GFAP in brain tumor diagnosis: possibilities and limitations

The GFAP proteoform puzzle: How to advance GFAP as a fluid biomarker in neurological diseases

Glial fibrillary acidic protein (GFAP) is a well-established biomarker of reactive astrogliosis in the central nervous system because of its elevated levels following brain injury and various neurological disorders. The advent of ultra-sensitive methods for measuring low-abundant proteins has significantly enhanced our understanding of GFAP levels in the serum or plasma of patients with diverse neurological diseases. Clinical studies have demonstrated that GFAP holds promise both as a diagnostic and prognostic biomarker, including but not limited to individuals with Alzheimer's disease. GFAP exhibits diverse forms and structures, herein referred to as its proteoform complexity, encompassing conformational dynamics, isoforms and post-translational modifications (PTMs). In this review, we explore how the proteoform complexity of GFAP influences its detection, which may affect the differential diagnostic performance of GFAP in different biological fluids and can provide valuable insights into underlying biological processes. Additionally, proteoforms are often disease-specific, and our review provides suggestions and highlights areas to focus on for the development of new assays for measuring GFAP, including isoforms, PTMs, discharge mechanisms, breakdown products, higher-order species and interacting partners. By addressing the knowledge gaps highlighted in this review, we aim to support the clinical translation and interpretation of GFAP in both CSF and blood and the development of reliable, reproducible and specific prognostic and diagnostic tests. To enhance disease pathology comprehension and optimise GFAP as a biomarker, a thorough understanding of detected proteoforms in biofluids is essential.

Case report: Polymorphous low-grade neuroepithelial tumor of the young and supratentorial ependymoma diagnosed in an adult male

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a rare central nervous system (CNS) pathology predominantly observed in the pediatric population. Ependymomas also exhibit a peak incidence in early childhood, with rare presentations after early adulthood. In this report, we describe a rare case of a 41-year-old man diagnosed sequentially with a polymorphous low-grade neuroepithelial tumor of the young, followed by a supratentorial ependymoma within a year. He underwent tumor resection for both tumors, as well as adjuvant radiation therapy for the ependymoma. Despite these interventions, he ultimately succumbed to tumor progression and postoperative complications. Currently, no genetic syndromes are known to link these two primary CNS tumors. Two commonalities at the chromosomal and cellular level include histone gene H3F3A mutations and positive glial fibrillary acidic protein staining on immunohistochemistry. To the best of our knowledge, this unique dual pathology has not been previously described in the literature, making this case an avenue for further investigation and research into connections between these two distinct CNS pathologies.

Extracranial Glioblastoma Metastasis: A Neuropathological Case Report

Glioblastoma (GBM) is a central nervous system (CNS) high-grade glioma with a dismal patient prognosis. Classical concepts surrounding GBM development and progression indicate its ability to produce metastasis within the CNS, one of the few primary tumors with such capabilities. While classical concepts state that no primary CNS tumor produces extracranial metastasis, there have been multiple reports of such occurrences over the previous two decades. Here, we report a case of a male in his forties who presented to our institution with complaints of progressive headache and a history of right temporal craniotomy one month prior with a histologically verified GBM performed at another institution. Neuroradiology confirmed a residual tumor in the areas of the previous craniotomy, and gross total excision confirmed the diagnosis of GBM, although based on the presence of connective tissue amidst the tumor stroma, gliosarcoma could not be ruled out. The patient initiated treatment, and his condition remained stable for four calendar years until he again presented to our institution with a rapidly growing tumor mass in the right lateral neck region. Excision of the neck mass showed histopathological features of a tumor comprised of atypical cells with pronounced polymorphism, some with spindle cell morphology and a tendency for fascicular growth and focal palisade necrosis. Immunohistochemistry with a broad set of markers disproved epithelial, mesenchymal, melanocytic, and lymphoid genesis, with some markers of glial genesis present; hence, metastatic GBM was established. The patient reinitiated treatment and is currently stable. The steadily increasing amount of similar reported cases, together with the steady, albeit small, increase in GBM patient survival and improvement of neurooncological healthcare distribution and follow-up, challenge the classical concepts of GBM and other primary CNS tumors being unable to produce metastasis and swaying this perception towards the biological capabilities of these tumors to produce metastasis, while such rarely develop due to the short patient survival.

