Angiogenic profile of childhood primitive neuroectodermal brain tumours/medulloblastomas

Primitive neuroectodermal brain tumours (PNET) including medulloblastomas (PNET/MB) are the most common malignant brain tumours of childhood. Similar to many other brain tumours, PNET/MB often show marked neovascularisation. To determine which angiogenic factors contribute to PNET/MB angiogenesis, we examined the expression of eight angiogenic factors (vascular endothelial growth factors (VEGF, VEGF-B, VEGF-C), basic fibroblast growth factor (bFGF), angiopoetins (Ang-1, Ang-2), transforming growth factor (TGF-alpha), and platelet-derived endothelial growth factor (PDGF-A)) by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in six PNET cell lines and 28 primary PNET/MB. Expression levels of angiogenic factors were compared with microvessel density, TrkC mRNA expression, clinical variables and survival outcomes. Our results indicate that all PNET/MB tested produce a wide range of angiogenic factors that are, individually or together, likely to play a direct role in PNET/MB tumour growth. This suggests that anti-angiogenesis approaches targeting VEGF alone may be insufficient in PNET/MB.

MYC messenger RNA expression predicts survival outcome in childhood primitive neuroectodermal tumor/medulloblastoma

PURPOSE AND EXPERIMENTAL DESIGN

Cerebellar primitive neuroectodermal tumors/medulloblastomas (PNET/MB) are the most common malignant brain tumors in childhood. To identify PNET/MB biological prognostic factors that define a patient group with a sufficiently good prognosis to permit a reduction in treatment intensity, we determined the expression levels of MYC mRNA in fresh frozen tumor samples from 26 PNET/MB patients using semiquantitative reverse transcription-PCR.

RESULTS

MYC mRNA expression levels in primary PNET/MB showed a wide range with a 22-fold difference between the highest and lowest values and did not correlate with MYC gene amplification. MYC mRNA expression was an independent significant prognostic factor for progression-free survival outcome and was more predictive than standard clinical factors. The combination of low MYC mRNA expression and high TrkC mRNA expression identified a good outcome group of PNET/MB patients (n = 7) with 100% progression-free survival after a median follow-up time of 55 months (range, 15-91 months). Three of these seven good outcome patients survived without radiotherapy.

CONCLUSIONS

Low MYC mRNA expression is a powerful independent predictor of favorable clinical outcome in PNET/MB. Assessment of MYC mRNA levels is feasible and may be incorporated in prospective PNET/MB clinical trials to aid in treatment planning for patients with PNET/MB on confirmation of our results in larger studies.

Visual loss in children with neurofibromatosis type 1 and optic pathway gliomas: relation to tumor location by magnetic resonance imaging

PURPOSE

To examine the potential for visual acuity loss, and its relation to extent and location of optic pathway gliomas in a cohort of children with neurofibromatosis type 1 studied with magnetic resonance imaging.

METHODS

We reviewed the neuro-ophthalmologic records and brain/orbital magnetic resonance imaging scans for 43 consecutive pediatric patients with neurofibromatosis type 1 and optic pathway gliomas who were followed at the Children's Hospital of Philadelphia. The presence of visual loss, defined as abnormal visual acuity for age in one or both eyes, was determined. Optic pathway gliomas were classified by tumor extent and location according to involvement of the optic nerves, chiasm, and postchiasmal structures by magnetic resonance imaging.

RESULTS

Involvement of the optic tracts and other postchiasmal structures at tumor diagnosis was associated with a significantly higher probability of visual acuity loss (P =.048, chi-square test). Visual loss was noted in 20 of 43 patients (47%) at a median age of 4 years; however, three patients developed visual acuity loss for the first time during adolescence.

CONCLUSIONS

In pediatric patients with neurofibromatosis type 1 and optic pathway gliomas, the likelihood of visual loss is dependent on the extent and location of the tumor by magnetic resonance imaging and is particularly associated with involvement of postchiasmal structures. Furthermore, older age during childhood (adolescence) does not preclude the occurrence of visual loss. Close follow-up beyond the early childhood years, particularly for those with postchiasmal tumor, is recommended.

High microvessel density in primitive neuroectodermal brain tumors of childhood

Microvessel density (MVD), a measure of tumor angiogenesis, has been shown to correlate significantly with overall and progression-free survival outcomes in various cancers including astrocytic brain tumors. To assess if the MVD is an independent prognostic factor in primitive neuroectodermal tumors (PNET) of the central nervous system, formalin-fixed paraffin-embedded tumor sections of 78 children with PNET were studied by CD34 immunohistochemistry to highlight endothelial cells. Microvessel density was determined in the most active area of neovascularization according to well-established methods. While it was shown that MVD showed considerable inter-tumor variability (median 75; range 20-345 microvessels per 0.7 mm2 field), no significant associations were found between MVD and metastasis or survival outcomes. We conclude that many PNETs are highly vascular CNS tumors, indicating potent angiogenic activity. Therefore, these tumors would be good candidates for antiangiogenic strategies. However, MVD determined in the most active area of neovascularization is not a predictor of metastatic potential or survival outcomes in childhood PNET.

