Mass spectral analysis of organic aerosol formed downwind of the Deepwater Horizon oil spill: field studies and laboratory confirmations.

In June 2010, the NOAA WP-3D aircraft conducted two survey flights around the Deepwater Horizon (DWH) oil spill. The Gulf oil spill resulted in an isolated source of secondary organic aerosol (SOA) precursors in a relatively clean environment. Measurements of aerosol composition and volatile organic species (VOCs) indicated formation of SOA from intermediate-volatility organic compounds (IVOCs) downwind of the oil spill (Science2011, 331, doi 10.1126/science.1200320). In an effort to better understand formation of SOA in this environment, we present mass spectral characteristics of SOA in the Gulf and of SOA formed in the laboratory from evaporated light crude oil. Compared to urban primary organic aerosol, high-mass-resolution analysis of the background-subtracted SOA spectra in the Gulf (for short, "Gulf SOA") showed higher contribution of C(x)H(y)O(+) relative to C(x)H(y)(+) fragments at the same nominal mass. In each transect downwind of the DWH spill site, a gradient in the degree of oxidation of the Gulf SOA was observed: more oxidized SOA (oxygen/carbon = O/C ∼0.4) was observed in the area impacted by fresher oil; less oxidized SOA (O/C ∼0.3), with contribution from fragments with a hydrocarbon backbone, was found in a broader region of more-aged surface oil. Furthermore, in the plumes originating from the more-aged oil, contribution of oxygenated fragments to SOA decreased with downwind distance. Despite differences between experimental conditions in the laboratory and the ambient environment, mass spectra of SOA formed from gas-phase oxidation of crude oil by OH radicals in a smog chamber and a flow tube reactor strongly resembled the mass spectra of Gulf SOA (r(2) > 0.94). Processes that led to the observed Gulf SOA characteristics are also likely to occur in polluted regions where VOCs and IVOCs are coemitted.

Perceptual Deficit during a Mental Task.

Subjects monitored for a visual signal while engaged in a demanding mental task. The probability of detecting the signal depends on the time of its presentation during the 8 seconds of the task. A similar time course is observed for failures to detect and for changes of pupil size. Momentary variations in the load that the task imposes on the subject are reflected in both indices. Detection failures are not explained by the pupillary changes.

Potent topoisomerase I inhibition by novel silatecans eliminates glioma proliferation in vitro and in vivo.

Although topoisomerase inhibitors, such as camptothecin and topotecan, have been widely used in the treatment of nonglial tumors, their application for gliomas has been limited by poor efficacy relative to toxicity that may in part reflect limited bioavailability and blood stability of these agents. However, the potential promise of this class of agents has fostered efforts to develop new, more potent, and less toxic inhibitors that may be clinically relevant. Using a cascade radical annulation route to the camptothecin family, we developed a series of novel camptothecin analogues, 7-silylcamptothecins ("silatecans"), that exhibited potent inhibition of topoisomerase I, dramatically improved blood stability, and sufficient lipophilicity to favor blood-brain barrier transit. We explored the efficacy of a series of these agents against a panel of five high-grade glioma cell lines to identify a promising compound for further preclinical testing. One of the most active agents in our systems (DB67) inhibited tumor growth in vitro with an ED50 ranging between 2 and 40 ng/ml, at least 10-fold more potent than the effects observed with topotecan, and at least comparable with those of SN-38, the active metabolite of CPT-11. Because DB67 also exhibited the highest human blood stability of any of the agents examined, this agent was then selected for in vivo studies. A dose-escalation study of this agent in a nude mouse U87 glioma model system demonstrated a concentration-dependent effect, with tumor growth inhibition at day 28 postimplantation (the day control animals began to require sacrifice because of large tumor size) of 61 +/- 7% and 73 +/- 3% after administration of DB67 doses of 3 and 10 mg/kg/day, respectively, for 5 days beginning on postimplantation day 7. Animals that continued treatment with 10 mg/kg/day in three additional 21-day cycles all remained progression free after >90 days of follow-up but later developed enlarging tumors after treatment was stopped. However, a slightly higher dose (30 mg/kg/day) induced complete tumor regression after only two cycles in all study animals and was effective even if treatment was delayed until large, bulky tumors had developed. Application of the 30 mg/kg/day dose to treat established intracranial glioma xenografts led to long-term (>90 day) survival in six of six animals, whereas all controls died of progressive disease (P < 0.00001). No apparent toxicity was encountered in any of the treated animals. In summary, the present studies indicate that silatecans may hold significant promise for the treatment of high-grade gliomas and provide a rationale for proceeding with further preclinical evaluation of their efficacy and safety versus commercially available camptothecin derivatives.

