The molecular biology of WHO grade I astrocytomas

Targeting the EGFR pathway: An alternative strategy for the treatment of tuberous sclerosis complex?

INTRODUCTION

Tuberous sclerosis complex (TSC) is caused by variants in TSC1/TSC2, leading to constitutive activation of the mammalian target of rapamycin (mTOR) complex 1. Therapy with everolimus has been approved for TSC, but variations in success are frequent. Recently, caudal late interneuron progenitor (CLIP) cells were identified as a common origin of the TSC brain pathologies such as subependymal giant cell astrocytomas (SEGA) and cortical tubers (CT). Further, targeting the epidermal growth factor receptor (EGFR) with afatinib, which is expressed in CLIP cells, reduces cell growth in cerebral TSC organoids. However, investigation of clinical patient-derived data is lacking.

AIMS

Observation of EGFR expression in SEGA, CT and focal cortical dysplasia (FCD) 2B human brain specimen and investigation of whether its inhibition could be a potential therapeutic intervention for these patients.

METHODS

Brain specimens of 23 SEGAs, 6 CTs, 20 FCD2Bs and 17 controls were analysed via immunohistochemistry to characterise EGFR expression, cell proliferation (via Mib1) and mTOR signalling. In a cell-based assay using primary patient-derived cells (CT n = 1, FCD2B n = 1 and SEGA n = 4), the effects of afatinib and everolimus on cell proliferation and cell viability were observed.

RESULTS

EGFR overexpression was observed in histological sections of SEGA, CT and FCD2B patients. Both everolimus and afatinib decreased the proliferation and viability in primary SEGA, tuber and FCD2B cells.

CONCLUSION

Our study demonstrates that EGFR suppression might be an effective alternative treatment option for SEGAs and tubers, as well as other mTOR-associated malformations of cortical development, including FCD2B.

Calcified Pilocytic Astrocytomas and Calcifying Pseudoneoplasms of the Neuraxis: A Diagnostic Challenge

Pilocytic astrocytoma (PA), recognized as the most prevalent central nervous system (CNS) tumor, has long been associated with calcifications, a characteristic often attributed to benign or indolent growth patterns. In this study, we explored the calcified attributes in these tumors that beckon a deeper understanding. This is a retrospective study, on a set of seven cases, with a histopathological diagnosis of pilocytic astrocytoma with calcifications and psammoma bodies (PB). Despite an encouraging overall survival outcome, the recurrence in four cases cast some doubt on the conventional classification. The histological study of these cases revealed a spectrum of calcifications, varying in size and morphology, all of which exhibited positive reactivity to glial fibrillary acidic protein (GFAP), osteoconduction, and osteopontin. Notably, the immunohistochemistry showed hyaline bodies displaying an atypical immune profile, strikingly negative for vimentin and GFAP, and a robust positivity for epidermal growth factor receptors (EGFR), tumor necrosis factor-alpha (TNF-α), and interleukin 1 beta (IL-1β). These results stimulated speculation that the identity of these calcified tumors may have extended and potentially embraced the realm of calcifying pseudoneoplasms of the neuraxis (CAPNON), underscored by intense pilot gliosis. This study transcends mere anatomical exploration; it delves into the intricacies of calcified tumors, casting a spotlight on the dynamic interplay between PA and CAPNON. As we traverse the frontiers of neuro-oncology, these findings pave the way for innovative avenues in the diagnostics and therapeutics of these tumors.

Pathology of hereditary renal cell carcinoma syndromes: Tuberous sclerosis complex (TSC)

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disease characterized by hamartomatous tumors involving multiple organs such as the brain, skin, heart, lung and kidney. TSC is caused by inactivating mutations in TSC1/TSC2, which encodes hamartin and tuberin, respectively, and forms a complex that regulates mechanistic target of rapamycin complex 1 (mTORC1), resulting in cell overgrowth and oncogenesis. Since a leading cause of morbidity and mortality in TSC relates to chronic kidney disease and the ability to preserve renal function, this review describes the important pathologic findings in TSC-associated renal neoplasms and their correlating sporadic counterparts. The most common renal tumor in TSC patients are AMLs, followed by a heterogeneous spectrum of renal epithelial tumors, which may provide clues to establishing a diagnosis of TSC.