Antitumor activity of the rapamycin analog CCI-779 in human primitive neuroectodermal tumor/medulloblastoma models as single agent and in combination chemotherapy

We examined the cytotoxicity of the immunosuppressant agent rapamycin and its analogue CCI-779 in human brain tumor cell lines in vitro and in vivo as single agents and in combination with standard chemotherapeutic drugs. In the rapamycin-sensitive PNET/MB cell line DAOY, rapamycin exhibited additive cytotoxicity with cisplatin and with camptothecin. In vivo, CCI-779 delayed DAOY xenograft growth by 160% after 1 week and 240% after 2 weeks of systemic treatment, compared with controls. Single high-dose treatment induced 37% regression of tumor solume. Growth inhibition of DAOY xenografts was 1.3 times greater after simultaneous treatment with CCI-779 and cisplatin than after cisplatin alone. Interestingly, CCI-779 also produced growth inhibition of xenografts derived from U251 malignant glioma cells, a human cell line resistant to rapamycin in vitro. These studies suggest that the rapamycin analogue CCI-779 is an important new agent to investigate in the treatment of human brain tumors, particularly PNET/MB.

Reversible posterior leukoencephalopathy during the treatment of acute lymphoblastic leukemia

Three children with acute lymphoblastic leukemia developed altered mental status, headaches, seizures, and visual changes associated with reversible posterior cerebral changes on MRI. These clinical and radiologic findings were consistent with the reversible posterior leukoencephalopathy syndrome, which has not been widely recognized in this setting.

Prognostic significance of Ki-67 (MIB-1) proliferation index in childhood primitive neuroectodermal tumors of the central nervous system

BACKGROUND

Primitive neuroectodermal tumors (PNET) of the central nervous system, including medulloblastomas, are the most common malignant brain tumors of childhood. Whereas some patients experience prolonged disease control after surgery and adjuvant therapy, others with tumors that appear comparable will relapse and eventually die from progressive disease.

PROCEDURE

Because proliferative activity may provide a potential correlate of biologic aggressiveness, PNETs of 78 well-characterized patients were evaluated by Ki-67 (MIB-1) immunohistochemistry. Proliferation indices (PI) were determined by counting Ki-67 (MIB-1) positive tumor cells either in the highest staining region (hot spot PI), or in at least 15 randomly chosen fields (random PI).

RESULTS

Twenty-five of 78 PNETs showed amore than twofold higher value of hot spot PI (median 9.3%; range 0.6-56%), compared to random PI (median 5.6%; range 0.2-41.3%), Univariate Cox regression analysis revealed that PNETs with a high hot spot PI had a significantly greater risk of progression and death than PNETs with a low hot spot PI (hazard ratio 1.58, P = 0.04). The hazard ratio remained significant after adjusting for M-stage in multivariate analysis. In contrast to hot spot PI, random PI proved not to be a significant prognostic predictor.

CONCLUSIONS

Hot spot PI is a significant and independent prognostic factor in PNETs. Its assessment is uncomplicated, reliable, and may supplement routine histologic examination as a means for improving the accuracy of predicting the biologic behavior of childhood PNETs.

Growth hormone replacement therapy in children with medulloblastoma: use and effect on tumor control

PURPOSE

Progress has been made in the treatment of medulloblastoma, the most common childhood malignant brain tumor: However, many long-term survivors will have posttherapy growth hormone insufficiency with resultant linear growth retardation. Growth hormone replacement therapy (GHRT) may significantly improve growth, but there is often reluctance to initiate GHRT because of concerns of an increased likelihood of tumor relapse.

PATIENTS AND METHODS

This study retrospectively reviewed the use of GHRT for survivors of medulloblastoma in 11 neuro-oncology centers in North America who received initial treatment for disease between 1980 and 1993 to determine its impact on disease control. A Landmark analysis was used to evaluate the relative risk of relapse in surviving patients.

RESULTS

Five hundred forty-five consecutive patients less than 15 years of age at diagnosis were identified. Six-year progression-free survival (mean +/- SD) was 40% +/- 5% in children less than 3 years of age at diagnosis compared with 59% +/- 3% for older patients. Older patients with total or near-total resections (P = .003) and localized disease at diagnosis (P < .0001) had the highest likelihood of survival. One hundred seventy patients (33% +/- 3% of the cohort) received GHRT. GHRT use varied widely among institutions, ranging from 5% to 73%. GHRT was begun a mean of 3.9 years after diagnosis, later in children younger than 3 years at diagnosis (5.4 years). By Landmark analyses, for those surviving 2, 3, and 5 years after diagnosis, there was no evidence that GHRT increased the rate of disease relapse.

CONCLUSION

This large retrospective review demonstrates that GHRT is underutilized in survivors of medulloblastoma and is used relatively late in the course of the illness. GHRT is not associated with an increased likelihood of disease relapse.