Serum Neurofilament Light Chain and Glial Fibrillary Acidic Protein as Potential Diagnostic Biomarkers in Autism Spectrum Disorders: A Preliminary Study

Autism spectrum disorder (ASD) is one of the most common neurodevelopment disorders, characterized by a multifactorial etiology based on the interaction of genetic and environmental factors. Recent evidence supports the neurobiological hypothesis based on neuroinflammation theory. To date, there are no sufficiently validated diagnostic and prognostic biomarkers for ASD. Therefore, we decided to investigate the potential diagnostic role for ASD of two biomarkers well known for other neurological inflammatory conditions: the glial fibrillary acidic protein (GFAP) and the neurofilament (Nfl). Nfl and GFAP serum levels were analyzed using SiMoA technology in a group of ASD patients and in a healthy control group (CTRS), age- and gender-matched. Then we investigated the distribution, frequency, and correlation between serum Nfl and GFAP levels and clinical data among the ASD group. The comparison of Nfl and GFAP serum levels between ASD children and the control group showed a mean value of these two markers significantly higher in the ASD group (sNfL mean value ASD pt 6.86 pg/mL median value ASD pt 5.7 pg/mL; mean value CTRS 3.55 pg/mL; median value CTRS 3.1 pg; GFAP mean value ASD pt 205.7 pg/mL median value ASD pt 155.4 pg/mL; mean value CTRS 77.12 pg/mL; median value CTRS 63.94 pg/mL). Interestingly, we also found a statistically significant positive correlation between GFAP levels and hyperactivity symptoms (p-value <0.001). Further investigations using larger groups are necessary to confirm our data and to verify in more depth the potential correlation between these biomarkers and ASD clinical features, such as the severity of the core symptoms, the presence of associated symptoms, and/or the evaluation of a therapeutic intervention. However, these data not only might shed a light on the neurobiology of ASD, supporting the neuroinflammation and neurodegeneration hypothesis, but they also might support the use of these biomarkers in the early diagnosis of ASD, to longitudinally monitor the disease activity, and even more as future prognostic biomarkers.

Pharmacological effects and therapeutic potential of natural compounds in neuropsychiatric disorders: An update

Neuropsychiatric diseases are a group of disorders that cause significant morbidity and disability. The symptoms of psychiatric disorders include anxiety, depression, eating disorders, autism spectrum disorders (ASD), attention-deficit/hyperactivity disorder, and conduct disorder. Various medicinal plants are frequently used as therapeutics in traditional medicine in different parts of the world. Nowadays, using medicinal plants as an alternative medication has been considered due to their biological safety. Despite the wide range of medications, many patients are unable to tolerate the side effects and eventually lose their response. By considering the therapeutic advantages of medicinal plants in the case of side effects, patients may prefer to use them instead of chemical drugs. Today, the use of medicinal plants in traditional medicine is diverse and increasing, and these plants are a precious heritage for humanity. Investigation about traditional medicine continues, and several studies have indicated the basic pharmacology and clinical efficacy of herbal medicine. In this article, we discuss five of the most important and common psychiatric illnesses investigated in various studies along with conventional therapies and their pharmacological therapies. For this comprehensive review, data were obtained from electronic databases such as MedLine/PubMed, Science Direct, Web of Science, EMBASE, DynaMed Plus, ScienceDirect, and TRIP database. Preclinical pharmacology studies have confirmed that some bioactive compounds may have beneficial therapeutic effects in some common psychiatric disorders. The mechanisms of action of the analyzed biocompounds are presented in detail. The bioactive compounds analyzed in this review are promising phytochemicals for adjuvant and complementary drug candidates in the pharmacotherapy of neuropsychiatric diseases. Although comparative studies have been carefully reviewed in the preclinical pharmacology field, no clinical studies have been found to confirm the efficacy of herbal medicines compared to FDA-approved medicines for the treatment of mental disorders. Therefore, future clinical studies are needed to accelerate the potential use of natural compounds in the management of these diseases.

Liquid biopsies for early diagnosis of brain tumours: in silico mathematical biomarker modelling

Brain tumours are the biggest cancer killer in those under 40 and reduce life expectancy more than any other cancer. Blood-based liquid biopsies may aid early diagnosis, prediction and prognosis for brain tumours. It remains unclear whether known blood-based biomarkers, such as glial fibrillary acidic protein (GFAP), have the required sensitivity and selectivity. We have developed a novel in silico model which can be used to assess and compare blood-based liquid biopsies. We focused on GFAP, a putative biomarker for astrocytic tumours and glioblastoma multi-formes (GBMs). In silico modelling was paired with experimental measurement of cell GFAP concentrations and used to predict the tumour volumes and identify key parameters which limit detection. The average GBM volumes of 449 patients at Leeds Teaching Hospitals NHS Trust were also measured and used as a benchmark. Our model predicts that the currently proposed GFAP threshold of 0.12 ng ml-1 may not be suitable for early detection of GBMs, but that lower thresholds may be used. We found that the levels of GFAP in the blood are related to tumour characteristics, such as vasculature damage and rate of necrosis, which are biological markers of tumour aggressiveness. We also demonstrate how these models could be used to provide clinical insight.

