Inhibition of STAT3 promotes the efficacy of adoptive transfer therapy using type-1 CTLs by modulation of the immunological microenvironment in a murine intracranial glioma

A variety of cancers, including malignant gliomas, show aberrant activation of STAT3, which plays a pivotal role in negative regulation of antitumor immunity. We hypothesized that inhibition of STAT3 signals would improve the efficacy of T cell adoptive transfer therapy by reversal of STAT3-induced immunosuppression in a murine GL261 intracranial glioma model. In vitro treatment of GL261 cells with JSI-124, a STAT3 inhibitor, reversed highly phosphorylated status of STAT3. Systemic i.p. administration of JSI-124 in glioma-bearing immunocompetent mice, but not athymic mice, resulted in prolonged survival, suggesting a role of adaptive immunity in the antitumor effect. Furthermore, JSI-124 promoted maturation of tumor-infiltrating CD11c(+) dendritic cells and activation of tumor-conditioned cytotoxic T cells, enhanced dendritic cells and GL261 production of CXCL-10, a critical chemokine for attraction of Tc1 cells. When i.p. JSI-124 administration was combined with i.v. transfer of Pmel-I mouse-derived type-1 CTLs (Tc1), glioma-bearing mice exhibited prolonged survival compared with i.p. JSI-124 or i.v. Tc1 therapy alone. Flow cytometric analyses of brain infiltrating lymphocytes revealed that JSI-124-treatment enhanced the tumor-homing of i.v. transferred Tc1 cells in a CXCL-10-dependent fashion. Systemic JSI-124 administration also up-regulated serum IL-15 levels, and promoted the persistence of transferred Tc1 in the host. These data suggest that systemic inhibition of STAT3 signaling can reverse the suppressive immunological environment of intracranial tumor bearing mice both systemically and locally, thereby promoting the efficacy of adoptive transfer therapy with Tc1.

Pathologist interobserver variability of histologic features in childhood brain tumors: results from the CCG-945 study

In the Children's Cancer Group-945 trial, study design allowed estimation of overall interpathologist observational agreement for 6 histologic features frequently used in brain tumor diagnoses. We evaluated agreement between pairs of 5 experienced neuropathologists, who had knowledge of the general diagnoses prior to slide readings. We performed this study in an attempt to further improve pathologist interinstitutional agreement. The features mitosis, necrosis, and giant cells had "fair" overall kappa estimates of reproducibility of around 0.5, while endothelial proliferation had only a "poor" overall kappa of 0.35. The Rogot reproducibility index averaged 0.5 for pleomorphism and hyperchromia. The upper bounds for the 10 pair summary agreement estimates were at best 0.65 ("good") for all 6 features. These relatively low-reproducibility estimates for the very small number of histologic features being assessed in tumors institutionally diagnosed as high-grade gliomas indicate that neuropathologists either used different operational definitions or interpreted them differently. We found that we could rank the histologic features from best to worst agreement among study pathologists as necrosis, giant cells, mitosis, endothelial proliferation, hyperchromic nuclei, and pleomorphic cells. We suggest that neuropathologists involved in multi-institutional studies of putative therapies not discard these traditional histologic features, but rather develop standardized operational definitions and measure their variability before beginning the studies. Only after such histologic feature variability studies are conducted will we have the data to identify specific histologic features of value to clinicians and researchers. Agreement and strict adherence to improved nonsubjective diagnostic criteria would improve histologic feature reliability and, consequently, their usefulness in studies.

Metastatic ependymoma: a multi-institutional retrospective analysis of prognostic factors

PURPOSE

Metastatic ependymoma is exceedingly rare at diagnosis with variable prognosis reported in the literature. The purpose of this study was to identify prognostic factors in children with metastatic ependymoma.

PROCEDURE

Data regarding diagnosis, treatment and follow-up for 40 patients from eight institutional cohorts were collected.

RESULTS

Twenty-nine (72%) patients were less than 36 months of age at the time of diagnosis, 28% were females, and 90% of the patients had posterior fossa tumors. Gross total resection (GTR) of the primary tumor was achieved in 16 patients (40%). Adjuvant therapy was variable and included craniospinal irradiation (CSRT), chemotherapy, and chemotherapy with focal irradiation. The 5-year event free survival (EFS) and overall survival (OS) from the time of diagnosis were 29% (+/-7%) and 43% (+/-8%), respectively. Age at diagnosis was associated significantly with both EFS and OS (P < 0.001 for EFS, and P = 0.01 for OS). Patients who were 24-35 months of age at diagnosis had a 5-year EFS of 66% and a 5-year OS of 73%; both survival rates were superior to those of patients younger than 24 months of age or older than 36 months. Patients with GTR achieved a 5-year EFS of 35% and OS of 59%, compared to a 5-year EFS of 25% and OS of 32% for patients who did not achieve GTR (P = 0.12 for EFS, P = 0.03 for OS).