Decreased cyclin B1 expression contributes to G2 delay in human brain tumor cells after treatment with camptothecin

DNA damage produces delayed mitosis (G2/M delay) in proliferating cells, and shortening the delay sensitizes human malignant glioma and medulloblastoma cells to cytotoxic chemotherapy. Although activation of the cyclin-dependent kinase CDC2 mediates G2/M transition in all tumor cells studied to date, regulation of CDC2 varies between tumor types. Persistent hyperphosphorylation of kinase and reduced cyclin expression have been implicated as mediators of treatment-induced G2 delay in different tumor models. To evaluate regulation of G2/M transition in human brain tumors, we studied the expression and/or activity of CDC2 kinase and cyclins A and B1 in U-251 MG and DAOY medulloblastoma cells after their treatment with camptothecin (CPT). Synchronized cells were treated during S phase, then harvested at predetermined intervals for evaluation of cell cycle kinetics, kinase activity mRNA, and protein expression. CPT produced G2 delay associated with decreased CDC2 kinase activity and cyclin B1 expression. Kinase activity was associated with CDC2 bound to cyclin B1, not cyclin A, in both cell lines. Cyclin A mRNA and protein expression were reduced after CPT treatment; however, decreased protein expression was short lived and moderate in the glioma and primitive neuroectodermal tumor/medulloblastoma cells, respectively. We conclude that G2 delay is a common response of brain tumor cells to chemotherapy with topoisomerase I inhibitors and that a mechanism of this delay may be reduced expression of cyclin B1.

Abundance of apoptotic neoplastic cells in diagnostic biopsy samples is not a prognostic factor in childhood primitive neuroectodermal tumors of the central nervous system

PURPOSE

To assess if the abundance of apoptotic tumor cells is an independent prognostic factor in primitive neuroectodermal tumors (PNET) of the central nervous system.

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded tumor tissue sections from 78 clinically well-characterized children with PNET were evaluated by terminal deoxytransferase-mediated deoxyuridinie-5'-triphosphate (dUTP) nick-end labeling (TUNEL). Apoptotic indices (AI) were determined by counting TUNEL-positive tumor cells either in the highest staining region (AI hot spot) or in at least 15 randomly chosen fields (AI random). The AI hot spot and AI random were then correlated with clinical variables and survival outcome.

RESULTS

AI hot spot (median 0.56%; range 0%-6.54%) and AI random (median 0.30%; range 0%-3.21%) showed considerable intertumor variability. Moreover, 53% of the evaluated PNET showed a more than two-fold difference between AI hot spot and AI random, showing important intratumoral variability of the abundance of apoptotic cells in a subset of the evaluated PNET. No significant associations were found between AI hot spot and AI random with clinical variables or survival outcome.

CONCLUSION

The apoptotic index does not predict survival outcome and is not specifically associated with clinical variables of prognostic significance in childhood PNET.

Resistance to TRAIL-induced apoptosis in primitive neuroectodermal brain tumor cells correlates with a loss of caspase-8 expression

TNF-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in adult malignant glioma and various other human solid tumor models but not in normal tissues. To characterize the TRAIL death pathway in childhood primitive neuroectodermal brain tumor (PNET), 8 human PNET cell lines were tested for TRAIL-induced apoptosis. TRAIL-sensitivity of the PNET cell lines was correlated with mRNA expression levels of TRAIL, its agonistic (TRAIL-R1, TRAIL-R2) and antagonistic (TRAIL-R3, TRAIL-R4) receptors, cellular FLICE-like inhibitory protein (cFLIP), caspase-3 and caspase-8. Three of 8 PNET cell lines tested were susceptible to TRAIL-induced apoptosis. Sensitivity to TRAIL-induced apoptosis did not correlate with mRNA expression of TRAIL receptors or cFLIP. However, all TRAIL-sensitive PNET cell lines expressed caspase-8 mRNA and protein, while none of the five TRAIL-resistant PNET cell lines expressed caspase-8 protein. Treatment with the methyltransferase inhibitor 5-aza-2'-deoxycytidine restored mRNA expression of caspase-8 and TRAIL-sensitivity in formerly TRAIL-resistant PNET cells, suggesting that gene methylation inhibits caspase-8 transcription in these cells. We conclude, that loss of caspase-8 mRNA is an important mechanism of TRAIL-resistance in PNET cells. Treatment with recombinant soluble TRAIL, possibly in combination with methyltransferase inhibitors, represents a promising therapeutic approach for PNET that deserves further investigation.

Neurotrophin receptor TrkC predicts good clinical outcome in medulloblastoma and other primitive neuroectodermal brain tumors

BACKGROUND

Neurotrophins and their cognate receptors TrkA, TrkB and TrkC regulate proliferation, differentiation and death of neuronal progenitor cells and may be implicated in the progression of medulloblastoma and other primitive neuroectodermal brain tumors (PNET). These common childhood brain tumors are composed of morphologically undifferentiated cells that have important similarities to neuroectodermal progenitor cells of the developing CNS.

PATIENTS AND METHODS

To identify biologic prognostic factors in childhood PNET we determined expression levels of TrkC mRNA in tumor samples from 87 PNET patients by in situ hybridization. Comparison of TrkC mRNA expression levels with clinical variables was performed using univariate and multivariable Cox regression analysis.

RESULTS

Cox regression analysis revealed that children with tumors expressing no or little TrkC mRNA had a 4.8-fold (p < 0.00005) greater risk of death than children with tumors with high TrkC mRNA expression. This hazard ratio remained consistent after adjusting for clinical variables. Five-year survival was 89% for patients with PNETs expressing high levels of TrkC mRNA and 47% for patients with PNETs expressing little or no levels of TrkC mRNA (log rank; p < 0.00005).

