1956

EGFR

ERBB|ERBB1|HER1|PIG61|mENA;epidermal growth factor receptor;EGFR;epidermal growth factor receptor

avian erythroblastic leukemia viral (v-erb-b) oncogene homolog|cell growth inhibiting protein 40|cell proliferation-inducing protein 61|proto-oncogene c-ErbB-1|receptor tyrosine-protein kinase erbB-1

7p12

protein-coding

Although common among adult intracranial neoplasms, pediatric malignant astrocytomas (PMAs) comprise a relatively small proportion of the brain tumors that occur in children. The scarcity of such cases generally requires that molecular analyses of PMAs are based on the utilization of paraffin-embedded material, and here we have used 39 such specimens to examine the incidence and prognostic significance of oncogene and tumor suppressor gene alterations (including amplifications of EGFR, CDK4, and MDM2 as well as inactivating mutations of CDKN2A, TP53, and PTEN) in these tumors. In general, the frequency of alteration for the genes we have studied fell within ranges that have been reported for adult astrocytomas. However, EGFR amplification, which is usually observed in approximately 40% and 15% of adult grade 4 and grade 3 astrocytomas,respectively, was not detected in any member of this series. With regard to prognosis, PTEN mutations were significantly associated with decreased survival among grade 3 and grade 4 PMA patients, a potentially important observation because neither patient age nor tumor malignancy grade was correlated with outcome for these individuals. In total, our data suggest at least one significant distinction between the genetic etiology of pediatric and adult astrocytomas and additionally reveal that analysis of PTEN mutations in PMA patients may be useful in the differential diagnosis of these tumors.

Amplification of the EGFR, mdm2, CDK4 and PDGFR A genes has been widely demonstrated in adult malignant gliomas, almost exclusively glioblastomas. To determine the role of these mutational events in pediatric astrocytic gliomas weinvestigated the presence of EGFR, mdm2, CDK4 and PDGFR A gene amplification in 38 childhood brain tumor biopsies, including 24 low-grade astrocytomas and 14 malignant tumors. We used differential PCR assay on DNA extracted either from paraffin embedded or frozen tissues. EGFR gene amplification was detected in 4 out of 14 malignant tumors; no low-grade astrocytoma showed amplification. tumors with EGFR gene amplification were negative for the presence of p53 mutations, asobserved in a previous study. One glioblastoma showed PDGFR A amplification, while no amplifications were observed for mdm2 and CDK4 genes. These data are inline with those obtained from studies on gliomas of adults and suggest the existence of two different subsets of malignant gliomas also in pediatric brain tumors: one carrying EGFR gene amplification, the other showing p53 mutations.

Intense angiogenesis proliferation, a histopathological hallmark distinguishing malignant from benign astrocytoma, is vital for tumor progression. Thus, identifying and targeting specific pathways that promote malignant astrocytoma-induced angiogenesis could have substantial therapeutic benefit. expression profiling of 13 childhood astrocytomas to determine the expression pattern of 133 angiogenesis-related genes revealed that 44 (33%) genes were differentially expressed (17 were overexpressed, and 27 were underexpressed) between malignant high-grade astrocytomas (HGAs) and benign low-grade astrocytomas. Hierarchical clustering and principal components analysis using only the 133 angiogenesis-related genes distinguished HGA from low-grade astrocytoma in 100% of the samples analyzed, as did unsupervised analyses using the entire set of 9198 expressed genes represented on the array, indicating thatthe angiogenesis-related genes were reliable markers of pathological grade. A striking new finding was significant overexpression of hypoxia-inducible transcription factor (HIF)-2alpha as well as high-level expression of FK506-binding protein (FKBP) 12 by HGA. Furthermore, 9 of 21 (43%) genes overexpressed by HGA were HIF/FKBP-associated genes. This group included the epidermal growth factor receptor (EGFR), which promotes HIF synthesis, as well as insulin-like growth factor-binding protein 2 (IGFBP2), a target gene of HIF activity. Differential protein expression of HIF-2alpha was validated in an independent group of 16 astrocytomas (P = 0.02). We conclude that the EGFR/FKBP12/HIF-2alpha pathway is important in childhood HGA and represents a potential new therapeutic target.