Molecular features of glioblastomas in long-term survivors compared to short-term survivors—a matched-pair analysis

Background

Although glioblastoma (GB) is associated with a devastating prognosis, a small proportion of patients achieve long-term survival rates. We herein present a matched-pair analysis of molecular factors found in long- and short-term survivors (LTS, STS).

Methods

We performed a cross-institutional analysis of 262 patient records and matched a group of 91 LTS (≥ 3 years) with two groups of STS (STS-1, n = 91; STS-2, n = 80). Matching was performed according to age, Karnofsky Performance Status, initial therapy and adjuvant therapy. Molecular factors were compared between LTS (total of 91 patients) v. STS-1, and LTS (subgroup of 80 patients) v. STS-2. We included glial fibrillary acidic protein (GFAP), O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation, isocitrate dehydrogenase 1 (IDH-1); furthermore, the proliferation index was analyzed (Ki-67/MIB-1).

Results

IDH-1 and decreased Ki-67 were numerically associated with LTS but the difference was only significant compared to STS-1 (n.s. v. STS-2). LTS was associated with MGMT promoter hypermethylation (p = 0.013 and p = 0.022) and GFAP expression (p < 0.001 and p = 0.001). Positivity for both factors combined compared to negativity for one factor occurred more often in the LTS group (p = 0.002 and p = 0.006); negativity for both factors combined did not occur in the LTS group.

Conclusion

In this retrospective analysis, GFAP expression and MGMT promoter methylation were associated with LTS. Given the hypothesis-generating nature of our study, these observations should be confirmed in prospective clinical trials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-022-01984-w.

Cerebral astroblastoma with oligodendroglial-like cells: A case report

RATIONALE

Astroblastoma is a rare tumor of the central nervous system with uncertain biological behavior and origin. Its histopathological features have been well established, while, to our knowledge, astroblastoma with oligodendroglial-like cells have not been reported.

PATIENT CONCERNS

A 15-year-old girl presented with nausea, vomiting, headache, and visual disturbance.

DIAGNOSIS

Magnetic resonance imaging revealed a large neoplasm in the left temporal. Histologically, the tumor showed solid and pseudopapillary structure. Immunohistochemical staining showed that the tumor cells were positive for glial fibrillary acidic protein and vimentin. The oligodendroglial-like cells were positive for glial fibrillary acidic protein, vimentin, and oligodendrocyte transcription factor 2. The antigen KI67 labeling index was about 4%. Sequencing for isocitrate dehydrogenase (IDH) 1 codon 132 and IDH2 codon 172 gene mutations showed negative results. Furthermore, fluorescent analysis revealed neither 1p nor 19q deletion in the lesion. Based on these findings, the girl was finally diagnosed as astroblastoma.

INTERVENTIONS

A craniotomy with total excision of the tumor was performed.

OUTCOMES

The follow-up time was 1 year, no evidence of disease recurrence was found in magnetic resonance imaging.

LESSONS

Cerebral astroblastoma with oligodendroglial-like cells is a clinically rare tumor of central nervous system. Clear distinction and diagnosis are critical.

Failure of IVIG in steroid-responsive autoimmune glial fibrillary acidic protein astrocytopathy: A case report

OBJECTIVE

To advocate for high-dose steroids, not intravenous immunoglobulins (IVIG), as first-line treatment for Anti-glial fibrillary acidic protein (GFAP) associated meningoencephalomyelitis.

BACKGROUND

A novel IgG antibody against GFAP was associated with relapsing autoimmune meningoencephalomyelitis.

DESIGN/METHODS

Here, we present an investigational case report to highlight continuing challenges in diagnosing and managing Anti-GFAP associated meningoencephalomyelitis.