CONCLUSIONS

GTR should be attempted in patients with metastatic ependymoma. A subgroup of patients between 24 and 35 months might have a favorable outcome.

AG490 influences UCN-01-induced cytotoxicity in glioma cells in a p53-dependent fashion, correlating with effects on BAX cleavage and BAD phosphorylation

We determined the cytotoxicity of AG490 as a single agent and in combination with 7-hydroxystaurosporine (UCN-01) in a panel of malignant human glioma cell lines. Because p53 has important roles in cell cycle checkpoints, it has been anticipated that modulation of checkpoint pathways should sensitize p53 defective cells while sparing the normal cells. Cell proliferation was determined from dose-response curves. AG490 was effective as a cytotoxic agent alone regardless of p53 status. Combining the Chk1 inhibitor UCN-01 dramatically enhanced the response to AG490 in p53-mutated or deleted glioma cells. An opposite effect was noted in p53-wild type cells, in which UCN-01 and AG490 had antagonistic effects on cell proliferation and viability. We found that AG490 enhanced BAD phosphorylation in p53 wild type glioma cells, which appeared to protect against UCN-01-induced cytotoxicity, whereas AG490 enhanced UCN-01-induced cytotoxicity in p53 defective cell lines by suppression of BAD phosphorylation and induction of BAX and PARP cleavage. These observations highlight the potential for genotype-dependent factors to strongly influence response to signaling-targeted therapies in malignant gliomas and the importance of considering such factors in correlative response analyses for these agents.

Autologous glioma cell vaccine admixed with interleukin-4 gene transfected fibroblasts in the treatment of patients with malignant gliomas

Background

The prognosis for malignant gliomas remains dismal. We addressed the safety, feasibility and preliminary clinical activity of the vaccinations using autologous glioma cells and interleukin (IL)-4 gene transfected fibroblasts.

Methods

In University of Pittsburgh Cancer Institute (UPCI) protocol 95-033, adult participants with recurrent glioblastoma multiforme (GBM) or anaplastic astrocytoma (AA) received gross total resection (GTR) of the recurrent tumors, followed by two vaccinations with autologous fibroblasts retrovirally transfected with TFG-IL4-Neo-TK vector admixed with irradiated autologous glioma cells. In UPCI 99-111, adult participants with newly diagnosed GBM or AA, following GTR and radiation therapy, received two intradermal vaccinations with the TFG-IL4-Neo-TK-transfected fibroblasts admixed with type-1 dendritic cells (DC) loaded with autologous tumor lysate. The participants were evaluated for occurrence of adverse events, immune response, and clinical response by radiological imaging.

Results and Discussion

In UPCI 95-033, only 2 of 6 participants received the vaccinations. Four other participants were withdrawn from the trial because of tumor progression prior to production of the cellular vaccine. However, both participants who received two vaccinations demonstrated encouraging immunological and clinical responses. Biopsies from the local vaccine sites from one participant displayed IL-4 dose-dependent infiltration of CD4⁺ as well as CD8⁺ T cells. Interferon (IFN)-γ Enzyme-Linked Immuno-SPOT (ELISPOT) assay in another human leukocyte antigen (HLA)-A2⁺ participant demonstrated systemic T-cell responses against an HLA-A2-restricted glioma-associated antigen (GAA) epitope EphA2_883–891. Moreover, both participants demonstrated clinical and radiological improvement with no evidence of allergic encephalitis, although both participants eventually succumbed with the tumor recurrence. In 99-111, 5 of 6 enrolled participants received scheduled vaccinations with no incidence of major adverse events. Monocyte-derived DCs produced high levels of IL-12 p70. Treatment was well tolerated; however, we were unable to observe detectable IFN-γ post-vaccine responses or prolonged progression-free survival in these participants.

Conclusion

Feasibility challenges inherent in the generation of a patient-specific gene transfection-based vaccine strongly suggests the need for more practical formulations that would allow for the timely administration of vaccines. Nevertheless, successful generation of type-1 DCs and preliminary safety in the current study provide a strong rationale for further efforts to develop novel glioma vaccines.