In the wake of recent progress in understanding the genetic pathways involved inthe development of brain tumors, a major goal is to correlate molecular data with clinical outcome, survival, and response to treatment modalities. This is of particular importance among the pediatric population. Reliable prognostic factors could potentially permit a tailoring of therapy in that only patients with the most aggressive tumors would receive the most intense treatments. A survey of publications about prognosis-related molecular features among pediatric brain tumors revealed 74 series, of which 46 presented statistically significant outcome-associated parameters as defined by a p value <0.05. Most investigationsrevealing significant prognosis-related features were performed on medulloblastomas (34 publications), followed by astrocytic tumors (6 publications) and ependymomas (5 publications). Promising approaches and molecular markers include gene expression profiles, DNA ploidy, loss of heterozygosity and chromosomal aberrations as detected by CGH and FISH (1q, 17p,17q), as well as oncogenes/ tumor suppressor genes and their proteins (TP53, PTEN, c-erbB2, N-myc, c-myc), growth factor and hormonal receptors (PDGFRA, VEGF, EGFR, HER2, HER4, ErbB-2, hTERT, TrkC), cell cycle genes (p27) and cell adhesionmolecules, as well as factors potentially related to therapeutic resistance (multi-drug resistance, DNA topoisomerase IIalpha, metallothionein, P-glycoprotein, tenascin). This review discusses the predictive potential of molecular markers for clinical outcome and their influence on therapeutic decision-making among children with brain tumors.

pediatric glioblastoma multiforme (GBM) tumors, which have been established as 'de novo' neoplasms, are known to differ from their adult counterparts in terms of biology, genetics and ultimately survival of patients. In order to evaluate the utility of markers of tumor biology for refining prognostic assessment, we retrospectively analyzed 54 pediatric GBMs (age range 9 months to 15 years) occurring at different anatomical sites in the brain, operated at our institute between 1995 and 2001. The expression of p53, epidermal growth factor receptor (EGFR), bcl-2 and retinoblastoma proteins (pRb) was analyzed by immunohistochemistry and the results were compared with the clinical profile, MIB-1 labeling index (LI) and patient survival. p53 immunoreactivity was noted in 53.7% of cases, predominantly in thalamic (75%) and cerebral lobar (62.2%), followed by brainstem tumors (30%). It was absent in cerebellar tumors. p53-positive tumors had a higher MIB-1 LI, compared to p53-negative tumors (p=0.003). EGFR and bcl-2 overexpression was observed in 25.9% and 33.3% of cases, respectively, and loss of pRb expression was evident in only 7.4% of cases, indicating that loss of this gene function is not significantly involved in pediatric GBMs. p53 and bcl-2 expression were maximally noted in patients with poorer outcome. Our results indicate that p53 expression status is noted in a significant number of pediatric supratentorial neoplasms. p53 with bcl-2 overexpression is more often associated with ominous prognosis. Further molecular characterization would provide newer insights into the biology of these neoplasms and form a basis for future therapeutic decision making.#CI- Copyright (c) 2005 S. Karger AG, Basel.

Papillary glioneuronal tumors (PGNTs) are rare lesions of the central nervous system, and no information exists on the genetic alterations in these neoplasms.The authors report on such a case in a child. Genetic studies revealed that the tumor was characterized by gains and structural alterations involving only chromosome 7 with breakpoints at 7p22. By using comparative genomic hybridization, the authors observed a high-level amplification region at 7p14~q12. Fluorescence in situ hybridization with a probe for EGFR revealed thatthis gene was not amplified. Similar to other patients with PGNTs, the patient in the present case fared well. From a genetic point of view the data in the present case are in accordance with previous findings of EGFR amplifications as uncommonin low-grade gliomas and gangliogliomas. Recurrent rearrangements of chromosome 7 have been noted in other mixed glioneuronal tumors. The data in this case suggest that genes located at chromosome 7 can also be involved in the pathogenesis of PGNT. In clinical terms it will be especially important to corroborate, through the analysis of further cases, the involvement of the chromosome 7p22 locus, a region where glial and neuronal linked genes (RAC1 and NXPH1) are known to be located.

