Pediatric glial tumors

Opinion statement Glial neoplasms in children comprise many heterogeneous tumors that include pilocytic and fibrillary astrocytomas, ependymomas, and the diffuse intrinsic pontine gliomas. In contrast to adults, most of whom present with high-grade fibrillary neoplasms, alternate histologies represent most cases seen in the pediatric setting. In addition, although most adult gliomas are supratentorial in location, in pediatrics infratentorial tumors (posterior fossa and brain stem) predominate. We discuss three specific tumors: diffuse intrinsic pontine gliomas; pilocytic astrocytomas; and ependymomas. Maximal surgical resection is the mainstay of therapy for both pilocytic astrocytomas and ependymomas. Failure to achieve an optimal resection often results in progression and the need for further therapy for patients with pilocytic astrocytomas, and is ultimately fatal in most children with subtotally resected ependymomas. Surgical resection has no role in the treatment of pontine gliomas. Focal radiation therapy is included routinely in the treatment of ependymomas, and it has been shown to improve event-free survival. This therapy also is used in the treatment of pontine gliomas because radiation treatment appears to slow inevitable tumor progression. Radiation therapy in pilocytic astrocytomas is generally reserved for patients who progress after an initial surgical resection or for those patients with midline tumors; these patients are poor candidates for aggressive surgical resection. The role of chemotherapy in these tumors is in evolution. Chemotherapy for pilocytic astrocytomas, particularly in young children (for whom radiation therapy is avoided), appears to be effective in the treatment of a subset of patients. Up-front chemotherapy is generally reserved for the youngest children who present with ependymoma. In the recurrence setting, chemotherapy has shown some activity, although this approach is never curative. Despite the application of various chemotherapeutics and other biologic agents, none of these therapies has improved the prognosis for patients with the uniformly lethal pontine glioma.     

Molecular biology of malignant gliomas

Gliomas are the most common primary brain tumours. In keeping with the degree of aggressiveness, gliomas are divided into four grades, with different biological behaviour. Furthermore, as different gliomas share a predominant histological appearance, the final classification includes both, histological features and degree of malignancy. For example, gliomas of astrocytic origin (astrocytomas) are classified into pilocytic astrocytoma (grade I), astrocytoma (grade II), anaplastic astrocytoma (grade III) and glioblastoma multiforme (GMB) (grade IV). Tumors derived from oligodendrocytes include grade II (oligodendrogliomas) and grade III neoplasms (oligoastrocytoma). Each subtype has a specific prognosis that dictates the clinical management. In this regard, a patient diagnosed with an oligodendroglioma totally removed has 10–15 years of potential survival. On the opposite site, patients carrying a glioblastoma multiforme usually die within the first year after the diagnosis is made (table 1). Therefore, different approaches are needed in each case. Obviously, prognosis and biological behaviour of malignant gliomas are closely related and supported by the different molecular background that possesses each type of glioma. Furthermore, the ability that allows several low-grade gliomas to progress into more aggressive tumors has allowed cancer researchers to elucidate several pathways implicated in molecular biology of these devastating tumors. In this review, we describe classical pathways involved in human malignant gliomas with special focus with recent advances, such as glioma stem-like cells and expression patterns from microarray studies. Supported by an unrestricted educational grant by Bristol-Myers Squibb.     

Tumor antigen precursor protein profiles of adult and pediatric brain tumors identify potential targets for immunotherapy