Molecular analysis of pediatric brain tumors

The identification of molecular genetic abnormalities in specific types of pediatric brain tumors is beginning to play a role in the stratification of patients into treatment groups. The finding of an INI1 alteration in an atypical teratoid/rhabdoid tumor or malignant neoplasm with overlapping histologic features will be required for entry onto disease-specific protocols within the Children's Oncology Group. Refinement in the classification of medulloblastoma and malignant glioma patients will likely depend on the genetic and signaling pathways that characterize these tumors. Advances in this area will depend on the ability to identify new disease genes, validate prognostic markers, and develop biologically based therapeutic strategies to tailor treatment.

Phase I and pharmacokinetic study of the oral farnesyltransferase inhibitor lonafarnib administered twice daily to pediatric patients with advanced central nervous system tumors using a modified continuous reassessment method: a Pediatric Brain Tumor Consortium Study

PURPOSE

A dose-escalation phase I and pharmacokinetic study of the farnesyltransferase inhibitor lonafarnib (SCH66336) was conducted in children with recurrent or progressive CNS tumors. Primary objectives were to estimate the maximum-tolerated dose (MTD) and to describe the dose-limiting toxicities (DLTs) and pharmacokinetics of lonafarnib. Farnesylation inhibition of HDJ-2 in peripheral blood was also measured.

PATIENTS AND METHODS

Lonafarnib was administered orally twice daily at dose levels of 70, 90, 115, 150, and 200 mg/m2/dose bid. A modified continual reassessment method (CRM) was used to estimate the MTD based on actual dosages of lonafarnib administered and toxicities observed during the initial 4 weeks of treatment.

RESULTS

Fifty-three children with progressive or recurrent brain tumors were enrolled, with a median age of 12.2 years (range, 3.9 to 19.5 years). Dose-limiting pneumonitis or myelosuppression was observed in three of three patients at the 200 mg/m2/dose level. A relatively constant DLT rate at the 70, 90, and 115 mg/m2/dose levels resulted in a recommended phase II dose of 115 mg/m2/dose. Significant diarrhea did not occur with prophylactic loperamide. Both radiographic response (one anaplastic astrocytoma) and stable disease (one medulloblastoma, two high-grade and four low-grade gliomas, one ependymoma, and one sarcoma) were noted, and seven patients remained on treatment for 1 year or longer.

CONCLUSION

Although the estimated MTD by the CRM model was 98.5 mg/m2/dose, because of the relatively constant observed DLT rate at the lower four dose levels, the recommended phase II dose of lonafarnib is 115 mg/m2/dose administered twice daily by mouth with concurrent loperamide.

Fully endoscopic expanded endonasal approach treating skull base lesions in pediatric patients

OBJECT

The authors reviewed their experience with endoscopic approaches to determine their safety and efficacy in the treatment of pediatric patients who harbor skull base lesions. Although they were interested in ascertaining outcomes after surgery as well as validating and defining indications and limitations of these approaches, the authors recognized that the follow-up duration was inadequate to assess long-term outcomes.

METHODS

The authors conducted a retrospective review of all endoscopic procedures performed at their institution between January 2000 and September 2005. The procedures were categorized into a series of anatomical modular approaches. Twenty-five patients 18 years of age or younger were identified. The surgical goals were individualized and included gross-total resection, partial resection, biopsy, decompression of neural structures, and repair of a cerebrospinal fluid (CSF) leak. One patient required an open procedure in addition to the expanded endonasal approach for definitive therapy. No patient suffered a neurological deficit, vascular injury, or central nervous system infection. A CSF leak was the most common complication and occurred in two (8%) of the 25 patients.

CONCLUSIONS

In well-selected patients, the expanded endonasal approach represents a safe, effective, and minimally invasive technique for the treatment of skull base lesions in children. Incremental experience is needed for acquiring the skills with endoscopic techniques to progress to the more complex modular approaches.

Tumor cells from ultrasonic aspirations of glioblastomas migrate and form spheres with radial outgrowth

Studies of primary cells from malignant brain tumors such as glioblastomas are limited by the small size of surgically resected specimens. However, glioblastomas are also frequently debulked via ultrasonic aspiration. In this study, we examined the functional competence and growth of their aspirated cells. Cells from minced tissue and aspirations were comparable in migration, formation of pseudopodia, development of cellular spheres with radial outgrowth, and neuroectodermal features. Cultures were maintained for more than six weeks without fibroblastic overgrowth. Our observations show that ultrasonically aspirated specimens contain cells useful for studies of tumor migration and growth of tumorspheres.