PURPOSE: We previously showed that overexpression of epidermal growth factor receptor (EGFR) is associated with malignant grade in childhood glioma. The objective of this study was to determine whether protein expression of EGFR or platelet-derived growth factor receptor (PDGFR) and their active signaling pathways are related to malignant histology, progression of disease, and worse survival. EXPERIMENTAL DESIGN: Tissue microarrays were prepared from untreated tumors from 85 new glioma patients [22 high-grade gliomas (HGG) and 63 low-gradegliomas (LGG)] diagnosed at this institution from 1989 to 2004. Immunohistochemistry was used to assess total expression of EGFR, PDGFR beta, and PTEN and expression of phosphorylated EGFR, phosphorylated PDGFR alpha (p-PDGFR alpha), phosphorylated AKT, phosphorylated mitogen-activated protein kinase, andphosphorylated mammalian target of rapamycin. These results were correlated withclinicopathologic data, including extent of initial tumor resection, evidence ofdissemination, tumor grade, proliferation index, and survival, as well as with Affymetrix gene expression profiles previously obtained from a subset of these tumors. RESULTS: High expression of p-PDGFR alpha, EGFR, PDGFR beta, and phosphorylated EGFR was seen in 85.7%, 80.0%, 78.9%, and 47.4% of HGG and 40.0%,87.1%, 41.7%, and 30.6% of LGG, respectively. However, high expression of p-PDGFR alpha and PDGFR beta was the only significant association with malignant histology (P = 0.031 and 0.005, respectively); only the loss of PTEN expression was associated with worse overall survival. None of these targets, either alone or in combination, was significantly associated with progression-free survival in either LGG or HGG. CONCLUSIONS: High PDGFR protein expression is significantly associated with malignant histology in pediatric gliomas, but it does not represent an independent prognostic factor. Deficient PTEN expression is associated with worse overall survival in HGG.

Glioblastoma multiforme (GBM) occurs rarely in children. Relatively few studies have been performed on molecular properties of pediatric GBMs. Our objective in this study was to evaluate the genetic alterations in pediatric GBM (age < or = 18 years) with special reference to p53, p16, and p27 protein expression, alterations of the epidermal growth factor receptor (EGFR), and deletion of the phosphate and tensin homolog gene (PTEN). Thirty cases of childhood GBMs reported between January 2002 and June 2007 were selected, and slides stained with hematoxylin and eosin were reviewed. Immunohistochemical staining was performed for EGFR, p53, p16, and p27, and tumor proliferation was assessed by calculatingthe MIB-1 labeling index (LI). Fluorescence in situ hybridization analysis was performed to evaluate for EGFR amplification and PTEN deletion. Histopathological features and MIB-1 LI were similar to adult GBMs. p53 protein expression was observed in 63%. Although EGFR protein overexpression was noted in 23% of cases,corresponding amplification of the EGFR gene was rare (5.5%). Deletion of the PTEN gene was also equally rare (5.5%). One case showed polysomy (chromosomal gains) of chromosomes 7 and 10. Loss of p16 and p27 immunoexpression was observed in 68% and 54% of cases, respectively. In pediatric de novo/primary GBMs, deletion of PTEN and EGFR amplification are rare, while p53 alterations are morefrequent compared to primary adult GBMs. Frequency of loss of p16 and p27 immunoexpression is similar to their adult counterparts. This suggests that pediatric malignant gliomas are distinctly different from adult GBMs, highlighting the need for identification of molecular targets that may be adopted for future novel therapeutic strategies.

PURPOSE: The aim of this study was to perform a detailed cytogenetic and molecular genetic analysis of a tumor taken from a 14.5-year-old boy with glioblastoma multiforme who showed an atypical clinical course. METHODS: Formalin-fixed, paraffin embedded tumor tissue and the corresponding HGG-02 cellline derived from this tumor were analyzed using fluorescence in situ hybridization (FISH), G-banding, multiplex ligation-dependent probe amplification (MLPA), functional analysis of separated alleles in yeast (FASAY), immunohistochemistry (IHC), and immunocytochemistry (ICC). RESULTS: mutation of the p53 gene and hypermethylation of the MLH1 gene were detected by FASAY and MLPA, respectively. Cytogenetic analysis showed a polyploid karyotype with extensive heterogeneity in chromosome number. Using FISH, we identified a very unusual genetic change - a loss of EGFR gene copy in both the tumor tissue and the HGG-02 cell line. In accordance with the cytogenetic findings, IHC and ICC did not demonstrate overexpression of EGFR in the tumor tissue or HGG-02 cells. CONCLUSIONS: Despite his very poor prognosis, the patient experienced 34 months of event-free survival after surgery and adjuvant radiotherapy and chemotherapy.The detected loss of the EGFR gene copy may contribute to the unusual biologicalfeatures of this tumor, but the forthcoming detailed expression analysis of cancer regulatory pathways is necessary to better understand this tumor phenotype.

