on this therapy rapidly developed symptoms of increased intracranial pressure with increased edema, enhancement, and mass effect on neuroimaging. The median time to progression was 36 days, and median survival was 3.4 months. The observed toxicities were mild, reversible, and uncommon (grade 3 thrombocytopenia [n = 3] and grade 4 AST [n = 1]), and no coagulopathy or CNS bleeding resulted from this therapy. Plasma concentrations of aprinocarsen during the infusion exhibited significant interpatient variability (mean = 1.06 μg/ml; range, 0.34–6.08 μg/ml). This is the first study to use an antisense oligonucleotide or a specific PKC-α inhibitor in patients with high-grade gliomas. No clinical benefit was seen. The rapid deterioration seen in these patients could result from tumor growth or an effect of aprinocarsen on blood-brain barrier integrity.
TL;DR: A relative dearth of research devoted to chaperone protein targets and therapeutics in brain tumors reveals much untrodden turf to explore for potential treatments of these dreadfully refractive diseases.
Abstract: Chaperone proteins are most notable for the proteo- and cyotoprotective capacities they afford during cellular stress. Under conditions of cellular normalcy, chaperones still play integral roles in the folding of nascent polypeptides into functional entities, in assisting in intracellular/intraorganellar transport, in assembly and maintenance of multi-subunit protein complexes, and in aiding and abetting the degradation of senescent proteins. Tumors frequently have relatively enhanced needs for chaperone number and activity because of the stresses of rapid proliferation, increased metabolism, and overall genetic instability. Thus, it may be possible to take advantage of this reliance that tumor cells have on chaperones by pharmacologic and biologic means. Certain chaperones are abundant in the brain, which implies important roles for them. While it is presumed that the requirements of brain tumors for chaperone proteins are similar to those of any other cell type, tumor or otherwise, very little inquiry has been directed at the possibility of using chaperone proteins as therapeutic targets or even as therapeutic agents against central nervous system malignancies. This review highlights some of the research on the functions of chaperone proteins, on what can be done to modify those functions, and on the physiological responses that tumors and organisms can have to chaperone-targeted or chaperone-based therapies. In particular, this review will also underscore areas of research where brain tumors have been part of the field, although in general those instances are few and far between. This relative dearth of research devoted to chaperone protein targets and therapeutics in brain tumors reveals much untrodden turf to explore for potential treatments of these dreadfully refractive diseases.
TL;DR: Sequential and high-dose chemotherapy can be afforded in front-line therapy of childhood malignant glioma without excessive morbidity and rather encouraging results.
Abstract: Childhood malignant gliomas are rare, but their clinical behavior is almost as aggressive as in adults, with resistance to therapy, rapid progression, and not uncommonly, dissemination. Our study protocol incorporated sequential chemotherapy and high-dose thiotepa in the preradiant phase, followed by focal radiotherapy and maintenance with vincristine and lomustine for a total duration of one year. The induction treatment consisted of two courses of cisplatin (30 mg/m2) plus etoposide (150 mg/m2) × 3 days and of vincristine (1.4 mg/m2) plus cyclophosphamide (1.5 g/m2) plus high-dose methotrexate (8 g/m2), followed by high-dose thiotepa (300 mg/m2 × 3 doses), with harvesting of peripheral blood progenitor cells after the first cisplatin/etoposide course. From August 1996 to March 2003, 21 children, 14 females and 7 males, with a median age of 10 years were enrolled, 18 presenting with residual disease after surgery. Histologies were glioblastoma multiforme in 10, anaplastic astrocytoma in nine, and anaplastic oligodendroglioma in two; sites of origin were supratentorial areas in 17, spine in two, and posterior fossa in two. Of the 21 patients, 12 have died (10 after relapse, with a median time to progression for the whole series of 14 months; one with intratumoral bleeding at 40 months after diagnosis; and one affected by Turcot syndrome for duodenal cancer relapse). Four of 12 relapsed children had tumor dissemination. At a median follow-up of 57 months, overall survival and progression-free survival at four years were 43% and 46%, respectively. Sequential and high-dose chemotherapy can be afforded in front-line therapy of childhood malignant glioma without excessive morbidity and rather encouraging results.
TL;DR: A dramatic and sustained clinical and radiographic response in a patient with a bifrontal glioblastoma multiforme treated with intratumoral infusion of a novel targeted toxin, TP-38 is described.
Abstract: Glioblastoma multiforme remains refractory to conventional therapy, and novel therapeutic modalities are desperately needed. TP-38 is a recombinant chimeric protein containing a genetically engineered form of the cytotoxic Pseudomonas exotoxin fused to transforming growth factor (TGF)-α. TGF-α binds with high affinity to the epidermal growth factor receptor, which is uniformly overexpressed in malignant gliomas, often because of gene amplification. Prior to therapy with TP-38, the patient described here was completely refractory to multiple other therapies, with radiographic and pathologic evidence of tumor progression. After therapy, she improved clinically, was weaned off steroids and anticonvulsants, and experienced a progressive decrease in enhancing tumor volume. Despite multiple prior recurrences, she has not progressed for >43 months after TP-38 therapy. Small remaining areas of enhancement demonstrate no evidence of tumor histologically and are hypometabolic on positron emission tomography. This report describes a dramatic and sustained clinical and radiographic response in a patient with a bifrontal glioblastoma multiforme treated with intratumoral infusion of a novel targeted toxin, TP-38.
TL;DR: Multidisciplinary consensus was reached on four points, for which the following recommendations were made: amend the histology coding scheme for cysts and tumor-like lesions that currently have a code in the third edition of the International Classification of Disease for Oncology (ICDO).