Corridor surgery: the current paradigm for skull base surgery

INTRODUCTION

Clival chordomas are rare tumors, especially in the pediatric population. In this report, we present the case of a 3-year-old boy who was found to have a large posterior pharyngeal, clival, and posterior fossa tumor detected on a CT scan after a closed head injury.

DISCUSSION

Further questioning revealed a history of ataxia and dysphagia. Imaging confirmed severe extrinsic brain stem compression. The tumor was resected in multiple stages utilizing a minimally invasive endoscopic endonasal technique along with open transfacetal, transcondylar approach through the carotid-vertebral window. The child suffered no permanent complications as a result of our treatment and his dysphagia significantly improved. Although a complete resection was not feasible due to vascular encasement by the tumor, extensive decompression was obtained with minimal morbidity.

CONCLUSION

We present this case to illustrate a new paradigm of skull base surgical approaches for large clival lesions in pediatric patients that allows aggressive resection with minimal morbidity.

Phase I trial of imatinib in children with newly diagnosed brainstem and recurrent malignant gliomas: a Pediatric Brain Tumor Consortium report

This study estimated the maximum tolerated dose (MTD) of imatinib with irradiation in children with newly diagnosed brainstem gliomas, and those with recurrent malignant intracranial gliomas, stratified according to use of enzyme-inducing anticonvulsant drugs (EIACDs). In the brainstem glioma stratum, imatinib was initially administered twice daily during irradiation, but because of possible association with intratumoral hemorrhage (ITH) was subsequently started two weeks after irradiation. The protocol was also amended to exclude children with prior hemorrhage. Twenty-four evaluable patients received therapy before the amendment, and three of six with a brainstem tumor experienced dose-limiting toxicity (DLT): one had asymptomatic ITH, one had grade 4 neutropenia and, one had renal insufficiency. None of 18 patients with recurrent glioma experienced DLT. After protocol amendment, 3 of 16 patients with brainstem glioma and 2 of 11 patients with recurrent glioma who were not receiving EIACDs experienced ITH DLTs, with three patients being symptomatic. In addition to the six patients with hemorrhages during the DLT monitoring period, 10 experienced ITH (eight patients were symptomatic) thereafter. The recommended phase II dose for brainstem gliomas was 265 mg/m(2). Three of 27 patients with brainstem gliomas with imaging before and after irradiation, prior to receiving imatinib, had new hemorrhage, excluding their receiving imatinib. The MTD for recurrent high-grade gliomas without EIACDs was 465 mg/m(2), but the MTD was not established with EIACDs, with no DLTs at 800 mg/m(2). In summary, recommended phase II imatinib doses were determined for children with newly diagnosed brainstem glioma and recurrent high-grade glioma who were not receiving EIACDs. Imatinib may increase the risk of ITH, although the incidence of spontaneous hemorrhages in brainstem glioma is sufficiently high that this should be considered in studies of agents in which hemorrhage is a concern.

Rarity of PTEN deletions and EGFR amplification in malignant gliomas of childhood: results from the Children's Cancer Group 945 cohort

OBJECT

In reporting on molecular studies involving malignant gliomas in adults, authors have noted that deletions of PTEN and amplification of EGFR are common and may contribute to tumor development, providing a rationale for a number of therapies aimed at these molecular targets. The frequency of comparable abnormalities has not been defined in a sizable pediatric cohort. To address this issue, we examined tumor samples from the Children's Cancer Group 945 study, a large randomized trial of treatment for childhood malignant gliomas.

METHODS

Tissue sections in 62 evaluable cases were examined, and the tumors were isolated by microdissection. Polymerase chain reaction amplification was used to detect PTEN mutations. Deletions of PTEN were also assessed by fluorescence in situ hybridization (FISH) in 27 cases and loss of heterozygosity analysis in 54; EGFR was assessed using immunohistochemistry to identify areas with maximal EGFR expression, followed by FISH to determine EGFR amplification. Alteration of the PTEN sequence was detected in just one of 62 tumors, in conjunction with loss of chromosome 10; PTEN deletions without mutation were evident in seven additional tumors. The PTEN alterations were more common in glioblastoma multiforme (seven of 25 tumors) than other tumor subgroups (one of 37 tumors) (p = 0.0056). Although 14 of 38 evaluable tumors had increased EGFR expression compared to normal tissue, only one tumor exhibited amplification of EGFR.