Objectives We evaluated and compared tumor antigen precursor protein (TAPP) profiles in adult and pediatric brain tumors of 31 genes related to tumor associated antigens (TAA) for possible use in immunotherapy. Antigens were selected based on their potential to stimulate T cell responses against tumors of neuroectodermal origin. Methods Thirty-seven brain tumor specimens from 11 adult and 26 pediatric patients were analyzed by quantitative real-time PCR for the relative expression of 31 TAPP mRNAs. The age range of adults (4F:7M) was 27–77 years (median 51.5 ± 14.5 years) and for pediatrics (12F:14M) was 0.9–19 years (median 8.3 ± 5.5 years). Histological diagnoses consisted of 16 glioblastomas, 4 low grade astrocytomas, 10 juvenile pilocytic astrocytomas, and 7 ependymomas. Results The adult gliomas expressed 94% (29 of 31) of the TAPP mRNAs evaluated compared with pediatric brain tumors that expressed 55–74% of the TAPP mRNAs, dependent on tumor histological subtype. Four types of TAPP expression patterns were observed: (1) equal expression among adult and pediatric cases, (2) greater expression in adult than pediatric cases, (3) expression restricted to adult GBM and (4) a random distribution. The pediatric brain tumors lacked expression of some genes associated with engendering tumor survival, such as hTert and Survivin. Conclusions The potential TAA targets identified from the TAPP profiles of 31 genes associated with adult and pediatric brain tumors may help investigators select specific target antigens for developing dendritic cell- or peptide-based vaccines or T cell-based immunotherapeutic approaches against brain tumors. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Elizabeth W. Newcomb and Martin R. Jadus contributed equally as senior authors.     

Molecular pathogenesis of pediatric astrocytic tumors

Astrocytomas are the most common pediatric brain tumors, accounting for 7%-8% of all childhood cancers. Relatively few studies have been performed on their molecular properties; therefore, classification of pediatric astrocytic tumors into genetic subtypes similar to that of adult tumors remains to be defined. Here, we report an extensive characterization of 44 pediatric astrocytomas--16 diffuse astrocytomas (WHO grade II), 10 anaplastic astrocytomas (WHO grade III), and 18 glioblastomas (WHO grade IV)--in terms of genetic alterations frequently observed in adult astrocytomas. Some form of p53 mutation was found in three diffuse astrocytomas, in three anaplastic astrocytomas, and in six glioblastomas examined; PTEN mutations were detected only in two glioblastomas. EGFR amplification was detected in only one anaplastic astrocytoma and two glioblastomas, but no amplification was observed for the PDGFR-alpha gene. Loss of heterozygosity (LOH) on 1p/19q and 10p/10q was less common in pediatric astrocytic tumors than in those seen in adults, but the frequency of LOH on 22q was comparable, occurring in 44% of diffuse astrocytomas, 40% of anaplastic astrocytomas, and 61% of glioblastomas. Interestingly, a higher frequency of p53 mutations and LOH on 19q and 22q in tumors from children six or more years of age at diagnosis was found, compared with those from younger children. Our results suggest some differences in children compared to adults in the genetic pathways leading to the formation of de novo astrocytic tumors. In addition, this study suggests potentially distinct developmental pathways in younger versus older children.     

Vascular Endothelial Growth Factor (VEGF) in Astrocytic Gliomas – A Prognostic Factor?

Survival in astrocytic gliomas is closely related to WHO tumor grade. Within one tumor grade, especially in grade II and III tumors, the clinical course is variable and can hardly be predicted by histological criteria. Neovascularization is a neuropathological hallmark in high grade gliomas and angiogenic factors may play an important role in malignant tumor progression. Therefore, 162 primary astrocytic gliomas (57 astrocytomas WHO grade II, 27 astrocytomas WHO grade III and 78 glioblastomas WHO grade IV) were investigated immunohistochemically for expression of vascular endothelial growth factor (VEGF), which is considered to represent the main angiogenic factor in astrocytic gliomas. Clinical data known to influence prognosis were documented. VEGF expression was found in 21 of 57 astrocytomas WHO grade II (36.8%), in 18 of 27 astrocytomas WHO grade III (66.7%) and in 50 of 78 glioblastomas (64.1%). A strong correlation between VEGF expression and survival was found within the whole study group, however, within one tumor grade no such correlation was obvious. In a multifactorial analysis VEGF expression was not found to be an independent prognostic factor in astrocytic gliomas.     