Cytogenomic Analysis of Long-Term Epilepsy-Associated Tumors Using an Array-Based CGH Strategy

A palette of copy number changes in long-term epilepsy-associated tumors (LEATs) have been reported, but the data are heterogeneous. To better understand the molecular basis underlying the development of LEATs, we performed array-comparative genomic hybridization analysis to investigate chromosomal imbalances across the entire genome in 8 cases of LEATs. A high number of aberrations were found in 4 patients, among which deletions predominated. Both whole-chromosome and regional abnormalities were observed, including monosomy 19, deletion of 1p, deletions of 4p, 12p, and 22q, and gain of 20p. The common altered regions are located mainly on chromosomes 19 and 4p, identifying genes potentially involved in biological processes and cellular mechanisms related to tumorigenesis. Our study highlights new genomic alterations and reinforces others previously reported, offering new molecular insights that may help in diagnosis and therapeutic decision-making.

Clinical characteristics and long-term surgical outcomes of spinal pilocytic astrocytoma: a report of twenty cases

BACKGROUND

Primary spinal pilocytic astrocytoma (PA) is an extremely rare low-grade astrocytoma with unclear natural history. The demographic characteristics, imaging features, and long-term surgical outcomes have not been clarified due to low prevalence and limited reports.

METHODS

A retrospective review within a single institution between 2004 and 2018 of all patients with pathologically proven PA was conducted. Patient data including demographics, radiographic features, treatment modalities, and long-term outcomes were evaluated.

RESULTS

Twenty consecutive patients were identified, and 16 (80%) were male patients, with a mean age at presentation of 29 ± 13 years. The lesion was primarily located in cervical (n = 10, 50%), thoracic (n = 7, 35%), cervico-thoracic junction (n = 2), and lumbar level (n = 1, 5%). The tumor had a mean extension of 4 ± 2 (1-7) vertebral segments. Most PAs were located eccentrically (n = 16, 80%), with most being heterogeneous in appearance (cystic and solid) or purely cystic (n = 14, 70%), and had unclear margins (n = 16, 80%). Eleven patients (55%) had associated syringomyelia. Gross total resection (GTR) was achieved in 11 (55%) patients, and subtotal resection (STR) in 9 (45%). During a mean follow-up of 104 ± 56 months, 2 patients died and recurrence was found in 4 patients (20%), translating to a mean progression-free survival of 21 ± 11 months.

CONCLUSION

Primary spinal PA is a rare entity with acceptable progression-free survival if treated appropriately. Surgical resection may provide reasonable prolongation of survival, and GTR should be achieved if possible. A close follow-up is recommended especially for residual lesions, and a further in-depth investigation of molecular biomarkers is needed to stratify risk and prognostic factors.

A novel PTPRZ1-ETV1 fusion in gliomas

The aggressive nature of malignant gliomas and their genetic and clinical heterogeneity present a major challenge in their diagnosis and treatment. Development of targeted therapy brought attention on detecting novel gene fusions, since they represent promising therapeutic targets (eg, TRK inhibitors in NTRK fusion-positive tumors). Using targeted next-generation sequencing, we prospectively analyzed 205 primary brain tumors and detected a novel PTPRZ1-ETV1 fusion transcript in 11 of 191 (5.8%) gliomas, including nine glioblastomas, one anaplastic oligodendroglioma and one pilocytic astrocytoma. PTPRZ1-ETV1 fusion was confirmed by RT-PCR followed by Sanger sequencing, and in-silico analysis predicted a potential driver role. The newly detected fusion consists of the PTPRZ1 promoter in frame with the highly conserved DNA-binding domain of ETV1 transcription factor. The ETV1 and PTPRZ1 genes are known oncogenes, involved in processes of tumor development. ETV1 is a member of the ETS family of transcription factors, already known oncogenic drivers in Ewing sarcoma, prostate cancer and gastrointestinal stromal tumors, but not in gliomas. Its overexpression contributes to tumor growth and more aggressive tumor behavior. PTPRZ1 is already considered to be a tumor growth promoting oncogene in gliomas. In 8%-16% of gliomas, PTPRZ1 is fused to the MET oncogene, resulting in a PTPRZ1-MET fusion, which is associated with poorer prognosis but is also a positive predictive biomarker for treatment with kinase inhibitors. In view of the oncogenic role that the two fusion partners, PTPRZ1 and ETV1, exhibit in other malignancies, PTPRZ1-ETV1 fusion might present a novel potential therapeutic target in gliomas. Although histopathological examination of PTPRZ1-ETV1 fusion-positive gliomas did not reveal any specific or unique pathological features, and the follow-up period was too short to assess prognostic value of the fusion, careful monitoring of patients and their response to therapy might provide additional insights into the prognostic and predictive value of this novel fusion.