RESULTS

Our 45-year-old Asian female presented to the emergency department with an acute onset low-grade fever and back pain associated with headaches, intermittent confusion, vision changes, and hand tremors. A review of systems identified no inciting factors. Past medical history was significant only for chronic Hepatitis B without significant viral load. Neurological exam was significant for decreased visual acuity, high-frequency hand tremor, and gait imbalance. Serum labs were within normal limits. Video electroencephalogram captured tremors without electrographical correlates. Cerebrospinal fluid analysis revealed lymphocytic leukocytosis, elevated protein, and reduced glucose. A wide range of infectious studies including bacterial, viral, and fungal cultures were negative. MRI brain and spine showed leptomeningeal enhancement. CT chest abdomen pelvis were negative. Patient continued to decline clinically, working diagnosis was possible paraneoplastic syndrome with pending laboratory results. She was given a five-day course of intravenous immunoglobulin as a therapeutic trial,hh however, her symptoms did not improve. A broader investigation with repeat lumbar puncture, imaging and serum laboratory failed to provide any additional information. She was treated symptomatically with minimal benefit. A trial of steroids was given with clinical improvement and continued stability. Paraneoplastic panels returned positive for high levels of Anti-GFAP antibody for confirmation of diagnosis.

CONCLUSIONS

Autoimmune GFAP astrocytopathy is a rare cause of meningoencephalomyelitis that remains difficult to diagnose despite emerging laboratory studies. Our case adds to the limited literature by proposing that high-dose steroids, not IVIG, should be the first-line treatment. Further investigations are underway to assess implications of this finding in disease pathophysiology and management.

Receptor Tyrosine Kinase Signaling and Targeting in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is amongst the deadliest of human cancers, with a median survival rate of just over one year following diagnosis. Characterized by rapid proliferation and diffuse infiltration into the brain, GBM is notoriously difficult to treat, with tumor cells showing limited response to existing therapies and eventually developing resistance to these interventions. As such, there is intense interest in better understanding the molecular alterations in GBM to guide the development of more efficient targeted therapies. GBM tumors can be classified into several molecular subtypes which have distinct genetic signatures, and they show aberrant activation of numerous signal transduction pathways, particularly those connected to receptor tyrosine kinases (RTKs) which control glioma cell growth, survival, migration, invasion, and angiogenesis. There are also non-canonical modes of RTK signaling found in GBM, which involve G-protein-coupled receptors and calcium channels. This review uses The Cancer Genome Atlas (TCGA) GBM dataset in combination with a data-mining approach to summarize disease characteristics, with a focus on select molecular pathways that drive GBM pathogenesis. We also present a unique genomic survey of RTKs that are frequently altered in GBM subtypes, as well as catalog the GBM disease association scores for all RTKs. Lastly, we discuss current RTK targeted therapies and highlight emerging directions in GBM research.

Accumulation of amyloid beta in human glioblastomas

Many cancer types are intrinsically associated with specific types of amyloidosis, in which amyloid is accumulated locally inside tumors or systemically. Usually, this condition relates to the hyperproduction of specific amylogenic proteins. Recently, we found that the accumulation of amyloid beta (Aβ) peptide immunofluorescence is linked to glioma cells in mouse tumors. Here we report that amyloid-specific histochemical dyes reveal amyloid accumulation in all human glioma samples. Application of two different antibodies against Aβ peptide (a polyclonal antibody against human Aβ1-42 and a monoclonal pan-specific mAb-2 antibody against Aβ) showed that the amyloid in glioma samples contains Aβ. Amyloid was linked to glioma cells expressing glial-specific fibrillary acidic protein (GFAP) and to glioma blood vessels. Astrocytes close to the glioma site and to affected vessels also accumulated Aβ. We discuss whether amyloid is produced by glioma cells or is the result of systemic production of Aβ in response to glioma development due to an innate immunity reaction. We conclude that amyloid build-up in glioma tumors is a part of the tumor environment, and may be used as a target for developing a novel class of anti-tumor drugs and as an antigen for glioma visualization.

Natural Products and Their Therapeutic Effect on Autism Spectrum Disorder

Autism is a complex neurodevelopmental disorder that is evident in early childhood and can persist throughout the entire life. The disease is basically characterized by hurdles in social interaction where the individuals demonstrate repetitive and stereotyped interests or patterns of behavior. A wide number of neuroanatomical studies with autistic patients revealed alterations in brain development which lead to diverse cellular and anatomical processes including atypical neurogenesis, neuronal migration, maturation, differentiation, and degeneration. Special education programs, speech and language therapy, have been employed for the amelioration of behavioral deficits in autism. Although commonly prescribed antidepressants, antipsychotics, anticonvulsants, and stimulants have revealed satisfactory responses in autistic individuals, adverse side effects and increased risk of several other complications including obesity, dyslipidemia, diabetes mellitus, thyroid disorders, etc. have compelled the researchers to turn their attention toward herbal remedies. Alternative approaches with natural compounds are on continuous clinical trial to confirm their efficacy and to understand their potential in autism treatment. This chapter aims to cover the major plant-based natural products which hold promising outcomes in the field of reliable therapeutic interventions for autism.