The relationship between TP53 mutations and overexpression of p53 and prognosis in malignant gliomas of childhood.

The prognosis for children with high-grade gliomas remains somewhat unpredictable. Although prolonged disease control is sometimes achieved after surgery, radiotherapy, and chemotherapy, most patients exhibit rapid disease progression. Because p53-dependent apoptosis mechanisms are involved in the cytotoxic effects of irradiation and chemotherapy, we questioned whether p53 status might be associated with outcome in childhood malignant gliomas. Therefore, we examined p53 status, both immunohistochemically and by direct sequencing of exons 5-8, in a series of 29 archival pediatric malignant non-brainstem gliomas treated consecutively at our institution between 1975 and 1992. Eighteen tumors had dense p53 staining in the majority of cells, although only 11 had mutations of the p53 gene (TP53). On univariate analysis, there was a significant association between p53 overexpression and a shorter progression-free survival (PFS) and overall survival (OS; P = 0.019 and 0.013, respectively; rank sum test). In addition, there was a significant association between TP53 mutations and a poorer PFS (P = 0.04), and a strong trend toward a shorter OS among patients with TP53 mutations (P = 0.06). Median PFS and OS for patients with TP53-mutated tumors were 6 months and 16 months, respectively, and for those with p53 overexpression 5.5 months and 14 months, respectively, versus 16 months and 25 months, respectively, for those without TP53 mutations and 25 months and >4 years, respectively, for those without p53 overexpression. The percentage of patients in this series with TP53 mutations (37.9%) was substantially higher than in previous studies of childhood gliomas and comparable to the frequency of mutations noted in adult gliomas. However, both TP53 mutation and p53 overexpression were significantly less frequent in tumors from children younger than 4 than from older children (P = 0.02 and 0.01, respectively). These results indicate that p53 mutation and expression status may be associated with prognosis in childhood malignant gliomas, and thus may provide a basis for stratifying patients biologically in future malignant glioma studies.

Cytokine gene therapy of gliomas: induction of reactive CD4+ T cells by interleukin-4-transfected 9L gliosarcoma is essential for protective immunity.

Tumor cells genetically modified to secrete cytokines stimulate potent immune responses against peripheral and central nervous system tumors; however, variable results on the efficacy of this strategy for therapeutic intervention against established intracranial neoplasia have been reported. We have found that vaccination with rat 9L gliosarcoma cells expressing interleukin 4 (9LmIL4) induced a specific, protective, immune response against rechallenge with parental 9L tumors. In naive rats, sham-transfected 9L (9Lneo) tumors and 9LmIL4 tumors grew at comparable rates for 12-14 days, and then 9LmIL4 tumors regressed. After regression of 9LmIL4 tumors, rats were resistant to rechallenge with parental 9L cells. To investigate the mechanism(s) responsible for 9LmIL4-induced immunity, the phenotype and function of tumor-infiltrating lymphocytes (TILs) in 9Lneo and 9LmIL4 tumors were compared. In flow cytometric analyses, it was determined that CD4+ T cells were the predominant cell type in both 9Lneo and 9LmIL4 tumors at day 10. However, at the onset of regression (day 14), 9LmIL4 tumors were infiltrated predominantly by CD8+ T cells. To investigate functional aspects of the anti-9L tumor responses, we assessed the capacity of 9LmIL4 TILs to mediate specific lytic function or production of cytokines. In response to parental 9L, TILs isolated from day 14 9LmIL4 tumors were demonstrated to produce substantially greater amounts of IFN-gamma than did TILs from 9Lneo tumors. Although freshly isolated TILs from 9LmIL4 or control tumors did not lyse 9L cells in 51Cr-release cytotoxicity assays, specific cytotoxicity was demonstrable using TILs from day 14 9LmIL4 or splenocytes from 9LmIL4-bearing rats after their restimulation for 5 days with parental 9L tumor cells in vitro. Antibody blocking studies demonstrated that cytokine production and lytic activity by TILs, or splenocytes from 9LmIL4-immunized rats, were mediated in a T-cell receptor-dependent fashion. Because interleukin-4 also promotes humoral responses, quantity and isotype of immunoglobulins in sera from 9Lneo or 9LmIL4-immunized rats were compared. The amount of IgG1 antibodies was significantly increased in sera from 9LmIL4-immunized rats compared to sera from 9Lneo-bearing rats. Experiments using sublethally irradiated, naive rats adoptively transferred with splenocytes and/or sera from 9LmIL4-immunized or naive rats demonstrated that immune cells, with or without immune sera, protected recipients from challenge with parental 9L. Immune sera provided no protection when given with lymphocytes from naive rats, and it did not enhance protection against parental 9L when given in conjunction with lymphocytes for 9LmIL4-immunized rats. In additional adoptive transfer experiments, an essential role for CD4+ T cells in immunity was observed because their depletion from among splenocytes of 9LmIL4-immunized rats eliminated the protective effective against 9L, whereas depletion of CD8+ cells resulted in a more limited effect on protection against 9L. These data suggest that strategies for inducing systemic, long-term tumor-specific reactivity among CD4+ T cells will be critical for the development of immunotherapy of gliomas.