Rhabdomyosarcoma is an aggressive childhood malignancy, accounting for more than50% of ALL soft-tissue sarcomas in children. Even with extensive therapy, the survival rate among alveolar rhabdomyosarcoma patients with advanced disease is only 20%. The receptor tyrosine kinase Epidermal Growth Factor Receptor (EGFR) has been found to be expressed and activated in human rhabdomyosarcomas. In thisstudy we have used a genetically engineered mouse model for alveolar rhabdomyosarcoma (ARMS) which faithfully recapitulates the human disease by activating the pathognomic Pax3:Fkhr fusion gene and inactivating p53 in the maturing myoblasts. We have demonstrated that tumors from our mouse model of alveolar rhabdomyosarcoma express EGFR at both the mRNA and protein levels. We then tested the EGFR inhibitor, Erlotinib, for its efficacy in this mouse model of alveolar rhabdomyosarcoma. Surprisingly, Erlotinib had no effect on tumor progression, yet mice treated with Erlotinib showed 10-20% loss of body weight. These results suggest that EGFR might not be an a priori monotherapy target in alveolar rhabdomyosarcoma.

In February 2010, the Medical Advisory Secretariat (MAS) began work on evidence-based reviews of the literature surrounding three pharmacogenomic tests. This project came about when cancer Care Ontario (CCO) asked MAS to provide evidence-based analyses on the effectiveness and cost-effectiveness of three oncology pharmacogenomic tests currently in use in Ontario.Evidence-based analyses have been prepared for each of these technologies. These have been completed in conjunction with internal and external stakeholders, including a Provincial Expert Panel on Pharmacogenomics (PEPP). Within the PEPP, subgroup committees were developed for each disease area. For each technology, an economic analysis was also completed by the Toronto Health Economics and Technology Assessment Collaborative (THETA) and is summarized within the reports.THE FOLLOWING REPORTS CAN BE PUBLICLY ACCESSED AT THE MAS WEBSITE AT: www.health.gov.on.ca/mas or at www.health.gov.on.ca/english/providers/program/mas/mas_about.htmlGENE expressionPROFILING FOR GUIDING ADJUVANT CHEMOTHERAPY DECISIONS IN WOMEN WITH EARLY BREASTcancer: An Evidence-Based and Economic AnalysisEpidermal Growth Factor Receptor mutation (EGFR) Testing for Prediction of Response to EGFR-Targeting Tyrosine Kinase Inhibitor (TKI) Drugs in Patients with Advanced Non-Small-Cell Lung cancer: an Evidence-Based and Economic AnalysisK-RAS testing in Treatment Decisions for Advanced Colorectal cancer: an Evidence-Based and Economic Analysis. OBJECTIVE: The objective of this systematic review is to determine thepredictive value of KRAS testing in the treatment of metastatic colorectal cancer (mCRC) with two anti-EGFR agents, cetuximab and panitumumab. Economic analyses are also being conducted to evaluate the cost-effectiveness of KRAS testing. CLINICAL NEED: CONDITION AND TARGET POPULATION Metastatic colorectal cancer (mCRC) is usually defined as stage IV disease according to the American Joint Committee on cancer tumour node metastasis (TNM) system or stage D in the Duke'sclassification system. Patients with advanced colorectal cancer (mCRC) either present with metastatic disease or develop it through disease progression. KRAS (Kristen-RAS, a member of the rat sarcoma virus (ras) gene family of oncogenes) is frequently mutated in epithelial cancers such as colorectal cancer, with mutations occurring in mutational hotspots (codons 12 and 13) of the KRAS protein. Involved in EGFR-mediated signalling of cellular processes such as cellproliferation, resistance to apoptosis, enhanced cell motility and neoangiogenesis, a mutation in the KRAS gene is believed to be involved in cancer pathogenesis. Such a mutation is also hypothesized to be involved in resistance to targeted anti-EGFR (epidermal growth factor receptor with tyrosine kinase activity) treatments such as cetuximab and panitumumab, hence, the important in evaluating the evidence on the predictive value of KRAS testing in this context.KRAS mutation TESTING IN ADVANCED COLORECTAL cancer: Both cetuximab and panitumumab are indicated by Health Canada in the treatment of patients with metastatic colorectal cancer whose tumours are WT for the KRAS gene. Cetuximab may be offered as monotherapy in patients intolerant to irinotecan-based chemotherapy or in patients who have failed both irinotecan and oxaliplatin-based regimens and who received a fluoropyrimidine. It can also be administered in combination with irinotecan in patients refractory to other irinotecan-based chemotherapy regimens. Panitumumab is only indicated as a single agent after failure of fluoropyrimidine-, oxaliplatin-, and irinotecan-containing chemotherapy regimens. In Ontario, patients with advanced colorectal cancer who are refractory to chemotherapy may be offered the targeted anti-EGFR treatments