Importance of GFAP isoform-specific analyses in astrocytoma

Gliomas are a heterogenous group of malignant primary brain tumors that arise from glia cells or their progenitors and rely on accurate diagnosis for prognosis and treatment strategies. Although recent developments in the molecular biology of glioma have improved diagnosis, classical histological methods and biomarkers are still being used. The glial fibrillary acidic protein (GFAP) is a classical marker of astrocytoma, both in clinical and experimental settings. GFAP is used to determine glial differentiation, which is associated with a less malignant tumor. However, since GFAP is not only expressed by mature astrocytes but also by radial glia during development and neural stem cells in the adult brain, we hypothesized that GFAP expression in astrocytoma might not be a direct indication of glial differentiation and a less malignant phenotype. Therefore, we here review all existing literature from 1972 up to 2018 on GFAP expression in astrocytoma patient material to revisit GFAP as a marker of lower grade, more differentiated astrocytoma. We conclude that GFAP is heterogeneously expressed in astrocytoma, which most likely masks a consistent correlation of GFAP expression to astrocytoma malignancy grade. The GFAP positive cell population contains cells with differences in morphology, function, and differentiation state showing that GFAP is not merely a marker of less malignant and more differentiated astrocytoma. We suggest that discriminating between the GFAP isoforms GFAPδ and GFAPα will improve the accuracy of assessing the differentiation state of astrocytoma in clinical and experimental settings and will benefit glioma classification.

Immunohistochemical comparative analysis of GFAP, MAP - 2, NOGO - A, OLIG - 2 and WT - 1 expression in WHO 2016 classified neuroepithelial tumours and their prognostic value

Immunohistochemistry is routinely used in differential diagnosis of tumours of the central nervous system (CNS). The latest 2016 WHO 2016 revision now includes molecular data such as IDH mutation and 1p/19q codeletion thus restructuring glioma classification. Direct comparative information between commonly used immunohistochemical markers for glial tumours GFAP, MAP - 2, NOGO - A, OLIG - 2 and WT - 1 concerning quality and quantity of expression and their relation to the new molecular markers are lacking. We therefore compared the immunohistochemical staining results of all five antibodies in 34 oligodendrogliomas, 106 ependymomas and 423 astrocytic tumours. GFAP expression was reduced in cases with higher WHO grade, oligodendroglial differentiation and in IDH wildtype diffuse astrocytomas. By contrast MAP - 2 expression was significantly increased in diffuse astrocytomas with IDH mutation, while NOGO - A expression was not associated with any molecular marker. WT - 1 expression was significantly decreased in tumours with IDH mutation and ATRX loss. OLIG - 2 was increased in IDH-mutant grade II astrocytomas and in cases with higher proliferation rate. In univariate survival analysis high WT - 1 expression was significantly associated with worse outcome in diffuse astrocytic tumours (log rank p < 0.0001; n = 211; median time: 280 days vs 562 days). None of the markers was prognostic in multivariate survival analysis. Among the evaluated markers MAP - 2, OLIG - 2 and WT - 1 showed the best potential to separate between glioma entities and can be recommended for a standardized immunohistochemical panel.

Pediatric low-grade gliomas: how modern biology reshapes the clinical field

Low-grade gliomas represent the most frequent brain tumors arising during childhood. They are characterized by a broad and heterogeneous group of tumors that are currently classified by the WHO according to their morphological appearance. Here we review the clinical features of these tumors, current therapeutic strategies and the recent discovery of genomic alterations characteristic to these tumors. We further explore how these recent biological findings stand to transform the treatment for these tumors and impact the diagnostic criteria for pediatric low-grade gliomas.

Effect of Naringenin on metabolic markers, lipid profile and expression of GFAP in C6 glioma cells implanted rat's brain

BACKGROUND

Naringenin, a flavanone, has been reported to exhibit a wide range of pharmacological properties including antitumor activity.

PURPOSE

We wanted to test the efficacy of Naringenin on C6 glioma cells-implanted into rats was investigated.

METHODS

Biochemical and immunohistochemical methods were used for analyzing various markers.