CONCLUSIONS

The TrkC neurotrophin receptor appears to be a powerful independent prognostic factor in PNET and may have a role in patient assignment to risk-based treatment strategies.

Mutations of the INI1 rhabdoid tumor suppressor gene in medulloblastomas and primitive neuroectodermal tumors of the central nervous system

Germ-line and somatic mutations of the hSNF5/INI1 gene have been reported in atypical teratoid/rhabdoid tumors (AT/RTs) of the brain, consistent with its role as a tumor suppressor gene. In the present study, we determined the frequency of deletions and mutations of INI1 in 52 children whose original diagnosis was medulloblastoma (MB) or primitive neuroectodermal tumor (PNET) of the central nervous system. Mutations were detected in DNA isolated from four tumors, all from children less than 3 years of age at diagnosis. Two of the four were reviewed and reclassified as atypical teratoid tumor, whereas there was insufficient material to establish this diagnosis in the two remaining cases. The relatively low frequency of mutations, even in a large series of infants, suggests that loss of sequences from chromosome 22 and/or mutations of INI1 do not account for the poor prognosis of children with MB or PNET who are less than 3 years of age at diagnosis. Nevertheless, chromosome 22 deletion and INI1-mutation analysis of infants with MB/PNET should be considered for all children who are less than 1 year of age. Detection of these mutations suggests that the child has an AT/RT, rather than a MB/PNET, a finding with important prognostic value.

Outcome for children with supratentorial primitive neuroectodermal tumors treated with surgery, radiation, and chemotherapy

BACKGROUND

The outcome of a child with a primitive neuroectodermal tumors arising supratentorially (SPNET) is not well characterized and may differ from the outcome of a patient with a histologically similar cerebellar tumor (medulloblastoma [MB]). Recently, 5-year progression free survival rates as high as 80% have been reported for children with MB treated with craniospinal radiation (CRT) and chemotherapy including cisplatin, lomustine (CCNU), and vincristine (VCR).

METHODS

The authors reviewed the outcome of 22 consecutive patients age 3 years and older (mean age, 10 years; range, 3-18 years) with SPNET who were treated at the study institutions between 1981 and 1996. Tumor location included was 13 pineal, 6 cortical, and 3 thalamic or suprasellar. Five patients had disease dissemination at diagnosis. All patients underwent surgery and staging, followed by CRT and chemotherapy with cisplatin, CCNU, and VCR.

RESULTS

Of the 22 patients, 13 had developed disease progression and 10 had died at the time of last follow-up. Overall progression free survival (PFS) was 47% +/- 11% at 3 years and 37% +/- 11% at 5 years. There was a significant difference in PFS between patients with localized disease versus those with disseminated disease (P = 0.04). There was no statistical association between tumor location and survival. Although not significant (P = 0.21), there was a trend toward better survival of those patients with complete or near-complete resection compared with those with partial resection or biopsy.

CONCLUSIONS

The results of the current study demonstrate that the outcome for children with SPNET treated with radiation and chemotherapy appears worse than for children with MB treated with identical therapy. This suggests that there may be biologic differences between supratentorial and infratentorial primitive neuroectodermal tumors, thus requiring refinements in treatment.

TrkC expression predicts good clinical outcome in primitive neuroectodermal brain tumors

PURPOSE

To identify biologic prognostic factors in childhood primitive neuroectodermal tumors (PNET), including medulloblastoma, that accurately define patient groups with sufficiently good prognosis to permit a reduction in treatment intensity.

PATIENTS AND METHODS

We determined expression levels of the neurotrophin receptor TrkC mRNA in formalin-fixed tumor samples from 87 well characterized PNET patients using in situ hybridization. Comparison of TrkC mRNA expression levels with clinical and other laboratory variables was performed using univariate and multivariate Cox regression analysis.

RESULTS

High TrkC mRNA expression was found to be associated more with higher 5-year cumulative survival rate than was low TrkC mRNA expression (89% v 46%, respectively). When compared with established clinical prognostic factors and laboratory variables of potential prognostic significance, TrkC mRNA expression, by univariate analysis, was found to be the single most powerful predictor of outcome (hazards ratio, 4.81; P <.00005), exceeding all clinical prognostic factors. In multivariate analysis, the hazards ratio remained significant (P <.00005).

CONCLUSION

High TrkC mRNA expression in PNET is a powerful independent predictor of favorable clinical outcome. Assessment of TrkC mRNA levels may aid in treatment planning for patients with PNETs and should be incorporated prospectively into PNET clinical trials.

Quality of life of adult survivors of germinomas treated with craniospinal irradiation

OBJECTIVE

To assess the quality of life (QOL) of a group of patients treated for intracranial germinoma with biopsy followed by prophylactic whole-neuraxis radiation therapy.

METHODS

The Short-form-36 and Functional Assessment of Cancer Therapy QOL questionnaires were completed by 22 of 27 eligible adults treated with whole-neuraxis irradiation for biopsy-proven, marker-negative intracranial germinomas between 1976 and 1996. In addition, data were obtained regarding height and weight, medications, ability to work, and educational achievement.