cetuximab or panitumumab. Eligibility for these treatments is based on the KRAS status of their tumour, derived from tissue collected from surgical or biopsy specimens. It is believed that KRAS status is not affected by treatments, therefore, for patients for whom surgical tissue is available for KRAS testing, additional biopsies prior to treatment with these targeted agents is not necessary. For patients that have not undergone surgery or for whom surgical tissue is not available, a biopsy of either the primary or metastatic site is required to determine their KRAS status. This is possible as status at the metastatic and primary tumour sites is considered to be similar. RESEARCH QUESTION: To determine if there is predictive value of KRAS testing in guiding treatment decisions with anti-EGFR targeted therapies in advanced colorectal cancer patients refractory to chemotherapy. RESEARCH METHODS: LITERATURE SEARCH:The Medical Advisory Secretariat followed its standard procedures and on May 18,2010, searched the following electronic databases: Ovid MEDLINE, EMBASE, Ovid MEDLINE In-Process & Other Non-Indexed Citations, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews and The InternationalNetwork of Agencies for Health Technology Assessment database. The subject headings and keywords searched included colorectal cancer, cetuximab, panitumumab, and KRAS testing. The search was further restricted to English-language articles published between January 1, 2009 and May 18, 2010 resulting in 1335 articles for review. Excluded were case reports, comments, editorials, nonsystematic reviews, and letters. Studies published from January 1, 2005 to December 31, 2008 were identified in a health technology assessment conducted by the Agency for Healthcare Research and Quality (AHRQ), published in2010. In total, 14 observational studies were identified for inclusion in this EBA: 4 for cetuximab monotherapy, 7 for the cetuximab-irinotecan combination therapy, and 3 to be included in the review for panitumumab monotherapy INCLUSION CRITERIA: English-language articles, and English or French-language HTAs published from January 2005 to May 2010, inclusive.Randomized controlled trials (RCTs) or observational studies, including single arm treatment studies that include KRAS testing.Studies with data on main outcomes of interest, overall andprogression-free survival.Studies of third line treatment with cetuximab or panitumumab in patients with advanced colorectal cancer refractory to chemotherapy.For the cetuximab-irinotecan evaluation, studies in which at least 70% of patients in the study received this combination therapy. EXCLUSION CRITERIA: Studies whose entire sample was included in subsequent publications which have been included in this EBA.Studies in pediatric populations.Case reports, comments, editorials, or letters. OUTCOMES OF INTEREST: Overall survival (OS), medianProgression-free-survival (PFS), median.Response rates.Adverse eventrates.Quality of life (QOL). SUMMARY OF FINDINGS OF SYSTEMATIC REVIEW: CETUXIMABOR PANITUMUMAB MONOTHERAPY: Based on moderate GRADE observational evidence, there is improvement in PFS and OS favouring patients without the KRAS mutation (KRAS wildtype, or KRAS WT) compared to those with the mutation. CETUXIMAB-IRINOTECAN COMBINATION THERAPY: There is low GRADE evidence that testing for KRAS may optimize survival benefits in patients without the KRAS mutation (KRAS wildtype,or KRAS WT) compared to those with the mutation. However, cetuximab-irinotecan combination treatments based on KRAS status discount any effect of cetuximab in possibly reversing resistance to irinotecan in patients with the mutation, as observed effects were lower than for patients without the mutation. Clinical experts have raised concerns about the biological plausibility of this observation and this conclusion would, therefore, be regarded as hypothesis generating. ECONOMIC ANALYSIS: Cost-effectiveness and budget impact analyses were conducted incorporating estimates of effectiveness from this systematic review. Evaluation of relative cost-effectiveness, based on a decision-analytic cost-utility analysis, assessed testing for KRAS genetic mutations versus no testing in the context of treatment with cetuximab monotherapy, panitumumab monotherapy, cetuximab in combination with irinotecan, and best supportive care.Of importance to note is that the cost-effectiveness analysis focused on the impact of testing for KRAS mutations compared to no testing in the context of different treatment options, and does not assess the cost-effectiveness of the drug treatments alone. CONCLUSIONS: KRAS status is predictive of outcomes in cetuximab and panitumumab monotherapy, and in cetuximab-irinotecan combination therapy. While KRAS testing is cost-effective for ALL strategies considered, it is not equally cost-effective for ALL treatment options.#CN- Health Quality Ontario