Effect of tamoxifen on DNA synthesis and proliferation of human malignant glioma lines in vitro.

Previous studies in our laboratory have shown that proliferation of human malignant gliomas in vitro depends in part upon the activation of protein kinase C (PKC) and, conversely, can be blocked by inhibitors of PKC. Here, we examined the effect of tamoxifen, a known PKC inhibitor, on DNA synthesis and proliferation of an established human glioma line (U138) and two low passage cultures of explanted human glioblastomas. Tamoxifen produced a profound, dose-dependent inhibition of both [3H] thymidine incorporation and cell proliferation, with a 50% effective dose of 20 ng/ml under serum-free conditions and 50 to 200 ng/ml in the presence of 10% serum. These tumors were estrogen receptor negative and showed no mitogenic response to estradiol. Furthermore, concentrations of estradiol as high as 10 micrograms/ml had no effect on the tamoxifen-induced inhibition. This suggests that the mechanism of growth inhibition by tamoxifen in these gliomas did not involve an estrogen receptor-mediated process but may instead result from its inhibition of PKC. In view of the profound effect of tamoxifen on cultured gliomas at concentrations that can safely be achieved therapeutically, further in vitro and in vivo studies of this agent are warranted.

Age and TP53 mutation frequency in childhood malignant gliomas: results in a multi-institutional cohort.

Malignant astrocytoma is one of the most deadly primary central nervous system tumors. Although significant progress has been made in understanding the molecular pathways that lead to the development of these tumors in adults, comparatively little analysis has been done in childhood astrocytomas, which are less common and have a more favorable prognosis. Our previous studies of an institutional cohort of children with malignant gliomas suggested the existence of distinct molecular pathways of tumorigenesis in younger versus older children, based on the finding of a high frequency of TP53 mutations in tumors from children >3 years of age at diagnosis, compared with those from younger children. In the current study, the association between TP53 mutations and age was examined in greater detail using the multi-institutional group of children enrolled in Children's Cancer Group Study 945, the largest cohort of childhood high-grade gliomas analyzed to date. Seventy-seven tumors with centrally reviewed diagnoses of anaplastic astrocytoma or glioblastoma multiforme had sufficient archival histopathological material for microdissection-based genotyping. Sections were examined histologically, and topographic targets that contained malignant tissue were isolated by microdissection and subjected to PCR-based amplification and sequencing of TP53 exons 5-8. Twenty-six tumors (33.8%) had mutations in those exons. Mutations were observed in 2 of 17 tumors (11.8%) from children <3 years of age at diagnosis versus 24 of 60 tumors (40%) from older children, a difference that was statistically significant (P = 0.04), in agreement with our previous results. Whereas malignant gliomas in older children have a frequency of mutations comparable to tumors that arise in young adults, those from children <3 years old do not. The association between age and frequency of TP53 mutations among pediatric malignant gliomas indicates the probable existence of two distinct pathways of molecular tumorigenesis in younger versus older children.

Formaldehyde production from isoprene oxidation across NOx regimes.