RESULTS

The patients' QOL was generally good. All of the patients are in or have completed high school; nine are in or have completed college, and five have advanced degrees. Patients rated themselves lower on the physical composite scale of the Short-form-36 (average, 46 versus 54 in a normal population). On the mental composite scale, patients rated themselves more favorably than the normal population (average, 54 versus 49 in a normal population). Patients were normally proportioned for height and weight, but female patients tended to be short. Age at radiation did not correlate with QOL.

CONCLUSION

The QOL of adults treated for marker-negative germinoma with prophylactic whole-neuraxis irradiation is generally good. These data should serve as a benchmark for newer treatment protocols eliminating or reducing radiation.

Caffeine and staurosporine enhance the cytotoxicity of cisplatin and camptothecin in human brain tumor cell lines

Caffeine and staurosporine have been shown to attenuate G2 delay produced by DNA-damaging agents and to augment the cytotoxicity of these agents in a number of cell lines in vitro. Studies in rodent brain tumor cell lines suggest that modulation of the G2/M transition may not contribute to the enhanced cytotoxicity produced by caffeine in brain tumor cells. To evaluate the impact of agents that decrease G2 delay on the cytotoxicity of chemotherapy in human brain tumor cells, we examined the ability of caffeine and staurosporine to modulate the G2 delay and cytotoxicity produced by cisplatin (CDDP) and camptothecin (CPT) in U251 glioma and DAOY medulloblastoma cells. Synchronized U251 were incubated with 20 microM CDDP in the presence or absence of 2 mM caffeine. DAOY cells were incubated with 100 nM CPT in the presence or absence of 2 nM staurosporine. Caffeine and staurosporine attenuated G2 delay produced by CDDP and CPT, respectively. Clonogenic assays indicated that continuous exposure to 2 mM caffeine substantially lowered the ID50 and ID90 of CDDP in U251 cells without significantly altering plating efficiency. Twenty-four-hour exposure to 2 nM staurosporine lowered the ID50 and ID90 of CPT in DAOY cells without significantly altering plating efficiency. Evaluation of programmed cell death using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assay indicated that one mechanism for synergistic cytotoxicty of caffeine with CDDP and staurosporine with CPT in U251 and DAOY cells, respectively, is to promote apoptosis. These results underscore the importance of understanding regulation of G2/M transition in brain tumor cells. Such an understanding may lead to novel therapies that target G2 check points to augment the efficacy of currently available treatments for brain tumors.

Synergistic cytotoxicity of topoisomerase I inhibitors with alkylating agents and etoposide in human brain tumor cell lines

To evaluate potential synergistic interactions between topoisomerase I (Topo I) inhibitors, i.e. camptothecin (CPT) and topotecan (TPT), and chemotherapeutic agents known to be active in treatment of brain tumors, in vitro studies were conducted with human glioma and medulloblastoma cell lines. Tumor cells were exposed to CPT or TPT alone or in combination with cisplatin, 4-hydroperoxycyclophosphamide (4-HC), BCNU or etoposide (VP-16). Cytotoxicity was assessed by colony formation assays. Drug interactions were evaluated by means of a novel analytical model which permits statistical evaluation over a range of dose combination. Experimental results were corroborated by published models of drug interaction. Our findings indicate that in vitro cytotoxic interactions in brain tumor cells between Topo I inhibitors and alkylating agents or etoposide depend on drug dose, dose schedule and tumor cell line. Treatment of DAOY medulloblastoma cells with CPT and either cisplatin, 4-HC or VP-16 produced significant synergistic cytotoxicity over a wide range of dose combinations. When VP-16 was administered after CPT, synergy was reduced to a narrow range of dose combinations. For U251 glioma cells, incubation with CPT and cisplatin or 4HC also produced synergistic cytotoxicity over a broad range of dose combinations. By contrast, antagonistic interactions were observed after administration of CPT with BCNU or VP-16. Treatment of U251 cells with CPT and cisplatin produced synergistic or antagonistic cytotoxicity depending on the dose combination used. These findings support a role for pharmacokinetic analysis in multiagent phase 11 trials involving Topo I inhibitors and have important implications for clinical trial design strategies.

Prognostic significance of chromosome 17p deletions in childhood primitive neuroectodermal tumors (medulloblastomas) of the central nervous system

Deletions in the short arm of chromosome 17 (17p) are the most common genetic abnormality in primitive neuroectodermal tumors of the posterior fossa/medulloblastoma (PNET/Mb). The biological consequences of these deletions are not known for children with PNET/Mb; however, the presence of a tumor suppressor gene located in 17p, distinct from p53, has been implicated in tumorigenesis. Two recent studies suggest that 17p deletions in PNET/Mb are associated with a poor prognosis. To address this question, we identified deletions of chromosome 17p by cytogenetic and/or molecular biology methods in tumor biopsy samples from 56 patients with PNET/Mb. Associations between clinical characteristics or survival outcomes and 17p status were examined by multivariate analysis. Forty-one percent of PNET/Mb cases had a deletion of 17p. No significant association was found between 17p deletion and shorter survival duration or higher metastatic stage. Multivariate analysis did not find independent prognostic significance for 17p deletions after accounting for the effects of significant clinical variables. A larger study of the prognostic value of 17p deletion should be considered; however, clinical use of this factor to distinguish high-risk from standard-risk PNET/Mb populations is not warranted at this time.