Objectives: The bevacizumab/erlotinib combination was reported with high clinical activity for advanced hepatocellular carcinoma (HCC) by a phase II study conducted in the USA. This multicenter study across several Asian countries was to evaluate the safety and efficacy of the combination in this population. Methods: Patients with histology-proven HCC, advanced disease and child-Pugh class A liver function received bevacizumab 5 mg/kg intravenously every 2 weeks and erlotinib 150 mg/day orally as first-line therapy. The primary end point wasprogression-free survival at 16 weeks (PFS-16W). The expression of epidermal growth factor receptor (EGFR), phospho-AKT and vascular endothelial growth factor, the microvessel density and the EGFR gene copy number in HCC tissues were correlated with treatment efficacy. Results: Fifty-one patients were enrolled. The PFS-16W was 35.3% (95% CI 22.4-49.9), the median PFS was 2.9 months (95% CI,1.3-4.4) and the median overall survival was 10.7 months (95% CI, 6.2-15.2). Grade 3/4 toxicities were uncommon, including rash, acne (10% each), diarrhea (6%) and gastrointestinal bleeding (4%). None of the evaluated biomarkers correlated with disease control or PFS. Conclusions: Bevacizumab plus erlotinib showed good tolerability and modest activity in this Asian cohort. Further studies are warranted to identify the predictive biomarkers of this combination.#CI- Copyright (c) 2013 S. Karger AG, Basel.

Brain stem gliomas are pediatric astrocytomas that histologically resemble adultsupratentorial astrocytomas such as glioblastomas multiforme (GBM). Our molecular genetic studies have suggested that adult GBM can be divided into two genetic subsets: tumors with p53 tumor suppressor gene mutations and chromosome 17p lossthat occur more commonly in younger patients; and tumors with epidermal growth factor receptor (EGFR) gene amplification that occur more commonly in older patients. Brain stem gliomas have not been studied since biopsies of these tumors are rare and extremely small. We investigated the molecular genetic composition of seven brain stem glioblastomas (two small biopsies, five autopsies) using polymerase chain reaction (PCR) assays for chromosomal loss, gene mutation and gene amplification. Four cases lost portions of chromosome 17p that included thep53 gene. These four cases and one additional case had mutations in the p53 gene. None of the cases showed amplification of the EGFR gene. Allelic losses of the long arm of chromosome 10 were noted in four cases. These results suggest similarities between pediatric brain stem glioblastomas and those GBM that occurin younger adult patients, and confirm the utility of PCR-based means of studying small and archival brain tumor specimens.

cancer has been defined as a fundamental disorder of cellular growth control. Which arises in some cells through changes in genes (DNA-level: geneamplification, mutation and rearrangement) or their expression (RNA- and protein-level), and gives these cells a growth advantage in comparison to the surrounding cells. Since the last decade we know the identity of these genes andthe nature of the changes they underwent in the cancer cell. Only a few of the known oncogenes play a role in head and neck cancer. These are the EGFR (epidermal growth factor receptor), c-myc, the ras gene family, int-2, hst- 1 and bcl- 1. In some clinical disorders, like childhood neuroblastoma and breast cancer, oncogenes play already an important role in tumor staging as well as a prognostic parameter. The aim for the future is the therapeutic application of oncogenes better known as gene therapy.