The chemical link between isoprene and formaldehyde (HCHO) is a strong, non-linear function of NOx (= NO + NO2). This relationship is a linchpin for top-down isoprene emission inventory verification from orbital HCHO column observations. It is also a benchmark for overall photochemical mechanism performance with regard to VOC oxidation. Using a comprehensive suite of airborne in situ observations over the Southeast U.S., we quantify HCHO production across the urban-rural spectrum. Analysis of isoprene and its major first-generation oxidation products allows us to define both a "prompt" yield of HCHO (molecules of HCHO produced per molecule of freshly-emitted isoprene) and the background HCHO mixing ratio (from oxidation of longer-lived hydrocarbons). Over the range of observed NOx values (roughly 0.1 - 2 ppbv), the prompt yield increases by a factor of 3 (from 0.3 to 0.9 ppbv ppbv-1), while background HCHO increases by a factor of 2 (from 1.6 to 3.3 ppbv). We apply the same method to evaluate the performance of both a global chemical transport model (AM3) and a measurement-constrained 0-D steady state box model. Both models reproduce the NOx dependence of the prompt HCHO yield, illustrating that models with updated isoprene oxidation mechanisms can adequately capture the link between HCHO and recent isoprene emissions. On the other hand, both models under-estimate background HCHO mixing ratios, suggesting missing HCHO precursors, inadequate representation of later-generation isoprene degradation and/or under-estimated hydroxyl radical concentrations. Detailed process rates from the box model simulation demonstrate a 3-fold increase in HCHO production across the range of observed NOx values, driven by a 100% increase in OH and a 40% increase in branching of organic peroxy radical reactions to produce HCHO.

Instrumentation and Measurement Strategy for the NOAA SENEX Aircraft Campaign as Part of the Southeast Atmosphere Study 2013.

Natural emissions of ozone-and-aerosol-precursor gases such as isoprene and monoterpenes are high in the southeast of the US. In addition, anthropogenic emissions are significant in the Southeast US and summertime photochemistry is rapid. The NOAA-led SENEX (Southeast Nexus) aircraft campaign was one of the major components of the Southeast Atmosphere Study (SAS) and was focused on studying the interactions between biogenic and anthropogenic emissions to form secondary pollutants. During SENEX, the NOAA WP-3D aircraft conducted 20 research flights between 27 May and 10 July 2013 based out of Smyrna, TN. Here we describe the experimental approach, the science goals and early results of the NOAA SENEX campaign. The aircraft, its capabilities and standard measurements are described. The instrument payload is summarized including detection limits, accuracy, precision and time resolutions for all gas-and-aerosol phase instruments. The inter-comparisons of compounds measured with multiple instruments on the NOAA WP-3D are presented and were all within the stated uncertainties, except two of the three NO2 measurements. The SENEX flights included day- and nighttime flights in the Southeast as well as flights over areas with intense shale gas extraction (Marcellus, Fayetteville and Haynesville shale). We present one example flight on 16 June 2013, which was a daytime flight over the Atlanta region, where several crosswind transects of plumes from the city and nearby point sources, such as power plants, paper mills and landfills, were flown. The area around Atlanta has large biogenic isoprene emissions, which provided an excellent case for studying the interactions between biogenic and anthropogenic emissions. In this example flight, chemistry in and outside the Atlanta plumes was observed for several hours after emission. The analysis of this flight showcases the strategies implemented to answer some of the main SENEX science questions.

Phase II study of phenylacetate in patients with recurrent malignant glioma: a North American Brain Tumor Consortium report.

PURPOSE: To determine the response rate, time to treatment failure, and toxicity of phenylacetate in patients with recurrent malignant glioma and to identify plasma concentrations achieved during repeated continuous infusion of this agent. PATIENTS AND METHODS: Adult patients with recurrent malignant glioma were treated with phenylacetate. The schedule consisted of a 2-week continuous, intravenous infusion followed by a 2-week rest period (14 days on, 14 days off). A starting dose of 400 mg/kg total body weight per day of phenylacetate was initially used and subsequently changed to 400 mg/kg/d based on ideal body weight. Intrapatient dose escalations were allowed to a maximum of 450 mg/kg ideal body weight/d. Tumor response was assessed every 8 weeks. The National Cancer Institute common toxicity criteria were used to assess toxicity. Plasma concentrations achieved during the patients' first two 14-day infusions were assessed. RESULTS: Forty-three patients were enrolled between December 1994 and December 1996. Of these, 40 patients were assessable for toxicity and response to therapy. Reversible symptoms of fatigue and somnolence were the primary toxicities, with only mild hematologic toxicity. Thirty (75%) of the 40 patients failed treatment within 2 months, seven (17.5%) had stable disease, and three (7.5%) had a response defined as more than 50% reduction in the tumor. Median time to treatment failure was 2 months. Thirty-five patients have died, with a median survival of 8 months. Pharmacokinetic data for this dose schedule showed no difference in the mean plasma concentrations of phenylacetate between weeks 1 and 2 or between weeks 5 and 6. CONCLUSION: Phenylacetate has little activity at this dose schedule in patients with recurrent malignant glioma. Further studies with this drug would necessitate an evaluation of a different dose schedule.