Comparable Genomic Copy Number Aberrations Differ across Astrocytoma Malignancy Grades

A collection of intracranial astrocytomas of different malignancy grades was analyzed for copy number aberrations (CNA) in order to identify regions that are driving cancer pathogenesis. Astrocytomas were analyzed by Array Comparative Genomic Hybridization (aCGH) and bioinformatics utilizing a Bioconductor package, Genomic Identification of Significant Targets in Cancer (GISTIC) 2.0.23 and DAVID software. Altogether, 1438 CNA were found of which losses prevailed. On our total sample, significant deletions affected 14 chromosomal regions, out of which deletions at 17p13.2, 9p21.3, 13q12.11, 22q12.3 remained significant even at 0.05 q-value. When divided into malignancy groups, the regions identified as significantly deleted in high grades were: 9p21.3; 17p13.2; 10q24.2; 14q21.3; 1p36.11 and 13q12.11, while amplified were: 3q28; 12q13.3 and 21q22.3. Low grades comprised significant deletions at 3p14.3; 11p15.4; 15q15.1; 16q22.1; 20q11.22 and 22q12.3 indicating their involvement in early stages of tumorigenesis. Significantly enriched pathways were: PI3K-Akt, Cytokine-cytokine receptor, the nucleotide-binding oligomerization domain (NOD)–like receptor, Jak-STAT, retinoic acid-inducible gene (RIG)-I-like receptor and Toll-like receptor pathways. HPV and herpex simplex infection and inflammation pathways were also represented. The present study brings new data to astrocytoma research amplifying the wide spectrum of changes that could help us identify the regions critical for tumorigenesis.

Methylation profiling of paediatric pilocytic astrocytoma reveals variants specifically associated with tumour location and predictive of recurrence

Childhood pilocytic astrocytomas (PA) are low-grade tumours with an excellent prognosis. However, a minority, particularly those in surgically inaccessible locations, have poorer long-term outcome. At present, it is unclear whether anatomical location in isolation, or in combination with underlying biological variation, determines clinical behaviour. Here, we have tested the utility of DNA methylation profiling to inform tumour biology and to predict behaviour in paediatric PA. Genome-wide DNA methylation profiles were generated for 117 paediatric PAs. Using a combination of analyses, we identified DNA methylation variants specific to tumour location and predictive of behaviour. Receiver-operating characteristic analysis was used to test the predictive utility of clinical and/or DNA methylation features to classify tumour behaviour at diagnosis. Unsupervised analysis distinguished three methylation clusters associated with tumour location (cortical, midline and infratentorial). Differential methylation of 5404 sites identified enrichment of genes involved in 'embryonic nervous system development'. Specific hypermethylation of NEUROG1 and NR2E1 was identified as a feature of cortical tumours. A highly accurate method to classify tumours according to behaviour, which combined three clinical features (age, location and extent of resection) and methylation level at a single site, was identified. Our findings show location-specific epigenetic profiles for PAs, potentially reflecting their cell type of origin. This may account for differences in clinical behaviour according to location independent of histopathology. We also defined an accurate method to predict tumour behaviour at diagnosis. This warrants further testing in similar patient cohorts.

[Astrocytoma and epilepsy. Clinical case]

BACKGROUND

Pilocytic astrocytoma is a rare tumour, usually occurring in paediatric ages, and mainly located in the posterior fossa. It can cause hydrocephalus and intracranial hypertension and, less frequently, seizures, or a focal neurological deficit. The main imaging study by magnetic resonance imaging, which shows a tumour with solid and cystic components without peri-lesional swelling. The election treatment is surgical, and the patient is considered cured if a total resection is accomplished.

CLINICAL CASE

The case is presented of 22-year-old female patient with a supratentorial pilocytic astrocytoma and epilepsy. Histopathology reported a low grade glial proliferation, with an extensive fibrillar matrix, small cells without atypia, extensive calcifications and piloid areas consisting of bipolar fusiform cells, and some Rosenthal fibres. There were also spongiotic areas consisting of multipolar cells and associated microcysts. The final report was a pilocytic astrocytoma.

CONCLUSIONS

Pilocytic astrocytoma is more frequent in paediatric patients and in the posterior fossa. The case presented is of a young female adult with supratentorial location, making it a special case. The surgery achieved a total resection. The long-term prognosis is good, but it is necessary to perform a follow-up, particularly in adult patients because of a higher risk of recurrence.