CONCLUSIONS

Alterations in PTEN and amplification of EGFR are uncommon in pediatric malignant gliomas, in contrast to adult malignant gliomas. From this one can infer that the pediatric and adult tumors involve distinct molecular causes. The results of this study have important implications for the adaptation of glioma therapies aimed at molecular targets in adults to the treatment of childhood gliomas, and highlight the need for investigations of therapies specifically directed toward childhood tumors.

Anaplastic mixed gliomas and anaplastic oligodendroglioma in children: results from the CCG 945 experience

PURPOSE

To review interpathologist diagnosis variability and survival of children treated for either anaplastic mixed glioma (AMG) or anaplastic oligodendroglioma (AO) with surgery, irradiation and chemotherapy.

PATIENTS AND METHODS

Two hundred and fifty patients with an institutional diagnosis of malignant glioma were enrolled on Children's Cancer Group CCG-945 between 1985 and 1991, and administered vincristine during involved field radiotherapy, then six cycles of prednisone, lomustine and, vincristine; or two cycles of "eight-drugs-in-one-day" (8-in-1) chemotherapy then involved-field radiotherapy followed by six cycles of 8-in-1 chemotherapy. Central review of institutional pathology was post hoc by five experienced neuropathologists.

RESULTS

Twenty-six children had institutional diagnoses of AMG and four had AO. Complete resection and cerebral tumor location was associated with better overall survival (OS) in patients with institutional diagnoses of AMG. However, central review established that only nine of 26 children had AMG: either mixed oligoastrocytoma (MOA) or anaplastic mixed oligoastrocytoma (AOA) and only one had AO. Central review revealed five more patients with AMG, but none with AO. Institutional and CCG central review diagnoses of AMG or AO had poor Jaccard reliabilities of 0.29 and 0.25 respectively. Five-year EFS and OS for five children with centrally confirmed MOA was 50 +/- 20%, with four centrally confirmed AOA was 37.5 +/- 17%. After central review, small samples made tests for differences in survival between regimes impossible.

CONCLUSION

Diagnosis of these tumors is challenging, with only 35% of institutional diagnoses confirmed for AMG and 25% for AO, and survival among children with these tumors is poor, despite intensive therapy. This suggests reliable diagnostic markers and new therapeutic approaches are needed.

Progression-associated genes in astrocytoma identified by novel microarray gene expression data reanalysis

Astrocytoma is graded as pilocytic (WHO grade I), diffuse (WHO grade II), anaplastic (WHO grade III), and glioblastoma multiforme (WHO grade IV). The progression from low- to high-grade astrocytoma is associated with distinct molecular changes that vary with patient age, yet the prognosis of high-grade tumors in children and adults is equally dismal. Whether specific gene expression changes are consistently associated with all high-grade astrocytomas, independent of patient age, is not known. To address this question, we reanalyzed the microarray datasets comprising astrocytomas from children and adults, respectively. We identified nine genes consistently dysregulated in high-grade tumors, using four novel tests for identifying differentially expressed genes. Four genes encoding ribosomal proteins (RPS2, RPS8, RPS18, RPL37A) were upregulated, and five genes (APOD, SORL1, SPOCK2, PRSS11, ID3) were downregulated in high-grade by all tests. Expression results were validated using a third astrocytoma dataset. APOD, the most differentially expressed gene, has been shown to inhibit tumor cell and vascular smooth muscle cell proliferation. This suggests that dysregulation of APOD may be critical for malignant astrocytoma formation, and thus a possible novel universal target for therapeutic intervention. Further investigation is needed to evaluate the role of APOD, as well as the other genes identified, in malignant astrocytoma development.

Albumin marks pseudopodia of astrocytoma cells responding to hepatocyte growth factor or serum