Phase I study of paclitaxel in patients with recurrent malignant glioma: a North American Brain Tumor Consortium report.

PURPOSE: To determine the maximum-tolerated dose (MTD) of paclitaxel administered as a 3-hour infusion in patients with recurrent malignant glioma. PATIENTS AND METHODS: Patients were stratified by starting dose of paclitaxel and concurrent anticonvulsant (AC) use and were treated in cohorts of three patients. The starting dose was 240 mg/m2 administered intravenously with escalations of 30 mg/m2 until the MTD was established. Pharmacokinetic data were obtained for each patient for the first infusion. Tumor response was assessed at 6-week intervals and treatment was continued until documented tumor progression, unacceptable toxicity, or a total of 12 paclitaxel infusions. RESULTS: From April 1995 to December 1996, 34 patients were treated; 27 patients in the AC group and seven patients in the non-AC group. The MTD for patients who received ACs was established at 360 mg/m2 and the dose-limiting toxicity (DLT) was central neurotoxicity, characterized as transient encephalopathy and seizures. In contrast, the MTD for patients who did not receive ACs was 240 mg/m2, and myelosuppression, gastrointestinal toxicity, and fatigue were the DLTs. Pharmacokinetic data confirmed that the plasma drug levels and clearance rates were similar for patients in both groups at the respective dose levels that produced DLTs. CONCLUSION: The pharmacokinetics of paclitaxel are altered by ACs, and significantly larger doses of the drug can be administered to patients with brain tumors on AC therapy. The toxicity profile is different for patients on AC therapy treated at these higher doses. A phase II study has been initiated that uses a dose of 330 mg/m2 for patients on AC therapy and 210 mg/m2 for patients not on AC therapy.

Direct stimulation of apoptotic signaling by soluble Apo2l/tumor necrosis factor-related apoptosis-inducing ligand leads to selective killing of glioma cells.

Apo2 ligand tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) is a member of the tumor necrosis factor family that interacts with cell surface "death receptors" (DR4 and DR5) to initiate programmed cell death. Apo2L/TRAIL also binds to "decoy" receptors (DcR1 and DcR2) that can antagonize its interaction with DR4 and DR5. In recent studies, Apo2L/TRAIL has been noted to produce selective toxicity toward certain neoplastic cells versus normal cells. The decoy receptors may in part contribute to this selectivity, because they are expressed in various normal tissues but are present at low or undetectable levels in certain types of neoplastic cells. In the current study, we examined the potential therapeutic applicability of recombinant soluble Apo2L/TRAIL by investigating its effects in vitro and in vivo against a series of cell lines derived from malignant gliomas, which are often resistant to conventional treatment modalities. In cell proliferation assays, Apo2L/TRAIL produced a striking decrease in cell numbers, with a median inhibitory concentration of 30-100 ng/ml, in the TP53 wild-type high-grade glioma cell lines U87 and A172, the TP53-mutated T98G, and the TP53-deleted LN-Z308. In contrast, no significant effects were observed in non-neoplastic astrocytes at concentrations up to 3000 ng/ml. Clonogenic assays showed that exposure to Apo2L produced a time-dependent decrease in the viability of glioma-derived cell lines. This correlated with the induction of apoptosis as assessed by a terminal transferase-catalyzed in situ end-labeling assay. Pretreatment of the cells with the caspase inhibitors Acetyl-Asp-Glu-Val-L-aspartic acid aldehyde or Acetyl-Tyr-Val-Ala-Asp-chlormethylketone (200 microM) largely eliminated the effects of Apo2L/TRAIL. Administration of Apo2L/TRAIL (0.3, 1, 3, 10, and 30 mg/kg/day for 7 days via i.p. infusion) to nude mice harboring established intracranial U87 xenografts produced a significant, dose-dependent prolongation of survival versus control animals. Survival in the control group was 27 +/- 1.7 days, compared with more than 50 days in each of the treatment groups (P < 0.001). At the 30 mg/kg dose level, 100% of animals survived for 120 days without evidence of tumor, a substantial improvement in comparison with lower dose levels (P < 0.01). No overt toxicity was apparent even at the highest Apo2L dose. We conclude that soluble Apo2L/TRAIL is effective in inducing apoptosis in high-grade glioma cells in vitro. Because this ligand appears to exhibit selective cytotoxicity for glioma cells versus non-neoplastic cells in vitro and demonstrates significant activity in vivo when administered systemically in an otherwise uniformly fatal central nervous system glioma model system, Apo2L may constitute a useful therapeutic agent for these challenging tumors.