Abstract: The passage of Public Law 107-260, the Benign Brain Tumor Cancer Registries Amendment Act, in October 2002 has made the collection of all primary brain tumors a reality. However, at the first Consensus Conference on Brain Tumor Definition for Registration in 2002, and during the development of training materials for benign brain tumor collection, several issues were identified that were tabled for future discussion. These and other issues were addressed at the subsequent 2003 Consensus Conference on Cancer Registration of Brain and Central Nervous System Tumors, at which the Central Brain Tumor Registry of the United States facilitated a discussion among epidemiologists, neurosurgeons, and neuropathologists. Multidisciplinary consensus was reached on four points, for which the following recommendations were made: (1) amend the histology coding scheme for cysts and tumor-like lesions that currently have a code in the third edition of the International Classification of Disease for Oncology (ICDO), (2) collect data on all instances of specific cysts and tumor-like lesions that are located in brain and other CNS sites but currently lack ICDO codes, (3) establish a new ICDO topography site for skull base tumors for the brain and CNS, and (4) collect data on genetic syndromes in patients diagnosed with brain or CNS tumors. We view this conference as part of a continuing process. Because classification of primary intracranial and other CNS tumors is dynamic, and the registration and coding of these tumors will need to be periodically reviewed.
TL;DR: It is concluded that despite high TMZ drug acquisition costs, care of recurrent malignant gliomas is comparable to other accepted therapies.
Abstract: Effectiveness and costs of care and treatment of recurrent malignant gliomas are largely unknown. In this study, 49 patients (32 males, 17 females; mean age, 49; age range, 23-79) were treated with temozolomide (TMZ) for recurrent or progressive malignant gliomas after standard radiation therapy. Cost assessment (payer's perspective) singled out treatment for first recurrence and all costs of care until death. We computed personnel costs as wages; drugs, imaging, and laboratory tests as prices; and hospitalizations as day rates. Patients were administered a median of five TMZ cycles at recurrence. Drug acquisition costs amounted to euro 2206 per cycle (76% of total costs). Seven patients showed no second recurrence (two are still alive), 16 received no further chemotherapy and died after 3.9 months, and 26 received second-line chemotherapy. After the second progression, median survival was 4.0 months (95% confidence interval, 1.8-6.1). Overall monthly costs of care varied between euro 2450 and euro 3242 among the different groups, and median cost-effectiveness and cost utility ranged from euro 28,817 to euro 38,450 and from euro 41,167 to euro 53,369 per life of year and per quality-adjusted life-year gained, respectively. We conclude that despite high TMZ drug acquisition costs, care of recurrent malignant gliomas is comparable to other accepted therapies.
TL;DR: The findings demonstrate that the complex operational mechanisms of rapamycin against gliomas include cytostasis, anti-VEGF, and anti-invasion activity, but these are dependent on the in vivo location of the tumor and have implications for the design of a clinical trial.
Abstract: Rapamycin has previously been shown to be efficacious against intracerebral glioma xenografts and to act in a cytostatic manner against gliomas. However, very little is known about the mechanism of action of rapamycin. The purpose of our study was to further investigate the in vitro and in vivo mechanisms of action of rapamycin, to elucidate molecular end points that may be applicable for investigation in a clinical trial, and to examine potential mechanisms of treatment failure. In the phosphatase and tensin homolog deleted from chromosome 10 (PTEN)-null glioma cell lines U-87 and D-54, but not the oligodendroglioma cell line HOG (PTEN null), doses of rapamycin at the IC50 resulted in accumulation of cells in G1, with a corresponding decrease in the fraction of cells traversing the S phase as early as 24 h after dosing. All glioma cell lines tested had markedly diminished production of vascular endothelial growth factor (VEGF) when cultured with rapamycin, even at doses below the IC50. After 48 h of exposure to rapamycin, the glioma cell lines (but not HOG cells) showed downregulation of the membrane type-1 matrix metalloproteinase (MMP) invasion molecule. In U-87 cells, MMP-2 was downregulated, and in D-54 cells, both MMP-2 and MMP-9 were downregulated after treatment with rapamycin. Treatment of established subcutaneous U-87 xenografts in vivo resulted in marked tumor regression (P < 0.05). Immunohistochemical studies of subcutaneous U-87 tumors demonstrated diminished production of VEGF in mice treated with rapamycin. Gelatin zymography showed marked reduction of MMP-2 in the mice with subcutaneous U-87 xenografts that were treated with rapamycin as compared with controls treated with phosphatebuffered saline. In contrast, treatment of established intracerebral U-87 xenografts did not result in increased median survival despite inhibition of the Akt pathway within the tumors. Also, in contrast with our findings for subcutaneous tumors, immunohistochemistry and quantitative Western blot analysis results for intracerebral U-87 xenografts indicated that there is not significant VEGF production, which suggests possible deferential regulation of the hypoxia-inducible factor 1alpha in the intracerebral compartment. These findings demonstrate that the complex operational mechanisms of rapamycin against gliomas include cytostasis, anti-VEGF, and anti-invasion activity, but these are dependent on the in vivo location of the tumor and have implications for the design of a clinical trial.
TL;DR: In this article, the authors present guidelines to standardize the reporting of phase 1 and phase 2 neuro-oncology trials, which are also intended to assist with accurate interpretation of results from these trials, facilitate the peer-review process, and to expedite the publication of important and accurate manuscripts.
Abstract: We present guidelines to standardize the reporting of phase 1 and phase 2 neuro-oncology trials. The guidelines are also intended to assist with accurate interpretation of results from these trials, to facilitate the peer-review process, and to expedite the publication of important and accurate manuscripts. Our guidelines are summarized in a checklist format that can be used as a framework from which to construct a phase 1 or 2 clinical trial.