RESULTS

Injection of C6 glioma cells into rat brain resulted in increased metabolic markers {Lactatate Dehydrogenase (LDH), 5' Nucleotidase 5'ND), creatine kinase (CK), Hexokinase (HK) and Glucose 6-phosphate dehydrogenase (G6PD)} and lipid profile (triglycerides, free fatty acids, phos-pholipids, total cholesterol and free cholesterol). Oral administration of Naringenin (50 mg /kg of BW for 30 days) significantly altered this biochemical profile. Further, the immuno fluorescence expression of Glial fibrilary acidic protein (GFAP) was also studied.

CONCLUSION

In C6 glioma cells-implanted rats, increased expression of GFAP was noted on treatment with Naringenin. These observations suggest that Naringenin may participate by inhibiting glial cell tumorigenesis.

A case of multinodular high-grade neuroepithelial tumor with ependymal differentiation

We describe a rare case of multinodular cerebral neuroepithelial tumor with ependymal differentiation. A 65-year-old man experienced loss of consciousness with an obscure episode of seizure attack. Magnetic resonance images disclosed a lesion located in the left temporal lobe and the insular cortex. The tumor was partially removed. Histologically, the tumor showed infiltrating multinodular tumor nodules in the cerebrum. Each nodule was well demarcated and composed of clear cells with perinuclear halos, intermingled fibrillary cells, and poorly differentiated neuroepithelial cells with mitotic activity. Immunohistochemically, clear cells showed dot-like positivity for epithelial membrane antigen. Fibrillary cells were positive for vimentin and nestin, whereas only a few glial fibrillary acidic protein-immunopositive cells were seen. We conclude that this tumor, being microscopically characterized by multinodular tumor nodules, was a high-grade neuroepithelial tumor with ependymal differentiation.

Expression of peripherin in the brain of macaques (Macaca mulatta and Macaca fascicularis) occurs in astrocytes rather than neurones and is associated with encephalitis

Peripherin is a member of the type III intermediate filament family, expressed in neurones of the peripheral nervous system of many species and in a discrete subpopulation of neurones of the central nervous system (CNS) during early development in rodents. Previous studies on rats have shown that peripherin immunoreactivity increased significantly in cell bodies of spinal motor neurones following axonal injury. Our study examined the expression of peripherin in the cerebrum of normal macaques (Macaca mulatta and Macaca fascicularis) and those with encephalitis of viral (simian immunodeficiency virus and simian virus 40) or autoimmune (experimental allergic encephalomyelitis) aetiology. Immunohistochemistry, immunoelectronmicroscopy, immunofluorescence and confocal microscopy were performed on tissue sections using antibodies against cell-specific markers and peripherin. Peripherin-positive cells were absent in the cerebrum of normal macaques of all ages examined, whereas animals with encephalitis had peripherin-positive cells associated with inflammatory infiltrates. Further evaluation revealed that these peripherin-positive cells were not neurones, but were predominantly astrocytes expressing glial fibrillary acidic protein. Our study suggests that peripherin is not neurone-specific in the CNS of macaques; peripherin is expressed in astrocytes of animals with encephalitis.

Expression of multiple larger-sized transcripts for several genes in oligodendrogliomas: potential markers for glioma subtype

Astrocytomas and oligodendrogliomas are two brain tumors that follow different clinical courses. Although many of these tumors can be identified based on standard histopathological criteria, a significant percentage present notable problems in diagnosis. To identify markers that might prove useful in distinguishing glioma subtypes, we prepared and analyzed cDNA libraries for differential expression of genes in an astrocytoma (grade II), an oligodendroglioma (grade II), and a meningioma (benign). The tumor libraries were compared by sequencing randomly selected clones and tabulating the expression frequency of each gene. In addition to identifying several genes previously reported or expected to be differentially expressed among these tumors, several potential new brain tumor markers were identified and confirmed by Northern blot analysis of a panel of brain tumors. A surprising result of this analysis was the observation that several larger-sized transcripts for various genes were predominantly expressed in the oligodendroglioma tumors, when compared to the other brain tumors or in non-tumor gray matter. These findings are consistent with different pre-mRNA splicing patterns observed between oligodendrogliomas and astrocytomas. In support of this hypothesis, our screen revealed significantly higher levels of two hnRNP A1 transcripts in oligodendrogliomas. hnRNP A1 is a component of the spliceosome whose expression levels affect splice site selection in vivo. The preferential expression of larger-sized transcripts for several genes in oligodendrogliomas may be useful for distinguishing astrocytic and oligodendroglial gliomas.

