Long-term survival of children less than six years of age enrolled on the CCG-945 phase III trial for newly-diagnosed high-grade glioma: a report from the Children's Oncology Group.

BACKGROUND: We analyzed the long-term survival of children under 6 years of age (<6 years) enrolled upon the Children's Cancer Group (CCG)-945 high-grade glioma (HGG) study to determine the impact of intrinsic biological characteristics as well as treatment upon both survival and quality of life (QOL) in this younger age population. PROCEDURE: Analyses were undertaken on patients <6 years with institutionally diagnosed HGG enrolled on the CCG-945 trial. Comparisons of survival were performed for patients <3 years of age (<3 years) (treated with intent to avoid irradiation) versus those between 3 and 6 years of age (3-6 years) (treated with irradiation and chemotherapy) at diagnosis. Discordance between the institutional diagnoses of HGG and consensus-reviewed diagnoses led us to perform further survival analyses for both groups. We compared the two groups of patients for biological markers, and evaluated the neuropsychological and QOL outcomes of long-term survivors. RESULTS: Patients <3 years (n = 49, 19.5% of all enrolled patients) at diagnosis had a 10-year EFS and OS of 29 ± 6.5% and 37.5 ± 7%, respectively, while for patients 3-6 years (n = 34, 13.5% of all enrolled patients) 10-year EFS and OS were 35 ± 8% and 36 ± 8%, respectively. Molecular marker analysis showed that a smaller proportion of patients <3 years harbored TP53 mutations (P = 0.05). Analysis of QOL outcomes with a median length of follow-up of 15.1 years (9.5-19.2) showed comparable results. CONCLUSIONS: QOL and survival data were similar for the two groups. A larger prospective study is justified to study the efficacy of chemotherapy only regimens in younger children.

Primary neurosurgery for pediatric low-grade gliomas: a prospective multi-institutional study from the Children's Oncology Group.

BACKGROUND: Central nervous system neoplasms are the most common solid tumors in children, and more than 40% are low-grade gliomas. Variable locations, extent of resection, postoperative neurodiagnostic evaluation, and histology have confounded therapy and outcome. OBJECTIVES: To investigate disease control and survival after surgery. METHODS: A prospective natural history trial from 1991 to 1996 produced a subset of patients with low-grade gliomas managed by primary surgery and subsequent observation. Patients were evaluable if eligibility, tumor location, and extent of resection were confirmed by pathological diagnosis, preoperative and postoperative imaging, and the surgeon's report. Primary end points were overall survival (OS), progression-free survival (PFS), and postprogression survival. RESULTS: Of 726 patients enrolled, 518 were fully evaluable for analysis. The 5- and 8-year OS rates were 97% ± 0.8% and 96% ± 0.9%, respectively, and PFS rates were 80% ± 1.8% and 78% ± 2.0%. In univariate analyses, histological type, extent of residual tumor, and disease site were significantly associated with PFS and OS. In multivariate analysis, gross total resection (GTR) without residual disease was the predominant predictor of PFS. In patients with limited residual disease, 56% were free of progression at 5 years. CONCLUSION: GTR should be the goal when it can be achieved with an acceptable functional outcome. The variable rate of progression after incomplete resection highlights the need for new predictors of tumor behavior.

Mismatch repair deficiency is an uncommon mechanism of alkylator resistance in pediatric malignant gliomas: a report from the Children's Oncology Group.

BACKGROUND: Alkylating agents are commonly used in the treatment of childhood malignant gliomas. Overexpression of O(6)-methylguanine-DNA methyltransferase (MGMT) constitutes an important mechanism for resistance to such agents, and MGMT status has been associated with outcome in several recent trials. Deficiency in mismatch repair (MMR) function has been implicated in preclinical studies as an additional potential mechanism of resistance to methylating agents, such as temozolomide, independent of tumor MGMT status. However, the frequency of this abnormality as a clinical resistance mechanism in childhood malignant gliomas has not been well characterized. METHODS: To address this issue, we examined the frequency of microsatellite instability (MSI), a marker of defective MMR, in a series of 68 tumors, derived from newly diagnosed patients treated on the Children's Cancer Group 945 study, and the Children's Oncology Group ACNS0126 and 0423 studies. MSI was assessed using a panel of six microsatellite markers, including BAT-25, BAT-26, CAT-25, D2S123, D5S346, and D17S250. MGMT immunoreactivity was assessed in parallel to allow comparison of the relative incidence of MGMT overexpression and MSI. RESULTS: Only three tumors had high-level MSI involving three or more markers; the remainder had no MSI at any of the loci examined. These children did not have unusual features in terms of their outcome. In contrast to the infrequency of MSI, 25 tumors (37%) exhibited MGMT overexpression as assessed by immunohistochemistry. None of the tumors with MSI exhibited overexpression of MGMT. CONCLUSION: MMR deficiency is an infrequent contributor to initial alkylator resistance in children with malignant gliomas.