Glioblastoma multiforme is a rare neoplasm in children and is often located infratentorially, particularly in the brainstem: pediatric glioblastomas arise frequently (here 60%) outside the cerebral hemispheres. We investigated 20 pediatric glioblastomas for mutational inactivation of the p53 tumor suppressor gene, loss of p16 protein expression and overexpression of the epidermal growth factor receptor (EGFR). mutations in the p53 gene were identified in 5/20 (25%) glioblastomas, 4 of which occurred in primary glioblastomas with a clinical history of less than 4 months and neither clinical nor histologic evidence of a less malignant precursor lesion. Loss of p16 expression was detected in 11/18 (61%) glioblastomas. Overexpression of the EGFR was infrequent (2/19, 11%) and included 1 tumor with a p53 mutation. Of 4 secondary glioblastomas that progressed from histologically diagnosed lower grade tumors, one contained a p53mutation. Our results are at variance with similar studies in adult patients in which primary and secondary glioblastomas are characterized by EGFR overexpression and p53 mutations, respectively, suggesting that the evolution ofpediatric glioblastomas follows different genetic pathways.

Recent in vitro studies of the epidermal growth factor receptor (EGFR) family have revealed complex signaling interactions involving the production of ligand-mediated heterodimers synergistic for the transformation of cells in vitro. In a series of 70 patients with childhood medulloblastoma, we have used immunohistochemistry and Western blotting analysis to investigate the expressionpatterns of ALL four EGFR family members (EGFR, HER2, HER3, and HER4) and heregulin-alpha, a ligand for the HER3 and HER4 receptors. The majority of casesexpressed two or more receptor proteins; coexpression of the HER2 and HER4 receptors occurred in 54%. expression of the ligand heregulin-alpha was detectedin 31% of tumors. To investigate whether coexpression results in receptor heterodimerization, we have also performed immunoprecipitation analysis of protein extracts from primary tumors, and we demonstrate various patterns of receptor interaction including between HER2 and HER4. In multivariate 25-year survival analysis with clinicopathological disease features, no individual receptor or heregulin-alpha achieved significance. In contrast, when considered together in the multivariate model, coexpression of HER2 and HER4 demonstrated independent prognostic significance (P = 0.006). These data suggest the hypothesis that HER2-HER4 receptor heterodimerization is of particular biological significance in this disease, and this report is the first to demonstrate potential clinical significance of EGFR family heterodimerization in human cancer. Finally, we have also analyzed expression of the AP-2 transcription factor implicated in the positive regulation of HER2 and HER3 gene transcriptionin malignant cells and reveal an association between AP-2 expression and not only HER2 and HER3, but also HER4 levels in medulloblastoma primary tumors.

PURPOSE: pediatric central nervous system (CNS) tumors comprise a wide variety of histologic subtypes ranging from the benign juvenile pilocytic astrocytoma to the highly aggressive atypical teratoid/rhabdoid tumor. Although some brain tumors are seen in association with inherited genetic disorders which predispose to malignancies, most are sporadic. Current knowledge regarding the cytogenetic andmolecular genetic events which have been implicated in the development or progression of common brain tumors in children in the subject of this review. METHODS: Combined cytogenetic and molecular genetic approaches, including fluorescence in situ hybridization, have been used to identify genomic alterations in different histologic types of pediatric brain tumors. RESULTS: The most frequent abnormality in primitive neuroectodermal tumor/medulloblastoma is an i(17q), present in approximately 50% of cases. This finding implicates the presence of a tumor suppressor gene on 17p, which is important in tumor development. A number of genes on 17p have been eliminated as candidates for this locus, including TP53. A tumor suppressor gene in chromosome band 22q11.2 has been hypothesized to play a role in atypical teratoid/rhabdoid tumors, and positional cloning strategies are in progress to identify a rhabdoid tumor gene.Chromosome 22 deletions are also seen in meningiomas and a small percentage of ependymomas, but it is not yet known whether the same gene is responsible for more than one malignancy. With regard to childhood astrocytomas, tumor-associated genetic changes have not yet been identified for the common juvenile pilocytic or low grade diffuse astrocytoma. In contrast, malignant anaplastic astrocytomas and glioblastoma multiforme have abnormalities similar to those seen in adults, including loss of alleles on 17p13 and TP53 mutations, trisomy 7, EGFR rearrangements, and loss of chromosomes 10 and 22. CONCLUSIONS: The presence of tumor-associated genetic abnormalities has clinical utility in a differential diagnostic setting, and has lead to the identification of genes which contributeto tumorigenesis.