Congenital glioblastoma multiforme: a report of three cases and a review of the literature

The clinical histories, histologic features, and immunohistochemical staining patterns for glial fibrillary acidic protein, vimentin, p53, and epidermal growth factor receptor (EGFR) of three cases of congenital glioblastoma multiforme are given and previous case reports are reviewed. Of the three cases reported in this series, two have had long-term survivals of greater than 2 1/2 and 5 1/2 years after surgery and surgery followed by chemotherapy, respectively. Both of these cases also demonstrated p53 protein accumulation, a finding in pediatric glioblastoma multiforme associated with poor prognosis. The third case occurred in an infant who died at birth and demonstrated a well-circumscribed tumor that did not invade adjacent brain parenchyma. Considering these three cases, the biological behavior in congenital glioblastoma multiforme may not be unfavorable as portrayed in the literature or as seen in its adult counterpart.

Semiquantitative postembedding characterization of intermediate filaments in central nervous system lesions using immunoelectron microscopy

Standardized postembedding immunoelectron microscopy was performed to demonstrate glial fibrillary acidic protein (GFAP) and vimentin in individual intermediate filaments to determine the diagnostic value of demonstrating ultrastructural and immunophenotypic characteristics of intermediate filaments in routine brain biopsy specimens. Dual expression of GFAP and vimentin was observed in the astroblastoma and astrocytes of Alexander's disease. The antigen availability for vimentin, however, was too low to allow reliable assessment of the GFAP:vimentin ratio in individual intermediate filaments and/or filament bundles. In meningioma, only vimentin positive intermediate filaments were found. GFAP positive intermediate filaments were present in all other specimens except the oligodendroglial components of the mixed glioma, which were devoid of intermediate filaments. GFAP positivity in the filamentous periphery and electron-dense core of Rosenthal fibers was demonstrated. Technical and tissue processing factors had a significant effect on particle density values obtained for individual specimens. Although the number, distribution, and density of glial intermediate filaments varies in different astroglial entities, correlation of particle density values determined by immunoelectron microscopy with relative GFAP concentrations in different lesions requires utmost caution. Nevertheless, application of the postembedding approach to routinely fixed biopsy specimens indicated an association of different entities with the exclusive presence of GFAP and/or vimentin in individual intermediate filaments, thus emphasizing the diagnostic value of intermediate filament typing for pathological characterization.

Proteins of the intermediate filament cytoskeleton as markers for astrocytes and human astrocytomas

There is a pressing need for a more accurate system of classifying human astrocytomas, one that is based on morphologic characteristics and that could also make use of distinctive biochemical markers. However, little is known about the phenotypic characteristics of astrocytomas. Recent studies have shown that the expression of proteins comprising the intermediate filament (IF) cytoskeleton of astrocytic cells is developmentally regulated. It is our hypothesis that this changing protein profile can be used as the basis of a system for clearly and objectively classifying astrocytomas. A spectrum of human astrocytomas has been examined by immunofluorescence microscopy employing antibodies to several IF structural subunit proteins (GFAP, vimentin, and keratins) and an IF-associated protein, IFAP-300kDa. These proteins occupy unique temporal niches in the cytogenesis of the astrocytic cells: keratins in cells of the neuroectoderm; vimentin and IFAP-300kDa in radial glia and immature glia; GFAP in mature astrocytes; and vimentin in some mature astrocytes. In agreement with previous reports, our immunofluorescence studies have revealed both GFAP and vimentin in all astrocytoma specimens. Two new observations, however, are of particular interest: IFAP-300kDa is detectable in all astrocytic tumors, and the proportion of keratin-containing cells present in the astrocytomas is in direct relationship to the degree of the malignancy. Because IFAP-300kDa is not present in either normal mature or reactive astrocytes, this protein appears to represent a specific marker of transformed (malignant) astrocytes. If it is presumed that higher malignancy grades represent the most dedifferentiated cellular state of the astrocytes, the presence of keratin-containing cells is not totally unexpected, given the ectodermal (epithelial) origin of the CNS. Specific developmentally regulated proteins of the IF cytoskeleton thus appear to hold great potential as diagnostic markers of astrocytomas and as tools for investigating the biology of these tumors.