Tissue specific DNA methylation of CpG islands in normal human adult somatic tissues distinguishes neural from non-neural tissues.

Although most CpG islands are generally thought to remain unmethylated in all adult somatic tissues, recent genome-wide approaches have found that some CpG islands have distinct methylation patterns in various tissues, with most differences being seen between germ cells and somatic tissues. Few studies have addressed this among human somatic tissues and fewer still have studied the same sets of tissues from multiple individuals. In the current study, we used Restriction Landmark Genomic Scanning to study tissue specific methylation patterns in a set of twelve human tissues collected from multiple individuals. We identified 34 differentially methylated CpG islands among these tissues, many of which showed consistent patterns in multiple individuals. Of particular interest were striking differences in CpG island methylation, not only among brain regions, but also between white and grey matter of the same region. These findings were confirmed for selected loci by quantitative bisulfite sequencing. Cluster analysis of the RLGS data indicated that several tissues clustered together, but the strongest clustering was in brain. Tissues from different brain regions clustered together, and, as a group, brain tissues were distinct from either mesoderm or endoderm derived tissues which demonstrated limited clustering. These data demonstrate consistent tissue specific methylation for certain CpG islands, with clear differences between white and grey matter of the brain. Furthermore, there was an overall pattern of tissue specifically methylated CpG islands that distinguished neural tissues from non-neural.

Myeloablative chemotherapy with autologous bone marrow rescue in children and adolescents with recurrent malignant astrocytoma: outcome compared with conventional chemotherapy: a report from the Children's Oncology Group.

PURPOSE: Children and adolescents with malignant astrocytomas recurring after initial treatment have a dismal prognosis, with only rare patients surviving 1-year beyond recurrence. The purpose of this study was to attempt to improve their survival. METHODS: Twenty-seven children and adolescents with malignant astrocytomas [17 glioblastoma multiforme and 10 anaplastic astrocytoma (AA)] following initial tumor progression, received myeloablative chemotherapy followed by autologous marrow rescue with one of three thiotepa and etoposide-based chemotherapy regimens, administered alone (n = 11) or combined with carmustine (n = 5) or carboplatin (n = 11). Time to progression and death following myeloablative chemotherapy for these patients was compared non-randomly with outcome of a contemporaneously treated cohort of similar patients who received only conventional chemotherapy following initial tumor progression. The two cohorts were compared for age, histology, prior therapies, extent of surgical resection at progression, and time from initial diagnosis to progression. RESULTS: Five of 27 children (two with glioblastoma multiforme and three with AA) survive event-free from 8.3 to 13.3 years (median of 11.1 years) following myeloablative chemotherapy. Of 56 children with recurrent malignant astrocytoma who received conventional chemotherapy following initial progression, no patient survives. Differences in distributions of survival were not significant when stratified by surgical debulking (P = 0.39). However, for patients who were surgically debulked, the survival distributions are significantly different (P = 0.017). CONCLUSIONS: Myeloablative chemotherapy with autologous marrow rescue can produce durable remissions in children and young adults with recurrent malignant gliomas, in the setting of minimal residual tumor burden achieved surgically.

A phase I trial of temozolomide and lomustine in newly diagnosed high-grade gliomas of childhood.