It is well accepted that dysfunction in the blood brain barrier (BBB) allows permeation of albumin from the bloodstream into astrocytic brain tumors, especially glioblastomas, the most aggressive astrocytomas. In vitro, bovine serum albumin (BSA) aids functional cell assays by maintaining cytokines and growth factors in solution and delivering its cargo of fatty acids. Earlier, we showed that BSA was prominent in lysates prepared from pseudopodia formed by U87 astrocytoma cells. The present studies investigated the association of albumin with pseudopodia formed by U87 and LN229 astrocytoma cells. With hepatocyte growth factor (HGF) stimulation, cell migration was enhanced and BSA, especially its dimerized form, was prominent in pseudopodia compared to unmigrated cells on one-dimensional gels and immunoblots. When lysates were equalized for levels of glyceraldehyde-3-phosphate dehydrogenase, the rise for BSA levels in pseudopodia vs migrated cells was comparable or greater than levels noted for established pseudopodial proteins, beta-actin and ezrin. The increase for dimerized BSA in pseudopodia compared to unmigrated cells was greater than the rise in levels of beta-actin, ezrin, HGF, and phosphorylated Met when pseudopodia were harvested from filters with 1 mum pores using either cell line. Fluorescein (F)-labeled BSA co-localized with HGF on actin-rich cellular protrusions and with CM-DiI labeled pseudopodial plasma membranes. The F-BSA highlighted small, individual pseudopodial profiles more so than complex pseudopodial networks (reticulopodia) or unmigrated cells. Labeled human serum albumin also decorated pseudopodia preferentially. Albumin's association with pseudopodia may help to explain its selective accumulation in astrocytomas in vivo. The leaky BBB permits serum albumin to enter the microenvironment of astrocytomas thus allowing their invasive cells contact with serum albumin as a source of fatty acids that would be useful for remodeling cell membranes in pseudopodia. Thus, albumin potentially aids and marks invasion as it accumulates in these tumors.

Coadministration of Sorafenib with Rottlerin Potently Inhibits Cell Proliferation and Migration in Human Malignant Glioma Cells

Mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) are activated in the majority of gliomas and contribute to tumor cell growth and survival. Sorafenib (Bay43-9006; Nexavar) is a dual-action Raf and vascular endothelial growth factor receptor inhibitor that blocks receptor phosphorylation and MAPK-mediated signaling and inhibits growth in a number of tumor types. Because our initial studies of this agent in a series of glioma cell lines showed only partial growth inhibition at clinically achievable concentrations, we questioned whether inhibition of PKC signaling using the PKC-delta inhibitor rottlerin might potentiate therapeutic efficacy. Proliferation assays, apoptosis induction studies, and Western immunoblot analysis were conducted in cells treated with sorafenib and rottlerin as single agents or in combination. Sorafenib and rottlerin reduced proliferation in all cell lines when used as single agents, and the combination produced marked potentiation of growth inhibition. Flow-cytometric measurements of cells stained with Annexin V-propidium iodide and immunocytochemical assessment of cytochrome c and apoptosis-inducing factor release demonstrated that addition of rottlerin resulted in significantly higher levels of apoptosis than sorafenib alone. In addition, the combination of sorafenib and rottlerin reduced or completely inhibited the phosphorylation of extracellular signal-regulated kinase and Akt and down-regulated cell cycle regulatory proteins such as cyclin-D1, cyclin-D3, cyclin-dependent kinase (cdk)4, and cdk6 in a dose- and time-dependent manner. Our results clearly indicate that inhibition of PKC-delta signaling enhances the antiproliferative effect of sorafenib in malignant human glioma cell lines and support the examination of combinations of signaling inhibitors in these tumors.

O6-methylguanine-DNA methyltransferase expression strongly correlates with outcome in childhood malignant gliomas: results from the CCG-945 Cohort

PURPOSE

O6-methylguanine-DNA methyltransferase (MGMT) functions to counteract the cytotoxic effects of alkylating agents, such as nitrosoureas, which play a central role in the treatment of childhood malignant gliomas. Epigenetic silencing of MGMT has been associated with prolonged survival in adults with malignant gliomas, although the association between MGMT expression status and outcome in pediatric malignant gliomas has not been defined.

METHODS

We examined the association between MGMT expression and survival duration using tumor samples from the Children's Cancer Group 945 study, the largest randomized trial for childhood malignant gliomas completed to date. All patients received alkylator-based chemotherapy as a component of adjuvant therapy. Archival histopathologic material yielded tissue of sufficient quality for immunohistochemical assessment of MGMT expression status in 109 specimens.

RESULTS

Twelve of the 109 samples demonstrated overexpression of MGMT compared with normal brain. Five-year progression-free survival was 42.1% +/- 5% in the 97 patients whose tumors had low levels of MGMT expression versus 8.3% +/- 8% in the 12 patients whose tumors overexpressed MGMT (P = .017, exact log-rank test). The association between MGMT overexpression and adverse outcome remained significant after stratifying for institutional histologic diagnosis (eg, anaplastic astrocytoma or glioblastoma multiforme), as well as age, amount of residual tumor, and tumor location.

CONCLUSION

Overexpression of MGMT in childhood malignant gliomas is strongly associated with an adverse outcome in children treated with alkylator-based chemotherapy, independently of a variety of clinical prognostic factors.