Basic fibroblast growth factor expression as a predictor of prognosis in pediatric high-grade gliomas.

Clinical and histopathological factors fail to adequately predict outcomes in children with high-grade gliomas, indicating a need to identify relevant biological markers of tumor behavior to guide therapeutic decision-making. Basic fibroblast growth factor (bFGF) is a mitogenic and angiogenic factor that has been observed to be overexpressed in a significant percentage of malignant gliomas, although the prognostic significance of this expression is unknown. To address this issue, the expression status of bFGF was examined immunohistochemically in a series of 27 archival pediatric malignant non-brainstem gliomas treated consecutively at our institution between 1975 and 1992. Tumors were categorized based on expression levels, and the association between expression status and outcome was examined. Sixteen cases showed high levels of expression of bFGF, and 11 showed low levels. There was no correlation between expression status and either tumor histology, patient age, or tumor location. However, there was a significant difference in outcome between patients with high levels of bFGF immunoreactivity and those with low expression. Median progression-free survival was >66 months in the low bFGF group as compared to 6 months in the high bFGF group (P = 0.006). Median overall survival was >66 months in the low bFGF group as compared to 18 months in the high bFGF group (P = 0.03). Tumor bFGF expression seems to be strongly associated with outcome in children with high-grade gliomas and, consequently, may serve as a biological correlate of patient prognosis in conjunction with other prognostic variables.

Epidermal growth factor receptor expression and gene amplification in high-grade non-brainstem gliomas of childhood.

Epidermal growth factor receptor (EGFR) is commonly overexpressed in adult high-grade gliomas. Forty to 50% of such tumors demonstrate amplification of the EGFR gene, often with rearrangement and constitutive activation of the gene product, suggesting that EGFR might play a role in the malignant progression of a subset of these neoplasms. In this regard, several groups have shown that overexpression of EGFR is associated with an adverse outcome in adult gliomas. In contrast to the extensive studies of EGFR status that have been performed in adult high-grade gliomas, little information has been reported about EGFR expression and amplification, as well as their prognostic relevance in high-grade gliomas of childhood, which carry a somewhat more favorable prognosis than their adult counterparts. To address this issue, we examined the expression of EGFR using immunohistochemistry and screened for amplification of the EGFR gene using a competitive PCR in a series of 27 archival pediatric high-grade nonbrainstem gliomas treated consecutively at our institution between 1975 and 1992. Tumors were categorized based on protein expression patterns, and the association between expression status and outcome was examined. Although elevated immunoreactivity for EGFR was observed in 80% of tumors, only two of the cases had gene amplification. No difference in outcome was observed between tumors that exhibited extensive EGFR immunoreactivity and those that did not (P > 0.3). Although EGFR expression did not seem to be of prognostic relevance for the outcome of pediatric patients harboring high-grade nonbrainstem gliomas, the consistently high levels of expression of EGFR in these neoplasms suggest that this receptor plays a role in the malignant phenotype of these tumors. Accordingly, treatment approaches targeting EGFR might be of potential therapeutic benefit for high-grade gliomas of childhood.

A phase I study of high-dose tamoxifen for the treatment of refractory malignant gliomas of childhood.