A phase I trial was conducted to determine the maximum tolerated dose (MTD) of temozolomide given in combination with lomustine in newly diagnosed pediatric patients with high-grade gliomas. Response was assessed following two courses of therapy at the MTD. Temozolomide was administered to cohorts of patients at doses of 100, 125, 160, or 200 mg/m(2) on days 1-5, along with 90 mg/m(2) lomustine on day 1. Two courses of lomustine/temozolomide were given prior to radiation therapy (RT) and up to six courses were administered afterward. Thirty-two patients were enrolled. Dose-limiting myelosuppression was seen in two of three patients enrolled at the 200 mg/m(2) dose level. One of 14 patients in the expanded MTD cohort (160 mg/m(2)) experienced dose-limiting thrombocytopenia. After two courses at the MTD, one patient with a 5-mm enhancing nodule postoperatively had a complete response, one patient with a large residual temporal lobe glioblastoma had a partial response, and eight patients had stable disease. Several patients developed transient radiographic worsening after completing RT. Median 1- and 2-year overall survivals at the MTD were 60% +/- 13% and 40% +/- 13% with a median of 17.6 months. Thirteen of 20 patients (65%) who underwent MRI scans within 6 months prior to death developed metastatic disease. In conclusion, when administered with 90 mg/m(2) lomustine on day 1, the MTD of temozolomide is 160 mg/m(2)/day x 5. Radiographic changes following RT make determination of early tumor progression difficult. Metastatic disease is common prior to death.

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.

The effects of reactive species on the tumorigenic phenotype of human head and neck squamous cell carcinoma (HNSCC) cells.

Sustained inflammation up-regulates the reactive species (RS) generating enzymes inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). While clinical data show that levels of iNOS and COX-2 are increased in epithelium during the transformation of dysplasia to overt head and neck squamous cell carcinoma (HNSCC), the mechanisms by which their overexpression contributes to HNSCC development have not been completely delineated. This study assessed the effects of RS on parameters associated with the HNSCC tumorigenic phenotype inclusive of activation of NF-kappaB (in situ immunostaining and reporter assay) and production of proinflammatory and proangiogenic proteins (ELISA analyses). Our data, which show both reactive oxygen and nitrogen species activated NF-kappaB, and that all RS donors evaluated increased HNSCC cellular production of vascular endothelial growth factor, IL-8 and epidermal growth factor receptor proteins, imply inflammation associated RS promote HNSCC by their abilities to modulate intracellular signaling and affect gene expression.

Molecular mechanisms of GD3-induced apoptosis in U-1242 MG glioma cells.

An increasing amount of evidence indicates that the disialoganglioside GD3 is involved in apoptosis in many cell lines. Our previous studies demonstrated that endogenous GD3 expression induced apoptosis in U-1242 MG glioma cells transfected with the GD3 synthase gene (U1242MG-GD3 cells). In this paper, we present further investigations on the molecular mechanisms of GD3-induced apoptosis in this cell line. We found that endogenously synthesized GD3 localizes to the caveolae of this cell line, where it promotes the localization of death receptor 5 (DR5), tumor necrosis factor receptor-1 (TNF-R1), and Fas (Apo-1) to the caveolae. In addition, caspase-8 was translocated to the caveolar fraction and cleaved; the cleaved proteins were then re-located into the high density fractions. However, GD3 had no effect on the distribution of the adapter protein Fas-associated death domain (FADD). We conclude that GD3 functions as a regulatory molecule early in the extrinsic apoptosis pathway.

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.

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.

Phase II study of high-dose chemotherapy before radiation in children with newly diagnosed high-grade astrocytoma: final analysis of Children's Cancer Group Study 9933.

BACKGROUND: High-grade astrocytomas (HGA) carry a dismal prognosis and compose nearly 20% of all childhood brain tumors. The role of high-dose chemotherapy (HDCT) in the treatment of HGA remains unclear. METHODS: In a nationwide study, The Children's Cancer Group (CCG) prospectively evaluated 102 children with HGA and postoperative residual disease for efficacy and toxicity of four courses of HDCT before radiotherapy (RT). Patients were randomly assigned to one of three couplets of drugs: carboplatin/etoposide (Regimen A), ifosfamide/etoposide (Regimen B), or cyclophosphamide/etoposide (Regimen C). After HDCT, all patients were to receive local RT followed by lomustine and vincristine. Twenty-six patients were excluded after central neuroradiographic review (n = 8) or pathology review (n = 18). RESULTS: Of 76 evaluable patients (median age, 11.95 yrs; range, 3-20 yrs), 30 patients relapsed during HDCT, and 11 others did not complete HDCT because of toxicity. Nonhematologic serious toxicities were common (29%), and 21% of patients did not receive RT. Objective response rates were not associated with amount of residual disease and did not statistically differ between regimens: 27% (Regimen A), 8% (Regimen B), and 29% (Regimen C). Overall survival (OS) was 24% +/- 5% at 5 years and did not differ between groups. Median time to an event was longest for Regimen A (283 days compared with 83 and 91 days for Regimens B and C, respectively). The five-year, event-free survival (EFS) rate for all patients was 8% +/- 3% and 14% +/- 7% for Regimen A (P = 0.07). CONCLUSIONS: OS and EFS were not affected by histologic grade. Patients who responded to HDCT had a nominally higher survival rate (P = 0.03 for trend). The authors conclude that these commonly used HDCT regimens provide no additional clinical benefit to conventional treatment in HGA, regardless of the amount of measurable residual tumor.