Late rapid deterioration after endoscopic third ventriculostomy: additional cases and review of the literature

OBJECT

Late rapid deterioration after endoscopic third ventriculostomy (ETV) is a rare complication. The authors previously reported three deaths from three centers. Three other deaths and a patient who experienced rapid deterioration have also been reported. Following the death at the University of Toronto of an additional patient who underwent surgery elsewhere, they canvassed pediatric neurosurgeons in North America, Europe, Australia, and Asia for additional cases.

METHODS

An email was sent to the members of the Canadian Congress of Neurological Sciences who are pediatric neurosurgeons, to the pediatric neurosurgery email list of the American Association of Neurological Surgeons, to the email list of the International Society for Pediatric Neurosurgery, and to designated neurosurgeons in the United Kingdom, France, Japan, Korea, Taiwan, and Australia, who in turn contacted pediatric neurosurgeons in their countries. A data form was provided, and data from previously reported cases were extracted. Nine additional cases were identified, and the results were collated with those of the seven cases previously reported. Patient age at surgery ranged from 2 days to 13 years (mean 7.6 years). The most common causes of hydrocephalus were aqueductal stenosis in 50% of patients and tectal glioma in 25% of patients. The time to treatment failure ranged from 5 weeks to 7.8 years (mean 2.5 years). Thirteen patients died, one patient was in a vegetative state, one patient was mildly disabled, and one patient whose condition deteriorated outside the operating room was alive and well. In the 13 patients in whom the ventriculostomy site was visualized at autopsy or repeated endoscopy, the ventriculostomy was shown to be occluded.

CONCLUSIONS

Late rapid deterioration is a rare but lethal complication of ETV. The mechanism is unclear, but deterioration can occur long after the ETV becomes occluded. Patients and caregivers should be counseled regarding this potential complication. An indwelling ventricular access device is an option for patients undergoing ETV.

Parental heat exposure and risk of childhood brain tumor: a Children's Oncology Group study

Medulloblastoma (MB) and primitive neuroectodermal tumor (PNET) are histologically similar brain tumors that occur mostly in children. As part of a comprehensive case-control study of MB/PNET, this study explored parental exposure to heat and electromagnetic fields as potential risk factors. Parents of 318 cases (<6 years of age at diagnosis in 1991-1997 and registered with the Children's Cancer Group) and 318 controls selected by random digit dialing were interviewed. In univariate analyses, moderately strong associations were observed for mother's sauna use close to conception (odds ratio = 3.8, 95% confidence interval (CI): 1.0, 13.7) or in the first trimester (odds ratio = 3.6, 95% CI: 0.7, 17.3) and for father's exposure in the 3 months before the pregnancy to sauna (odds ratio = 2.4, 95% CI: 1.3, 4.5), electric blanket (odds ratio = 2.0, 95% CI: 0.9, 4.3), or any heat source (for higher exposure: odds ratio = 2.5, 95% CI: 1.4, 4.6). In multivariate models, father's sauna use and father's exposure to any heat source were associated with MB/PNET in a dose-response fashion (for high exposure: odds ratio = 3.4, 95% CI: 1.2, 9.7, and odds ratio = 2.1, 95% CI: 1.1, 4.3, respectively). This new observation regarding paternal exposure to heat just prior to the index pregnancy deserves consideration in future animal and human studies of MB/PNET.

Identification of interleukin-13 receptor alpha2 peptide analogues capable of inducing improved antiglioma CTL responses

Restricted and high-level expression of interleukin-13 receptor alpha2 (IL-13Ralpha2) in a majority of human malignant gliomas makes this protein an attractive vaccine target. We have previously described the identification of the IL-13Ralpha2(345-353) peptide as a human leukocyte antigen-A2 (HLA-A2)-restricted CTL epitope. However, as it remains unclear how efficiently peptide-based vaccines can induce specific CTLs in patients with malignant gliomas, we have examined whether analogue epitopes could elicit heteroclitic antitumor T-cell responses versus wild-type peptides. We have created three IL-13Ralpha2 analogue peptides by substitutions of the COOH-terminal isoleucine (I) for valine (V) and the NH(2)-terminal tryptophan (W) for either alanine (A), glutamic acid (E), or nonsubstituted (W; designated as 1A9V, 1E9V, and 9V, respectively). In comparison with the native IL-13Ralpha2 epitope, the analogue peptides 9V and 1A9V displayed higher levels of binding affinity and stability in HLA-A2 complexes and yielded an improved stimulatory index for patient-derived, specific CTLs against the native epitope expressed by HLA-A2(+) glioma cells. In HLA-A2-transgenic HHD mice, immunization with the peptides 9V and 1A9V induced enhanced levels of CTL reactivity and protective immunity against an intracranial challenge with IL13Ralpha2-expressing syngeneic tumors when compared with vaccines containing the native IL-13Ralpha2 epitope. These findings indicate highly immunogenic IL-13Ralpha2 peptide analogues may be useful for the development of vaccines capable of effectively expanding IL-13Ralpha2-specific, tumor-reactive CTLs in glioma patients.