Recent studies have indicated that the proliferation of malignant gliomas is in part dependent on excessive activation of protein kinase C (PKC)-mediated pathways. Conversely, inhibiting PKC may provide a novel approach for blocking glioma growth. The antiestrogen tamoxifen, a moderately potent PKC inhibitor, has been shown in vitro to block the proliferation of malignant glioma cell lines at concentrations several-fold higher than those typically attained during the treatment of breast cancer; such serum concentrations may be achieved with doses > 40 mg/m2 b.i.d. The safety and efficacy of these high doses for producing disease control in patients with malignant gliomas has recently been noted anecdotally, although a rigorous study of this agent has been lacking. To address this issue, we examined the safety and efficacy of high-dose tamoxifen in a series of children with malignant gliomas that had progressed after conventional therapy. An initial group was treated with 60 mg/m2 p.o. b.i.d. and a second group with 100 mg/m2 b.i.d. Steady-state serum tamoxifen and metabolite levels were measured in most patients. Toxicity with the regimen was minimal; two patients treated at the higher dose required reduction to the lower dose because of asymptomatic prolongation of the QT interval on an electrocardiogram. Although none of the patients exhibited clear-cut tumor regression, 4 of 14 patients had stabilization of previously progressive disease for at least 3 months; the longest survivor lived for 17 months after beginning tamoxifen. The moderate efficacy of this agent in otherwise end-stage disease coupled with its low toxicity and the relative ease of oral administration provides a rationale for proceeding with larger studies of this agent in patients with malignant gliomas, possibly as a means for potentiating the effects of conventional chemotherapeutic agents, which to date have shown limited efficacy in the treatment of these tumors.

Parametric Response Mapping of Apparent Diffusion Coefficient as an Imaging Biomarker to Distinguish Pseudoprogression from True Tumor Progression in Peptide-Based Vaccine Therapy for Pediatric Diffuse Intrinsic Pontine Glioma.

BACKGROUND AND PURPOSE: Immune response to cancer therapy may result in pseudoprogression, which can only be identified retrospectively and may disrupt an effective therapy. This study assesses whether serial parametric response mapping (a voxel-by-voxel method of image analysis also known as functional diffusion mapping) analysis of ADC measurements following peptide-based vaccination may help prospectively distinguish progression from pseudoprogression in pediatric patients with diffuse intrinsic pontine gliomas. MATERIALS AND METHODS: From 2009 to 2012, 21 children, 4-18 years of age, with diffuse intrinsic pontine gliomas were enrolled in a serial peptide-based vaccination protocol following radiation therapy. DWI was acquired before immunotherapy and at 6-week intervals during vaccine treatment. Pseudoprogression was identified retrospectively on the basis of clinical and radiographic findings, excluding DWI. Parametric response mapping was used to analyze 96 scans, comparing ADC measures at multiple time points (from the first vaccine to up to 12 weeks after the vaccine was halted) with prevaccine baseline values. Log-transformed fractional increased ADC, fractional decreased ADC, and parametric response mapping ratio (fractional increased ADC/fractional decreased ADC) were compared between patients with and without pseudoprogression, by using generalized estimating equations with inverse weighting by cluster size. RESULTS: Median survival was 13.1 months from diagnosis (range, 6.4-24.9 months). Four of 21 children (19%) were assessed as experiencing pseudoprogression. Patients with pseudoprogression had higher fitted average log-transformed parametric response mapping ratios (P = .01) and fractional decreased ADCs (P = .0004), compared with patients without pseudoprogression. CONCLUSIONS: Serial parametric response mapping of ADC, performed at multiple time points of therapy, may distinguish pseudoprogression from true progression in patients with diffuse intrinsic pontine gliomas treated with peptide-based vaccination.

The molecular biology of ependymomas.

Intracranial ependymomas are the third most common primary brain tumor in the pediatric population. Although an anaplastic variant is recognized, numerous studies examining the prognostic implications of histological features, such as necrosis, endothelial proliferation and mitoses, have yielded contradictory results. In order to improve outcome prediction in affected patients and to refine therapeutic decision-making, there is a strong need for identifying relevant biological correlates of tumor behavior. The molecular biology of tumors is a rapidly expanding field and includes investigations into cytogenetics, oncogenes, growth factors, growth factor receptors, hormonal receptors, proliferation markers, apoptosis, cell cycle genes and cell adhesion molecules, as well as factors potentially related to therapeutic resistance, such as the multidrug resistance gene. The molecular biology of astrocytic tumors in adults has been the subject of many studies; however, relatively few studies have been focused on ependymomas. Herein we review potential oncological markers in ependymomas that have been identified to date and highlight the limitations of our current knowledge as a basis for defining areas for future investigation.

Neurofibromatosis 1 and 2.