Long-term molecular changes in WHO grade II astrocytomas following radiotherapy

Monitoring the long-term radiotherapy-associated molecular changes in low-grade gliomas(LGGs) facilitates the understanding of LGG response to radiotherapy.In this study,we used immunohistochemistry to analyze the expression of Ki-67,tumor protein P53(TP53),P21,and P27 in 8 paired WHO grade II astrocytoma samples.The interval between radiotherapy(RT) and the second surgery was more than 3 months in all cases.The average Ki-67 labeling index(LI) was 5.3% in pre-RT samples and 11.54% in post-RT samples.Ki-67 LI was higher in the primary tumors that underwent malignant transformation observed at the second surgery after radiation.Post-RT Ki-67 LI decreased in 2 cases with an interval of less than 12 months between RT and the second surgery.TP53 expression was found in 3 out of 4 pre-RT samples with malignant transformation and in 1 out of 4 pre-RT samples without malignant transformation.Post-RT TP53 increased in 2 cases in which increased expression of P21 or P27 was also observed.Our study suggests that radiotherapy can inhibit WHO grade II astrocytoma proliferation as reflected by Ki-67 LI,but the effect attenuates with time.In addition,there is a tendency of malignant transformation for WHO grade II astrocytomas with a high Ki-67 level or TP53 expression in initial samples.     

Histological classification of human gliomas: state of art and controversies

The histological classification of human gliomas remains in 2005 a challenge. The aim is to define the histological type of glioma (astrocytic, oligodendrocytic or mixed) and the grade in order to classify the patients and give them an accurate treatment. Although the standard remains the WHO classification, this classification suffered from lack of reproducibility among pathologists. In particular this classification does not take into account the intrinsic morphological heterogeneity of infiltrative gliomas and does not discriminate the tumour cells from the residual brain parenchyma. According to the WHO classification, infiltrative gliomas encompass astrocytic gliomas (diffuse astrocytomas grade II, anaplastic astrocytomas grade III and glioblastomas grade IV), oligodendroglial tumours (oligodendrogliomas grade II, anaplastic oligodendrogliomas grade III) and mixed gliomas (oligoastrocytomas grade II and anaplastic oligoastrocytomas grade III). Circumscribed gliomas mainly corresponds to pilocytic astrocytomas (grade I). In contrast, the Sainte Anne classification takes into account the macroscopic informations provided by imaging techniques and the tumour growth patterns. Three distinct tumour growth patterns may be seen in gliomas, type I: tumor tissue only, type II: tumour tissue and isolated tumor cells permeating the brain parenchyma (ITC) and type III: ITCs only and no tumor tissue. According to the Sainte Anne classification, gliomas are divided into astrocytic gliomas (pilocytic astrocytomas, structure type I, glioblastomas structure type II) and oligodendrogliomas and mixed oligoastrocytomas (grade A: lack of contrast enhancement and lack of endothelial hyperplasia, structure type III; and grade B: contrast enhancement or endothelial hyperplasia, structure type II and III). In the future the glioma classification has to be unique and should take into account clinical data, neuroradiological and histological features and results of molecular biology.     

The clinical value of Ki-67/MIB-1 labeling index in human astrocytomas

The current WHO classification of human astrocytomas has limitations in predicting prognosis and diagnosis, and there is a need for additional factors. Several studies have investigated the clinical value of proliferative activity in these tumors, especially the Ki-67/MIB-1 labeling index (LI). The aim of this study was to review the literature on this topic to get a survey of the current experience. All studies show increasing values of Ki-67/MIB-1 LI with increasing grade of malignancy. Most of them demonstrate that MIB-1 LI differentiates well between diffuse astrocytomas WHO grade II (AII) and anaplastic astrocytomas (AA) and between AII and glioblastomas (GM), but not between AA and GM. There is, however, considerable overlap of indices between the different malignancy groups. Further, in most studies positive correlations between MIB-1 LI and survival are found, though the proposed cut-off values vary substantially between the reports. The studies reviewed report MIB-1 LI as an important prognostic factor in human astrocytomas. Due to the great spread of values between the various tumor grades, however, MIB-1 LI cannot be used as a diagnostic factor alone but should be used in combination with established criteria of histological malignancy. It may be especially useful in cases where histology reveals a low-grade astrocytoma whereas other parameters indicate a more malignant neoplasm. Thus, it is our opinion that MIB-1 LI should be a part of the routine investigation in patients with astrocytic tumors. Until larger multicenter studies based on standardized immunohistopathological procedures have been completed, each laboratory has to establish its own practice. (Pathology Oncology Research Vol 12, No 3, 143–147)     