Cooperative inhibitory effect of ZD1839 (Iressa) in combination with 17-AAG on glioma cell growth

ZD1839 ("Iressa") is an orally active, selective epidermal growth factor (EGF) receptor-tyrosine kinase inhibitor. We evaluated the antitumor activity of ZD1839 in combination with HSP90 antagonist, 17-AAG in malignant human glioma cell lines. ZD1839 independently produced a dose-dependent inhibition of cellular proliferation in glioma cells grown in culture with time- and dose-dependent accumulation of cells in G(1) phase of the cell cycle on flow cytometric analysis, although the concentrations required for optimal efficacy were at or above the limits of clinically achievable levels. Because the heat shock protein (HSP) is involved in the conformational maturation of a number of signaling proteins critical to the proliferation of malignant glioma cells, we hypothesized that the HSP90 inhibitor 17-AAG would potentiate ZD 1839-mediated glioma cytotoxicity by decreasing the activation status of EGF receptor, as well as down regulating the levels of other relevant signaling effectors. We, therefore, examined the effects of ZD1839 and 17-AAG, alone and in combination, on signal transduction and apoptosis in a series of malignant glioma cell lines. Simultaneous exposure to these inhibitors significantly induced cell death and quantitative analysis revealed that interaction between ZD1839 and 17-AAG-induced cytotoxicity was synergistic, leading to a pronounced increase in active caspase-3 and PARP cleavage. No significant growth inhibition or caspase activation was seen in control cells. The enhanced cytotoxicity of this combination was associated with diminished Akt activation and a significant downregulation of EGFR receptor, Raf-1 and mitogen activated protein kinase (MAPK). Cells exposed to 17-AAG and ZD1839 displayed a significant reduction in cell cycle regulatory proteins, such as CDK4 and CDK6. Taken together, these findings suggest that ZD1839, an EGF receptor tyrosine kinase inhibitor, plays a critical role in regulating the apoptotic response to 17-AAG and that multi-site targeting of growth signaling and cell survival pathways could provide a potent strategy to treat patients with malignant gliomas.

Effect of trichostatin A, a histone deacetylase inhibitor, on glioma proliferation in vitro by inducing cell cycle arrest and apoptosis

OBJECT

Trichostatin A (TSA) is a histone deacetylase inhibitor that causes growth inhibition of malignant cells. The authors' goal was to evaluate its effect on cell growth and cell cycle regulation in a large panel of glioma cell lines, as well as in human astrocytes, fibroblasts, and endothelial cells.

METHODS

Cell growth in response to TSA was evaluated using a tetrazolium colorimetric assay and a clonogenic assay. Cell cycle effects were examined using flow cytometry. A DNA fragmentation assay was used to evaluate induction of apoptosis. Histone acetylation status and the expression of p21WAF1, phosphorylated retinoblastoma protein (Rb), poly(adenosine diphosphate-ribose) polymerase (PARP), and caspase-3 were studied using Western blot analysis. In the glioma cell lines, there was significant inhibition of cell growth and detection of increased levels of acetylated histones after TSA treatment. The mechanisms underlying the growth inhibition include cell cycle arrest at the G2/M phase and apoptosis induction. The expression of p21WAF1 was activated, with a temporally related decrease in levels of phosphorylated Rb. Apoptosis was preceded by detection of cleaved PARP and activated caspase-3. The effects of TSA were less pronounced or absent in human astrocytes, fibroblasts, and endothelial cells.

CONCLUSIONS

The TSA caused inhibition of glioma cell growth by both cell cycle arrest and apoptosis. Cell cycle arrest was associated with an increase in p21WAF1 expression and a decrease in phosphorylated Rb. Apoptosis was mediated at least partly through the activation of caspase-3. Because of the differential effects in glioma cells compared with nonneoplastic cells, TSA may provide a novel strategy for achieving tumor growth inhibition and cytotoxicity. Further investigation is warranted.