Essential role of E2-25K/Hip-2 in mediating amyloid-beta neurotoxicity.

The ubiquitin/proteasome system has been proposed to play an important role in Alzheimer's disease (AD) pathogenesis. However, the critical factor(s) modulating both amyloid-beta peptide (Abeta) neurotoxicity and ubiquitin/proteasome system in AD are not known. We report the isolation of an unusual ubiquitin-conjugating enzyme, E2-25K/Hip-2, as a mediator of Abeta toxicity. The expression of E2-25K/Hip-2 was upregulated in the neurons exposed to Abeta(1-42) in vivo and in culture. Enzymatic activity of E2-25K/Hip-2 was required for both Abeta(1-42) neurotoxicity and inhibition of proteasome activity. E2-25K/Hip-2 functioned upstream of apoptosis signal-regulating kinase 1 (ASK1) and c-Jun N-terminal kinase (JNK) in Abeta(1-42) toxicity. Further, the ubiquitin mutant, UBB+1, a potent inhibitor of the proteasome which is found in Alzheimer's brains, was colocalized and functionally interacted with E2-25K/Hip-2 in mediating neurotoxicity. These results suggest that E2-25K/Hip-2 is a crucial factor in regulating Abeta neurotoxicity and could play a role in the pathogenesis of Alzheimer's disease.

Association between chromosome 1p and 19q loss and outcome in pediatric malignant gliomas: results from the CCG-945 cohort.

BACKGROUND: Results of recent molecular studies on malignant gliomas in adults showed that deletions within the short arm of chromosome 1 and/or the long arm of chromosome 19 identified a prognostically favorable subgroup of tumors that often respond to conventional chemotherapy. To determine if this association applies to pediatric malignant gliomas, we examined the correlation between 1p and 19q deletions and outcome in the cohort derived from the Children's Cancer Group study 945, the largest randomized trial of such tumors completed to date. METHODS: Archival histopathologic material yielded tissue of sufficient quality and quantity for genotyping in 121 specimens. Sections were examined histologically and targets that contained malignant glioma were isolated by microdissection and subjected to polymerase-chain-reaction-based amplification of microsatellite loci using fluorochrome-labeled primers, followed by capillary electrophoresis, and fluorescent fragment analysis. One hundred and seven specimens had 2 alleles for at least 1 of the 3 1p loci examined, and were therefore informative for determining loss of heterozygosity, defined as at least a twofold difference in fluorescence intensity between the paired allelic bands; 99 were informative at 19q. RESULTS: Thirty-two tumors (29.9%) had loss of heterozygosity involving 1p, 27 (28%) involving 19q, and 13 involving both, an incidence consistent with previous reports involving adult malignant gliomas. However, outcome analyses of the entire cohort found no favorable association between 1p loss, 19q loss, or the combination, and survival. Subset analysis disclosed no association with outcome in either arm of the study (which compared efficacy of 2 chemotherapeutic regimens) or in subgroups stratified by age, tumor location, or tumor histology. CONCLUSION: In contrast to recent observations of adult malignant gliomas, deletions involving chromosomes 1p or 19q did not predict a survival advantage in this series of pediatric high-grade gliomas, which might indicate that frequencies of various histologic and molecular subtypes of malignant gliomas differ between children and adults, and supports further efforts to identify prognostic indicators relevant to pediatric gliomas.

Combined modality therapy for poorly differentiated gliomas of the posterior fossa in children: a Children's Cancer Group report.