Atypical and anaplastic meningiomas treated with bevacizumab

Pilocytic astrocytoma is a WHO grade 1 brain tumor common in children. Relatively little is known about the behavior of pilocytic astrocytomas in adult patients, largely due to the rarity of pilocytic astrocytoma in this population. Some data suggest that adults share the excellent prognosis seen in children, while other reports suggest more aggressive tumor behavior in adult patients. Patients diagnosed with pilocytic astrocytoma between 1973 and 2008 were identified in the National Cancer Institute Surveillance, Epidemiology, and End Results Program database. Age-group specific survival was analyzed with overall, expected, and cancer-specific survival rates. Further survival analyses were performed with the Kaplan–Meier method and Cox Proportional Hazards models. 3,066 patients with pilocytic astrocytoma were identified, including 865 patients aged 20 years and older. Survival rates declined significantly with age, from 96.5% 60-month survival in patients 5–19 years (95% CI 95.3–97.4) to 52.9% 60-month survival in adult patients 60+ years of age (95% CI 38.4–65.5), with a corresponding decrease in relative and cancer-specific survival rates. Gross total resection was a positive prognostic indicator in adults, while patients receiving radiation had shorter survival regardless of extent of resection. Pilocytic astrocytoma is associated with higher mortality in adult patients than in children and teens, and survival decreases with increasing age in adults. The morbidity of pilocytic astrocytoma in adults provides rationale for future trials of adjuvant treatment in high-risk patients.     

The Role of Immunohistochemistry in Predicting Behavior of Astrocytic Tumors

The purpose of this study was to analyze the significance of p53, bcl-2 and EGFR expression in the grading and biological behavior of astrocytic tumors, especially in the Indian population. A total of 117 cases of astrocytomas graded using the WHO grading system published in 2007 were immunolabeled using p53, EGFR and bcl-2 monoclonal antibodies and analyzed with respect to grade and other relevant parameters. The 117 cases included 16 cases of pilocytic astrocytomas and 25, 15 and 61 cases of diffuse fibrillary astrocytomas WHO grade II, anaplastic astrocytomas WHO grade III and glioblastomas (GBM), respectively. Our results showed that p53 alterations is an early event in astrocytic gliomagenesis, but is not significant in the evolution of pilocytic astrocytomas. Bcl-2 expression did not correlate with grade and no statistical correlation was seen with p53 expression. EGFR protein expression correlated with the severity of tumor grade. Of the GBM cases, 47.5% were p53 positive only, 18% were EGFR positive only, 16.5% were negative for both and 18% were positive for both. The mean age in the dual positive category was significantly higher when compared to the others. EGFR and p53 alterations are not mutually exclusive and mightn act synergistically to promote progression. We also noted a significantly higher p53 expression in females in GBMs. Though most of our findings correlated with those of previous studies, some differences were noted, especially in the pattern of immunoexpression in GBMs, perhaps because of ethnicity.     

A histopathological diagnostic marker for human spinal astrocytoma: expression of glial fibrillary acidic protein-δ

Although histopathological diagnosis of spinal cord astrocytomas is important for postoperative treatment planning and prognosis, there is a lack of reliable immunohistochemical markers. The purpose of our study was to assess the expression pattern of GFAP-δ in spinal cord astrocytomas in human patients and to evaluate the utility of GFAP-δ as an immunohistochemical diagnostic marker. A total of 22 patients with spinal cord astrocytic tumors were included in this study. Patients were classified according to the WHO designation of human astrocytic tumors; three patients had grade 1 astrocytomas, 14 had grade 2, and five had Grade 3. Normal control spinal cord tissues were obtained at autopsy from the cervical spinal cords of ten patients with no history of cervical trauma or neurological disease. We evaluated BRAF, IDH1, GFAP, and GFAP-δ immunoreactivity in control tissues and astrocytomas. In normal control tissues, GFAP immunoreactivity was detected in astrocytes whereas GFAP-δ immunoreactivity was observed in very few astrocytes adjacent to the subpial layer of the spinal cord. GFAP-δ immunoreactivity was significantly correlated with spinal cord astrocytoma grade in astrocytomas compared to that in normal control tissues. The optical density of GFAP-δ increased significantly with astrocytoma grade (correlation coefficient, R ² = 0.680). Also, BRAF and IDH1 immunoreactivity were detected in astrocytoma. We suggest that GFAP-δ may be an additional, reliable histopathological diagnostic marker for spinal cord astrocytomas.     