Ultrastructural characteristics of glial fibrillary acidic protein expression in epoxy resin-embedded human brain tumors

Thirteen surgically removed, epoxy resin (Durcupan ACM or Epon 812)-embedded human brain tumors were examined for glial fibrillary acidic protein (GFAP) content in semithin and ultrathin sections with the immunogold-silver staining method. Mild aldehyde fixation and the hydrophobic resin embedding did not interfere with the antigenicity, since silver intensification of the immunogold marker provided excellent visualization of the reaction on both light microscopic and ultrastructural levels. The GFAP reaction was usually localized on the glial intermediate filament bundles, usually correlating well with the amount of filaments. The unstained filamental regions of two ependymomas might correspond to the vimentin expression revealed by double labeling in semithin sections. Occasional GFAP immunopositivity without filamental appearance was observed in one of the oligodendrogliomas, as patchy electron-dense cytoplasmic corpuscules, in Rosenthal fibers and in some mainly necrobiotic tumor cells, reflecting a possible connection with glial filaments.

Immunohistochemistry in childhood brain tumors: what are the facts?

In the past, contradictory results have been reported concerning the specificity of neuronal or glial cell markers. However, we have investigated this aspect in a large group of more than 550 brain tumors (among them 60 medulloblastomas). These contradictions can easily be explained by considering two basic facts. First, every neoplastic cell population, especially in embryonic tumors, diffusely infiltrates the brain tissue: non-neoplastic cells, intermingled with tumor cells, can therefore give rise to immunohistochemical and histogenetic misinterpretations. Second, different cell markers can be expressed by one and the same cell (e.g., GFAP, NSE, vimentin), making nosological interpretation of the tumor difficult, impossible, or at best rather subjective. Clear-cut marker positivity is mostly found in the differentiated tumors for which the nosological classification is already clear by the usual histological methods. Only synaptophysin seems to be a reliable marker for neurogenic cells. In embryonic brain tumors (so-called PNET), no correlations between the presence of a given cell marker and the biological behavior of the tumor have so far been detected.

Late pleuropulmonary metastases of a cerebral ependymoma

A patient with a 12-year history of occipital ependymoma was found to have late pleuropulmonary metastases without recurrence of the primary tumor. The pleural metastases were diagnosed by histologic, ultrastructural features and finally by glial fibrillary acidic protein (GFAP) labeling positive reaction. This case is unique because of the long interval between occurrence of the initial tumor and the metastases, and because of the apparent quiescence of the cerebral lesion when the pleuropulmonary metastases were discovered.

Immunohistochemical localization of apolipoprotein E in human glial neoplasms

Immunocytochemical analyses revealed the presence and distribution of apolipoprotein E (apo E) in normal human brain tissue as well as in 77 human intracranial neoplasms. In normal brain tissues, the perikarya of astrocytes exhibited a strong positive reaction, whereas the Bergmann glia were stained to a moderate degree. However, no immunoreactivity was observed with neurons, oligodendrocytes, ependymal cells, and choroidal epithelium. Among the intracranial neoplasms, oligodendroglioma, choroid plexus papilloma, hemangioblastoma, primary malignant lymphoma, neurinoma, meningioma, pituitary adenoma, and craniopharyngioma were all negative. Immunoreactivity in the peripheral neuroblastoma was nil. However, the perikarya of astrocytomas and glioblastomas showed a positive reaction. Analyses on the degree of anaplasia and the amount of apo-E as an intensity of immunostaining showed a negative correlation. The astrocytic elements were stained in mixed oligoastrocytomas and medulloblastomas with glial differentiation. A few cases of ependymomas showed weak perikaryal immunostaining. Western blot analyses with anti-apo E antibody of a freshly prepared surgical specimen with astrocytomas revealed a single band with a molecular weight of approximately 37,000. The well differentiated cultured human astrocytoma cells secreted apo E into the medium. These lines of evidence suggest that apo E may serve as a potential marker specific for astrocytomas and glioblastomas, as well as an indicator of astrocytic tumor cell differentiation. The apo E localization in human brain tumors could be clinically relevant and diagnostically useful.

Gamma-enolase and glial fibrillary acidic protein in nervous system tumors. An immunohistochemical study using specific monoclonal antibodies

A large series of central and peripheral nervous system tumors was studied for the presence of glial fibrillary acidic protein (GFAP) and gamma-enolase (neuron-specific enolase, NSE), using specific monoclonal antibodies (mAbs). Occurrence in and specificity of GFAP to glial and mixed tumors was confirmed and depended on the malignancy grade and features such as meningeal invasion. Using a well-characterized mAb, gamma-enolase was demonstrated in neuronal, as well as in a whole range of non-neuronal tumors. This lack of specificity of gamma-enolase prohibits its use as an exclusive neuronal marker. Nevertheless quantization or comparison with other types of enolases could still prove to be useful in well-defined situations. The advantages inherent to mAbs and a highly sensitive detection system turn GFAP stainings into a specific and readily reproducible technique.