PURPOSE: To study the effectiveness of combined chemotherapy and radiotherapy for children with high-grade astrocytomas of the posterior fossa. PATIENTS AND METHODS: In the CCG-945 study, 250 patients were treated by members of the Children's Cancer Group (CCG). Sixteen children were randomly assigned to one of two chemotherapy regimens, vincristine, lomustine, and prednisone or '8-in-1', using the same involved-field irradiation in both. Six infants received 8-in-1 chemotherapy before involved-field irradiation. All pathologic specimens had central review. RESULTS: Twenty-two patients with an institutional diagnosis high-grade posterior fossa tumors received chemotherapy and/or irradiation. Fifteen were confirmed by central review to have high-grade gliomas. Overall survival for confirmed high-grade astrocytoma of the posterior fossa was approximately 36 +/- 13% at 5 years for the children (n = 11) and 25 +/- 15% at 5 years for the infants (n = 4). CONCLUSIONS: Involved-field irradiation with chemotherapy appeared to prevent extraneural and subarachnoid metastases. We also confirmed the rarity of the tumor (6% of patients registered). Further Phase III trials are necessary to improve survival in this aggressive tumor.

The influence of central review on outcome associations in childhood malignant gliomas: results from the CCG-945 experience.

To examine the influence of the pathology review mechanism on the results of analyses of therapeutic efficacy and biological prognostic correlates for pediatric high-grade gliomas, we evaluated the effects of using single-expert review or consensus review, as alternatives to institutional classification, in determining outcome results of a large randomized trial. The study group was the randomized cohort of Children's Cancer Group study 945, which compared efficacy of 2 chemotherapy regimens adjuvant to surgery and radiation. Trial eligibility required institutional histopathologic diagnosis of high-grade glioma. Sections of study tumors also were centrally reviewed, initially by a study review neuropathologist and subsequently by 5 neuropathologists, including the review pathologist. Reviews were independent, and reviewers were masked to clinical factors and outcomes, and consensus diagnoses of the panel were then established. Among 172 eligible patients, 42 tumors were classified as discordant on single-expert review and 51 on consensus review. Progression-free survival probabilities calculated for patients with tumors classified as high-grade gliomas by either single-expert or consensus review were inferior to those for the overall, institutionally diagnosed cohort. However, conclusions of the study regarding relative efficacy of treatment and clinical and molecular outcome correlates were unaffected by diagnosis method. Resection extent, proliferation index, and p53 expression were associated strongly with outcome, regardless of diagnosis method. However, comparisons between arms in which inclusion was determined by different review criteria for each arm caused spurious conclusions about efficacy differences between treatments. We conclude that the pathology review mechanism had little effect on within-trial comparisons of therapeutic effects or prognostic correlates in this randomized study, but strongly influenced survival distributions that were calculated for each treatment arm. These results support the implementation of expedited central review in therapeutic studies involving childhood malignant gliomas as a way to prospectively identify and exclude cases with discordant diagnoses and indicate the need for additional measures, such as molecular assessments, to increase the reproducibility of neuropathologic classification for these tumors.

Domain-dependent modulation of PDGFRbeta by ganglioside GM1.

The regulation of receptor tyrosine kinases (RTKs) is important in several cellular events, including proliferation, differentiation, and apoptosis. Gangliosides are sialic acid-containing glycosphingolipids that can regulate RTK activity. The addition of ganglioside GM1 to the medium of Swiss 3T3 fibroblasts inhibits both platelet-derived growth factor (PDGF)-mediated tyrosine phosphorylation of PDGF receptor beta (PDGFRbeta) and receptor-mediated endocytosis. However, GM1 did not affect PDGF-mediated receptor phosphorylation, neuritogenesis, or endocytosis in PC12 cells stably transfected with the gene for PDGFRbeta. The ability of GM1 to modulate PDGFRbeta in 3T3 cells but not in transfected PC12 cells indicates a cell context-dependent response. We hypothesized that this inhibition of PDGFRbeta by GM1 must map to one or more domains of the receptor. Thus, a chimeric receptor was created that possessed the extracellular and transmembrane domains of the nerve growth factor (NGF) receptor TrkA and the cytoplasmic domain of PDGFRbeta (TTbeta). In 3T3 cells transfected with the TTbeta construct, GM1 did not inhibit NGF-induced tyrosine phosphorylation of the chimeric receptor or of Erk1/2 in this cell line. GM1 still inhibited PDGF-mediated tyrosine phosphorylation of endogenous PDGFRbeta and of Erk1/2 in Swiss TTbeta cells. Thus, the cytoplasmic domain of PDGFRbeta is not required for GM1-dependent inhibition of PDGFRbeta in 3T3 cells. This suggests that the inhibition of PDGFRbeta by GM1 in Swiss 3T3 fibroblasts maps to either the extracellular and/or transmembrane domain of PDGFRbeta.

'Spindle cell oncocytoma' of the adenohypophysis: a tumor of folliculostellate cells?