Brainstem gliomas--a clinicopathological study of 45 cases with p53 immunohistochemistry

BACKGROUND: Brainstem tumors represent 10% of central nervous system tumors, accounting for 30% of pediatric posterior fossa tumors. AIMS: The aim of this study was to clinicopathologically correlate 45 cases of brain stem gliomas and determine the occurrence and prognostic significance of p53 expression. MATERIALS AND METHOD: 45 cases of brain stem gliomas encountered during a 19-year period. 30 were diagnosed by surgical biopsy and 15 at autopsy. In 25 cases p53 immunohistochemistry (Avidin Biotinylated technique) was performed. The WHO brain tumor classification and Stroink's CT classification were applied. STATISTICAL ANALYSIS USED: Chi square test. RESULTS AND CONCLUSIONS: 51 % of gliomas were observed in the first decade of life. The female to male ratio was 1.04: 1. The commonest presenting features were cranial nerve palsies (33%) and cerebellar signs (29.8%). 55.55% of cases were located in the pons, 31.01% in the medulla and 13.33% in the midbrain. Diffuse astrocytomas were seen in 40 cases (5% were Grade I, 47.5%Grade II, 32.5% Grade III and 15% Grade IV) and pilocytic astrocytomas in 5 cases. Grade IV patients had 2- 3 mitoses /10 high power fields and had a poorer survival rate. Grade II astrocytomas were treated with excision and radiotherapy, while grade III and IV tumors were treated with radiotherapy and chemotherapy (CCNU). Improvement was noted in 20% of patients postoperatively. The outcome was better in patients who were treated surgically. p53 is a frequently mutated gene in brain stem astrocytomas. It was found in 50 % of glioblastoma multiforme, 28.57% of grade III astrocytoma and 12.5% of grade II astrocytoma, while grade 1 astrocytomas failed to express p53 protein. p53 positivity was more in high grade lesions, decreasing significantly in lower grade lesions.     

A correlative study of gliomas usingIn vivo bromodeoxyuridine labeling index and computer-aided malignancy grading

An in vivo bromodeoxyuridine (BrdU) labeling index (LI) was estimated in 43 cases of astrocytic tumors and mixed gliomas by one hour intra-operative intravenous infusion at a dose of 200 mg/m2 and correlated with (a) histological grading using a computer aided malignancy classifier TESTAST-268; and (b) histological typing using WHO classification. The lowest BrdU LI was seen in pilocytic and gemistocytic astrocytomas followed by astrocytomas, anaplastic astrocytomas and glioblastoma multiforme in that order. Mixed oligoastrocytomas followed the pattern of their astrocytic counterparts. Tumors of similar histological type showed different BrdU LI values especially amongst astrocytomas and glioblastomas. A statistically significant difference in the BrdU LI was also noted between the higher TESTAST grades of astrocytomas (T III and IV) versus the lower TESTAST grades (T II). Unlike earlier reports in literature, in the present study the category of BrdU LI of <1 contained no case of anaplastic astrocytoma or glioblastoma multiforme (TESTAST grades III and IV). Likewise, the category of BrdU LI >5 contained only anaplastic astrocytoma and glioblastoma multiforme (TESTAST grades III and IV). Maximum spread of cases was seen in the BrdU LI category of 1-5, not only in terms of histological types but also TESTAST grades. Thus there appeared to be a positive trend of increasing BrdU LI values both with histological types and increasing TESTAST grades. Further, an interesting observation was that by using a combination of TESTAST grades and BrdU LI, the histologically homogenous glioblastoma group could be further subdivided into 4 categories which showed a trend towards prognostic correlation. Thus, this study though preliminary with number of cases being small in some groups, highlights the possible usefulness of combined histological typing, TESTAST grading and in vivo BrdU LI for prognostication of gliomas especially glioblastoma multiforme.     