Neurofibromatosis (NF) 1 and 2 are multisystem disorders associated with a variety of neoplastic and non-neoplastic manifestations that typically progress in severity during the lifetime of the affected patient. The importance of appropriately diagnosing these disorders stems from the fact that the natural history of an associated neoplasm, such as a peripheral nerve tumor or an optic glioma, may be significantly different depending on whether or not the lesion arises in a person with NF. In addition, the indications for therapeutic intervention, hierarchy of treatment options and long-term management goals may differ substantially for patients with NF-related versus sporadic tumors. Finally, recognition of the diagnosis comprises an essential step for providing appropriate multidisciplinary evaluation and counseling to affected patients and their families. This article addresses the principal manifestations of these disorders and provides a contemporary review of the diagnostic and therapeutic issues that arise in children with NF1 and NF2.

Characterization and transduction of a retroviral vector encoding human interleukin-4 and herpes simplex virus-thymidine kinase for glioma tumor vaccine therapy.

Vaccination with cytokine-transduced tumor cells represents a potentially important approach to the treatment of central nervous system tumors. We have recently demonstrated the therapeutic efficacy of tumor cell vaccines expressing the murine interleukin 4 (IL-4) and the herpes simplex virus-thymidine kinase in a rat brain tumor model in which nonirradiated vaccine cells can be eliminated by the subsequent administration of ganciclovir. In this report, we demonstrate the construction and characterization of a retroviral vector that encodes human IL-4, neomycin phosphotransferase, and herpes simplex virus-thymidine kinase genes for use in human clinical trials. An MFG-based retroviral vector was used to generate the recombinant retrovirus, TFG-hIL4-Neo-Tk, in which a long terminal repeat-driven polycistronic transcript encodes three cDNAs that are linked and coexpressed using two intervening internal ribosome entry site fragments from the encephalomyocarditis virus. The amphotropic retroviral vector TFG-hIL4-Neo-Tk was then used to infect human primary glioma cultures and skin-derived fibroblasts. After infection and G418 selection, cells produced 89-131 ng/10(6) cells/48 hours of human IL-4, which was determined to be biologically active. Transduced glioma cells were highly sensitive to the cytotoxic effect of ganciclovir. These data demonstrate the suitability of the TFG-hIL4-Neo-Tk vector for therapeutic studies of cytokine-transduced autologous tumor vaccination in patients with malignant gliomas.

The management of brainstem gliomas in patients with neurofibromatosis 1.

The appropriate management of brainstem tumors in patients with neurofibromatosis 1 (NF1) has been problematic because the natural history of these lesions remains poorly defined. To formulate rational guidelines for the evaluation and treatment of these tumors, we reviewed the outcome of 21 patients with brainstem mass lesions followed in our NF clinic during the last 9 years. We subdivided the imaging features of these lesions into four groups: (1) diffuse enlargement of the brainstem with hypointensity on T1-weighted MR images and hyperintensity on T2-weighted images (n = 9); (2) focal enhancing masses (n = 7); (3) intrinsic tectal tumors (n = 5); and (4) focal nonenhancing areas of hypointensity on T1-weighted MR images (n = 2). Two cases exhibited two types of lesions. Twelve patients presented with, or developed, symptoms that were referable to the mass; in nine, the lesion was asymptomatic. A distinguishing feature of these tumors was their generally indolent biological behavior. With a median follow-up of 3.75 years, only 10 patients have had radiographic (n = 9) or clinical (n = 3) evidence of disease progression. In seven of these patients, the tumor subsequently stabilized in size or regressed without intervention. Only four patients, each with a focal enhancing tumor, received specific therapy for the tumor; this consisted of biopsy (n = 1), excision (n = 3), and adjuvant radiotherapy (n = 2). Each of these lesions was a low-grade glioma histologically and each remained stable in size after treatment (median follow-up = 4.25 years). Four patients with tectal tumors underwent insertion of a CSF shunt for hydrocephalus, but required no specific treatment for the tumor. None of the patients with diffuse brainstem lesions or focal areas of hypointensity required any intervention for the tumor. All 21 patients are presently alive and well. We conclude that the biological behavior of brainstem lesions in patients with NF1 differs significantly from that of lesions with a similar appearance in patients without this disorder. Although these lesions may at some time in their course exhibit clinical and radiographic progression, most do not require specific intervention. The lesions that are most likely to progress and require therapy are focal enhancing tumors; however, even lesions in this subgroup may stabilize in size or regress spontaneously without intervention. Based on these results, we recommend that intervention be limited to those lesions that exhibit rapid or unrelenting growth on serial images or that produce significant clinical deterioration.