We describe five primary tumors of the adenohypophysis featuring mitochondrion-rich spindle cells. The patient ages ranged from 53 to 71 years (mean 61.6 years); two were female. All presented with panhypopituitarism. Two also had visual field defect. On neuroimaging all tumors showed suprasellar extension and were indistinguishable from pituitary adenoma. None showed imaging or operative evidence of dural involvement. All were gross totally removed: four by transsphenoidal surgery and one by frontal craniotomy. Follow-up ranged from 2 to 68 months (mean 35.4 months). No recurrences were noted. The clinical workup was noncontributory in all but two patients: one (case no. 4) with an oncocytic thyroid adenoma and another (case no. 5) with squamous carcinoma of both the uterine cervix and of vocal cord. Histologically, the five tumors were composed mainly of fascicles of spindle cells with eosinophilic, granular cytoplasm. Mitoses were rare and necrosis was absent. Neoplastic cells were immunoreactive for vimentin, epithelial membrane antigen, S-100 protein, and galectin-3. Stains for pituitary hormones, synaptophysin, chromogranin, glial fibrillary acidic protein, cytokeratin CAM5.2, smooth muscle actin, CD34, and CD68 were negative. No thyroglobulin immunoreactivity was noted in the tumor of case no. 4. Ultrastructurally, the neoplastic cells contained numerous mitochondria with lamellar cristae. The neoplastic cells were linked by intermediate junctions and desmosomes. No secretory granules were noted. The histologic, immunohistochemical, and fine structural features of these tumors were unlike those of pituitary adenoma or any other primary sellar tumor. A derivation from adenohypophyseal folliculostellate cells is suggested.

Impact of proliferation index on outcome in childhood malignant gliomas: results in a multi-institutional cohort.

OBJECTIVE: Prognoses of pediatric high-grade gliomas are unpredictable, even when clinical and histological factors are taken into account. In preliminary studies with an institutional cohort of pediatric high-grade gliomas, we observed a strong association between outcome and proliferation index, as assessed by immunolabeling with the MIB-1 antibody. To determine whether this marker could provide prognostically useful information independent of tumor histology, we examined the prognostic usefulness of this marker in the multi-institutional cohort of Children's Cancer Group Study 945, the largest group of childhood high-grade gliomas analyzed to date. METHODS: The study group consisted of tumors within this cohort that were classified as high-grade gliomas on central review according to contemporary World Health Organization guidelines and that had sufficient histopathological material to permit proliferation index assessment. Paraffin-embedded sections were cut and processed, microwave antigen enhancement was used, and MIB-1 indices were calculated by percent labeling in approximately 2000 cells (5-10 high-power fields) in the areas with greatest labeling. To ensure that the review diagnostic classification and proliferation labeling index were assigned independently for each tumor, these analyses were performed by two different neuropathologists at separate institutions, and each was blinded to the results of the other. RESULTS: Ninety-eight tumors met eligibility criteria for this study. Among these high-grade gliomas, there was a strong association between MIB-1 labeling and patient outcome: 5-year progression-free survival was 33 +/- 7% in 43 patients whose tumors had MIB-1 indices of less than 18%, 22 +/- 8% in the 27 patients whose tumors had indices between 18 and 36%, and 11 +/- 6% in the 28 patients whose tumors had indices greater than 36% (P = 0.003). As anticipated, a strong association was also observed between histology and MIB-1 labeling index in these cases. Mean labeling indices were 19.4 +/- 2.66 for tumors classified as anaplastic astrocytoma versus 32.1 +/- 3.08 for those classified as glioblastoma multiforme (P = 0.0024). Notwithstanding this correlation, a significant association was noted between labeling index and progression-free survival, even after the analysis had been stratified by histology (P = 0.001). Although histology had an independent association with outcome, the prognostic value of MIB-1 labeling transcended histological subgrouping and was apparent both in tumors classified as anaplastic astrocytoma (P = 0.02) and in those classified as glioblastoma multiforme (P = 0.046). Multivariate regression modeling confirmed the strong independent association between MIB-1 labeling index and outcome. As a group, tumors with labeling indices higher than 36% had an almost uniformly poor outcome, regardless of histology. CONCLUSION: MIB-1 labeling index and histological categorization are each prognostically relevant in childhood high-grade gliomas. MIB-1 labeling index can help to refine the accuracy of histologically based prognostic assessments.