Glial differentiation predicts poor clinical outcome in primitive neuroectodermal brain tumors

Primitive neuroectodermal tumors (PNETs) of the central nervous system, including medulloblastomas (PNET/MB), are the most common malignant brain tumor of childhood. These tumors often express proteins characteristic of glial differentiation (glial fibrillary acidic protein, GFAP), neuronal differentiation (neurofilament proteins, NFPs), and/or photoreceptor differentiation (retinal-S antigen). To identify biological factors of prognostic significance in PNETs, the expression of glial, neuronal, or photoreceptor antigens was evaluated in the tumor specimens of 86 patients with PNETs by immunohistochemistry after microwave antigen enhancement. Patterns of differentiation were then compared with patient relapse-free survival. Multivariate analysis of PNET immunohistochemistry and clinical variables indicated GFAP expression conferred a 6.7-fold greater risk of relapse than tumors that did not express GFAP or NFPs. Increased risk of relapse was directly related to the amount of GFAP expression. Tumors exhibiting clumps or sheets of GFAP-staining cells were associated with a 3.0-fold increased risk of relapse compared with tumors that did not express GFAP, irrespective of immunohistochemical evidence of other differentiation, while scattered GFAP staining was not associated with increased risk of relapse. These findings indicate that expression of GFAP in PNETs has prognostic power comparable with the most significant clinical factors currently used to predict clinical outcome.

Isochromosome 17q demonstrated by interphase fluorescence in situ hybridization in primitive neuroectodermal tumors of the central nervous system

We previously reported an i(17q) as a non-random finding in childhood primitive neuroectodermal tumors (PNETs) of the central nervous system. In the present study, we describe a two-color interphase fluorescence in situ hybridization (FISH) assay for detection of chromosome 17 abnormalities in tumors. Thirty-four PNETs were analyzed by FISH with a series of chromosome 17-specific probes which map to 17p13.3-17q25. The results from the FISH assay were then compared to the karyotypes prepared from the tumors. Ten of the 34 cases demonstrated an i(17q) by FISH and standard cytogenetics. Two PNETs were shown to have an i(17q) by FISH alone, and three additional tumors had deletions of 17p. Thus, a total of 15 of 34 (44%) of the PNETs in this series had a deletion of 17p. This study confirms and extends our previous reports that an i(17q) is the most common cytogenetic abnormality in PNETs. The interphase FISH assay which we employed will have clinical utility for diagnosis of children with malignant brain tumors, and it may be used for identification of tumors with 17p deletions for molecular studies aimed at identifying disease genes.

Optic pathway and hypothalamic/chiasmatic gliomas in children younger than age 5 years with a 6-year follow-up

BACKGROUND

Gliomas of the hypothalamus and optic pathways (H/OPG) comprise 5% of pediatric intracranial tumors, present most frequently in patients younger than age 5 years, and may have a more aggressive course in younger children. This study examined clinical characteristics and consequences of treatment of young children diagnosed with H/OPG:

METHODS

The authors reviewed the course, treatment, and outcomes of 46 children diagnosed with H/OPG younger than age 5 years; the median follow-up was 72 months. The median age at diagnosis was 27 months.

RESULTS

Fifteen (33%) of 46 patients had neurofibromatosis-1 (NF-1). Forty children (87%) had tumor progression in the follow-up period, and tumor growth was less common in children with NF-1. Initial therapy was limited to surgical resection in three and radiation in five children. To postpone radiation until after the age of 5 years, initial therapy was limited to chemotherapy in 32 patients. Radiation was not required in 9 of these patients and was postponed for 40 months (mean) in 17. Of the 46 children, 5 died of tumor progression, 4 became blind, and 20 of 34 evaluable patients had endocrine abnormalities. Endocrinopathy did not correlate with therapy. Ten of 17 children evaluated by questionnaire required special education. There was a trend for educational problems to occur in children who were irradiated before the age of 5 years.

CONCLUSIONS

Gliomas of the hypothalamus and optic pathways and their treatment cause long term morbidity in young children. Chemotherapy postpones radiation effectively, and this delay may reduce neurologic morbidity; however, 60% of children eventually relapse. By contrast, patients with NF-1 have indolent disease.

Superficial siderosis of the central nervous system: magnetic resonance imaging and pathological correlation. Case report

The authors report a 32-year-old woman who had undergone repair of an occipital encephalocele in infancy and who experienced a 20-year history of progressive hearing loss and intermittent vertigo. After parturition, she developed a rapidly progressive quadriparesis and brain-stem dysfunction associated with persistent intraventricular and subarachnoid hemorrhage. Serial magnetic resonance (MR) images showed progressive deposition of hemosiderin along the surface of the brain, brain stem, and spinal cord, and enhanced thickened membranes at the site of the original encephalocele repair. Posterior fossa exploration disclosed hemorrhagic membranes, which were resected; despite removal of this tissue, the patient deteriorated and died. Postmortem examination confirmed iron-containing pigment along the meninges, cerebral hemispheres, brain stem, spinal cord, and cranial nerves accompanied by atrophy of the superficial cerebellar cortex. It is concluded that superficial siderosis may accompany encephalocele repair. This is believed to be the first report in the literature of superficial siderosis of the central nervous system to correlate in vivo MR images with autopsy results.