The prostate stem cell antigen represents a novel glioma-associated antigen

Gliomas of WHO grades III-IV are malignant brain tumors mostly resistant to conventional therapies. Therefore, novel strategies for the treatment of gliomas are warranted. Although immunotherapy is gaining increased attention for the treatment of malignant gliomas and in particular of glioblastoma multiforme (GBM), this approach requires the identification of appropriate antigens. Our aim was to investigate the expression of the prostate stem cell antigen (PSCA), a highly N-glycosylated phosphatidylinositol (GPI)-anchored cell surface protein, in gliomas of different WHO grades in order to evaluate its potential as a diagnostic marker and as a target for immunotherapy. Tumor specimens and controls were assessed by quantitative RT-PCR, Western blotting and immunohistochemistry. The samples investigated in the study consisted of 210 human glial tumors, among which 31 were oligodendrogliomas, 9 ependymomas and 170 were astrocytomas (including 134 glioblastomas). PSCA was absent in normal brain tissue, but was detected in WHO grade III-IV gliomas. Weak PSCA protein expression was also recognized in some WHO grade I and WHO grade II tumors. The difference between WHO grade I-II tumors and WHO grade III-IV tumors was statistically significant (p<0.001). Our results suggest that increased PSCA expression levels are linked to gliomas of WHO grades III and IV, and may represent a suitable additional target for immunotherapy of gliomas.     

Immunohistochemical actinin-4 expression in infiltrating gliomas: association with WHO grade and differentiation

Actinin-4 is an isoform of nonmuscular α-actinin and actin-bundling protein that plays an important role in cancer invasion and metastasis by enhancing cellular motility. Recent studies have revealed an association between several clinicopathological profiles and actinin-4 overexpression in human cancers. In this study, we investigated the immunohistochemical actinin-4 expression in 39 infiltrating gliomas. The specimens included three diffuse astrocytomas, three oligodendrogliomas, one oligoastrocytoma, two anaplastic astrocytomas, four anaplastic oligodendrogliomas, three anaplastic oligoastrocytomas, 17 glioblastomas, four gliosarcomas, and two glioblastomas with oligodendroglial component. All seven World Health Organization (WHO) grade II tumors were negative for actinin-4, whereas 20 of 22 tumors with strong actinin-4 expression were WHO grade IV. Actinin-4 expression was significantly associated with histological grade (P < 0.0001) and proliferative activity measured by Ki-67 staining (P = 0.0045). Notably, actinin-4 expression was more pronounced in high-grade astrocytic tumors than oligodendroglial tumors (P < 0.0001). Additionally, pseudopalisading cells in glioblastoma exhibited stronger actinin-4 expression than the rest, likely reflecting enhanced cellular motility in pseudopalisades. This study is the first to demonstrate significant correlation between actinin-4 expression and tumor grade using clinical glioma samples. Although diagnostic utility of this marker awaits future exploration, actinin-4 may help distinguish between astrocytic and oligodendroglial lines of differentiation.     

Molecular biology of pediatric gliomas

The genes involved in the genesis and progression of adult astrocytic tumors have been an area of considerable investigation. The tumor suppressor gene, p53, has been implicated, as has the epidermal growth factor receptor gene. Additional currently unidentified genes lie on chromosomes 10 and 19. Interestingly, work on pediatric astrocytomas suggests that the genes involved are different. p53 is rarely mutated in pediatric tumors, the epidermal growth factor receptor gene is rarely amplified or mutated, and chromosome 10 deletions are rare. The only pediatric tumor that seems to mimic the findings in adult tumors is brainstem glioma, perhaps explaining the uniformly grim prognosis in this type of tumor. In the pilocytic astrocytoma of childhood, mutations in the neurofibromatosis type I gene have been implicated in tumor development. In this review, the oncogenesis of pediatric gliomas is discussed and compared and contrasted to what is known about tumors.