Brainstem and spinal pathways mediating descending inhibition from the medullary lateral reticular nucleus in the rat

The lateral reticular nucleus (LRN) in the caudal ventrolateral medulla has been implicated in descending monoaminergic modulation of spinal nociceptive transmission. Experiments were undertaken to examine the organization of pontine and spinal pathways mediating inhibition of the tail-flick (TF) reflex from the LRN in rats lightly anesthetized with pentobarbital. Microinjections of the local anesthetic lidocaine ipsilaterally or bilaterally into the dorsolateral pons blocked stimulation-produced inhibition of the TF reflex from the nucleus locus coeruleus/subcoeruleus (LC/SC), but had no effect on descending inhibition produced by microinjection of glutamate into the LRN. Thus, adrenergic modulation of the TF reflex from the LRN is not mediated by activation of spinopetal noradrenergic neurons in the LC/SC. The funicular course of descending inhibition produced by focal electrical stimulation in the LRN was studied in separate groups of rats by reversibly (local anesthetic blocks) or irreversibly (surgical transection) compromising conduction in the dorsolateral funiculi (DLFs) at the level of the cervical spinal cord. Bilateral lidocaine blocks in the DLFs significantly shortened control TF latencies and more than doubled the intensity of electrical stimulation in the LRN necessary to inhibit the TF reflex (153 +/- 29% increase from control); changes in these parameters produced by unilateral blocks of the DLFs were not statistically significant. Ipsilateral or bilateral transections of the DLFs significantly increased the intensity of electrical stimulation in the LRN to inhibit the TF reflex (110 +/- 24% and 265 +/- 46% from control, respectively). Neither lidocaine blocks nor transections of the DLFs completely blocked the descending inhibitory effects of electrical stimulation in the LRN. The DLFs appear to carry fibers mediating LRN stimulation-produced inhibition of the TF reflex as well as tonic descending inhibition of spinal reflexes. The results of the present study indicate that (1) adrenergic modulation of the nociceptive TF reflex from the LRN does not depend on a rostral loop through the pontine LC/SC, and (2) descending inhibitory influences from the LRN are contained in, but not confined to, the dorsal quadrants of the spinal cord.

Quantitative characterization and spinal pathway mediating inhibition of spinal nociceptive transmission from the lateral reticular nucleus in the rat

1. The modulation of spinal nociceptive transmission from the lateral reticular nucleus (LRN) was characterized for 47 spinal dorsal horn neurons in pentobarbital-anesthetized, paralyzed rats. All 47 units studied had receptive fields confined to the glabrous skin of the plantar surface of the ipsilateral hind foot and responded to mechanical stimulation as well as noxious heating (50 degrees C). Rostral projections contained in the ventrolateral quadrant of the cervical spinal cord were demonstrated for 15 of the 47 units by antidromic invasion. Glutamate- and stimulation-produced descending inhibition, the spinal pathway, and tonic descending inhibition from the LRN were systematically examined. 2. Inhibition of unit responses to heating of the skin by electrical stimulation in the LRN varied with the intensity, pulse duration (100 or 400 microseconds), and frequency (25-100 Hz) of stimulation. Greater inhibition was produced at lower intensities of stimulation with the 400-microseconds pulse duration and a frequency of 100 Hz. The effects of stimulation on spontaneous activity and responses to heat were compared in 16 experiments; inhibition of spontaneous activity was intensity dependent and did not differ significantly in magnitude from stimulation-produced inhibition of responses to heating of the skin. 3. Tracking experiments established that stimulation in the ipsilateral and contralateral ventrolateral medulla reliably attenuated unit responses to noxious heating of the skin and that stimulation in the LRN produced maximal inhibition at a low intensity of stimulation. Descending inhibition was quantitatively characterized from sites within (n = 32) and outside (n = 30) the LRN. Both the extrapolated mean stimulation threshold for inhibition and mean intensity inhibiting unit responses to heat to 50% of control were significantly lower for sites in the LRN. 4. The responses of seven spinal units to graded noxious heating of the skin were studied; all exhibited linear monotonic stimulus-response functions (SRFs) throughout the temperature range examined (42-50 degrees C). Electrical stimulation in the LRN significantly decreased the slope (42 +/- 4% of control) of the SRFs and increased the neuronal response threshold (2.0 +/- 0.7 degrees C). 5. S-glutamate (50 nmol, 0.5 microliter) was microinjected into stimulation sites within (n = 15) and distant from (n = 6) the LRN. Glutamate produced a transient (less than 7 min) but significant attenuation of neuronal responses to heat to 35 +/- 6% of control only when microinjected into the LRN.(ABSTRACT TRUNCATED AT 400 WORDS)

Spinal monoaminergic receptors mediate the antinociception produced by glutamate in the medullary lateral reticular nucleus

Focal electrical stimulation and microinjection of the excitatory amino acid glutamate in the lateral reticular nucleus (LRN) both inhibit the heat-evoked tail flick (TF) reflex in rats. The stimulation-produced inhibition from the LRN has previously been demonstrated to be mediated by spinal monoaminergic receptors. In the present study, inhibition of responses to noxious thermal stimuli by glutamate microinjected into the LRN was examined and characterized; this study is the first to examine the spinal receptors mediating inhibition produced by selective activation of cell bodies in the LRN. Microinjection of glutamate (100 mM) into the LRN in rats lightly anesthetized with pentobarbital produced a transient (less than 5 min) inhibition of the heat-evoked TF reflex, the magnitude of which increased with the volume of glutamate injected (100, 200, or 400 nl). This glutamate-produced inhibition of the TF reflex was antagonized by the intrathecal administration of phentolamine (30 micrograms), yohimbine (15 and 30 micrograms), or methysergide (15 and 30 micrograms) to the level of the lumbar spinal cord, but was not antagonized by prazosin (30 micrograms) or naloxone (20 micrograms). Yohimbine (15 and 30 micrograms) administered to the level of the cervical spinal enlargement did not significantly alter inhibition of the TF reflex produced by glutamate microinjected into the LRN. Microinjection of glutamate (100 mM, 400 nl) into the LRN elevated TF latencies and hindpaw lick latencies in the hot plate test performed on conscious rats. This inhibition of responses to noxious thermal stimuli in conscious rats was short-lasting (less than 5 min), and was also attenuated by intrathecal administration of yohimbine (30 micrograms) or methysergide (30 micrograms), but not by prazosin (30 micrograms) or naloxone (20 micrograms). While it has previously been established that cell bodies in the LRN mediate descending inhibition of spinal nociceptive reflexes, the present results establish that spinal alpha 2-adrenoceptors and serotonin receptors mediate LRN-produced antinociception and extend our understanding of LRN-mediated modulation of nociceptive responses integrated spinally and supraspinally.

Dissociation of antinociceptive from cardiovascular effects of stimulation in the lateral reticular nucleus in the rat

The lateral reticular nucleus (LRN) in the caudal ventrolateral medulla has been implicated in the regulation of spinal nociceptive transmission and hemodynamics. Experiments were undertaken to examine the relationship between inhibition of the tail flick reflex and cardiovascular effects produced by electrical stimulation in the LRN in rats lightly anesthetized with pentobarbital. Intensity- and frequency-dependent increases in mean arterial pressure and vascular resistance in the hindquarter, mesenteric, renal and caudal arterial beds were observed. Inhibition of the tail flick reflex, however, occurred at intensities of electrical stimulation which produced no significant changes in mean arterial pressure or vascular resistance in any of the arterial beds studied. Selective stimulation of cell bodies in the LRN by microinjection of glutamate similarly inhibited the tail flick reflex but produced significant reductions in mean arterial pressure, without substantially affecting regional vascular resistances. These results suggest that the antinociceptive and depressor effects of stimulation in the LRN are mediated by activation of cell bodies, while pressor effects produced by focal electrical stimulation are mediated by activation of fibers of passage. The descending inhibition produced by stimulation in the LRN is independent of stimulation-produced cardiovascular responses.

Effect of spinal norepinephrine depletion on descending inhibition of the tail flick reflex from the locus coeruleus and lateral reticular nucleus in the rat

The lateral reticular nucleus (LRN) and locus coeruleus-subcoeruleus (LC/SC), brainstem structures which overlap the A1 and A6 noradrenergic nuclei respectively, have been implicated in descending modulation of spinal nociceptive transmission. The present studies were designed to examine the role of norepinephrine (NE) in the mediation of inhibition of the nociceptive tail flick reflex produced by focal electrical stimulation in the LRN and LC/SC. Spinal NE was depleted by intrathecal administration of 6-hydroxydopamine (6-OHDA; 20 micrograms) and the threshold electrical stimulation in the LRN and the LC/SC necessary to inhibit the tail flick reflex in lightly pentobarbital-anesthetized rats was determined 9 and 14 days later. Despite a significant depletion (greater than 85%) of lumbar spinal cord NE content, there was no significant change in the tail flick inhibitory stimulation thresholds in the LRN or LC/SC. NE depletion did, however, potentiate the elevation in the inhibitory stimulation threshold in the LRN produced by intrathecal administration of the alpha 2-adrenoceptor antagonist, yohimbine, suggesting that upregulation of spinal adrenoceptors had occurred following 6-OHDA treatment. Adrenoceptor up-regulation was examined quantitatively by characterizing the dose-dependent antinociceptive potency of the selective alpha 2-adrenoceptor agonist clonidine 3, 7, 10, and 14 days following 6-OHDA administration, and analysis of [3H]rauwolscine binding to lumbar spinal cord 9 days following administration of the neurotoxin. The development of supersensitivity, defined as the leftward parallel shift of the dose-response curves for clonidine administered intrathecally, corresponded to the time course of NE depletion following 6-OHDA treatment on the days tested. Binding of [3H]rauwolscine to lumbar spinal cord revealed an elevation in the estimated Bmax without a change in the estimated Kd of the high affinity binding component 9 days following 6-OHDA administration. This study demonstrates that spinal adrenoceptor denervation supersensitivity develops rapidly following intrathecal administration of 6-OHDA and compensates for the selective destruction of spinal noradrenergic nerve terminals. Thus, the absence of effect of NE depletion on the tail flick inhibitory stimulation threshold in the LRN and the LC/SC does not argue against the hypothesis that spinopetal NE-containing neurons in these brainstem loci are involved in modulation of spinal nociceptive transmission.