The potential for epigenetic analysis of paediatric CNS tumours to improve diagnosis, treatment and prognosis

Tumours of central nervous system (CNS) origin are the second most prevalent group of cancers in children, yet account for the majority of childhood cancer-related deaths. Such tumours show diverse location, cell type of origin, disease course and long-term outcome, both across and within tumour types, making treatment problematic and contributing to the relatively modest progress in reducing mortality over recent decades. As technological advances begin to reveal the genetic landscape of all cancers, it is becoming increasingly clear that genetic disruption represents only one 'layer' of molecular disruption associated with disease aetiology. Obtaining a full understanding of tumour behaviour requires an understanding of the cellular and molecular pathways disrupted during tumourigenesis, particularly in relation to gene expression. The utility of such an approach has allowed stratification of cancers such as medulloblastoma into subgroups based on molecular features, with potential to refine risk prediction. Given that epigenetic disruption is a universal feature of all human cancers, it is logical to speculate that interrogating epigenetic marks may help to further define the molecular profile, and therefore the clinical trajectory, of tumours. An integrated approach to build a molecular 'signature' of individual tumours that incorporates traditional morphological and demographic information, genetic and transcriptome analysis, in addition to epigenomics (DNA methylation and non-coding RNA analysis), offers tremendous promise to (i) inform treatment approach, (ii) facilitate accurate early identification (preferably at diagnosis) of variable risk groups (both good and poor prognosis groups), and (iii) track disease progression in childhood CNS tumours.

Genetic changes observed in a case of adult pilocytic astrocytoma revealed by array CGH analysis

BACKGROUND

A palette of copy number changes in a case of adult pilocytic astrocytoma analyzed by Array Comparative Genomic Hybridization (aCGH) is presented. Pilocytic astrocytomas are specific gliomas that are benign and biologically distinct and the molecular mechanisms responsible for their development remain unexplained. The aCGH was performed using SurePrint G3 Human CGH microarrays 4 × 180 K (Agilent Technologies). To ascertain whether some of the aberrations were of constitutive nature, we also analyzed the blood sample from the same patient.

RESULTS

The result of aCGH analysis demonstrated differences in the tumor tissue when compared to normal control on the array and also to autologous DNA from patient's blood. The total number of aberrations found in our case was 41 including 37 deletions and 4 amplifications. Whole chromosomal gains and losses were not observed. Collectively, our results showed three deletions and one amplification at 1p, two deletions at 2q, two deletions at 4q, two deletion at 5q, two deletions at 7p and two deletions at 7q; there were also three deletions at 8q, one deletion at 9p, one deletion at 10p, three deletions and one amplification at 10q. Chromosome 11 showed two deletions at 11p, while there was one deletion at 12p and one at 12q. Four deletions at 14q; two deletions at 15q, one amplification at 17q and one deletion at 17q; one deletion at 18p, two deletions at 22q and finally one deletion at Xp and one deletion and one amplification at Xq. Among the signaling pathways, olfactory transduction, Fc gamma R-mediated phagocytosis and p53 signaling pathway showed significant enrichment ascertained by gene ontology (GO) analysis using the DAVID software.

CONCLUSIONS

Our aCGH analysis is bringing subtle genomic alterations thus broadening genetic spectrum of adult pilocytic astrocytoma in order to offer new molecular biomarkers that will help in diagnostics and therapeutic decision-making.

Response of recurrent BRAFV600E mutated ganglioglioma to Vemurafenib as single agent

Background

Ganglioglioma (GG) and pilocytic astrocytoma (PA) represent the most frequent low-grade gliomas (LGG) occurring in paediatric age. LGGs not amenable of complete resection (CR) represent a challenging subgroup where traditional treatments often fail. Activation of the MAP Kinase (MAPK) pathway caused by the BRAFV600E mutation or the KIAA1549-BRAF fusion has been reported in pediatric GG and PA, respectively.

Case presentation

We report on a case of BRAFV600E mutated cervicomedullary GG treated with standard chemotherapy and surgery. After multiple relapse, BRAF status was analyzed by immunohistochemistry and sequencing showing a BRAFV600E mutation. Treatment with Vemurafenib as single agent was started. For the first time, a radiological and clinical response was obtained after 3 months of treatment and sustained after 6 months.

Conclusion

Our experience underline the importance of understanding the driver molecular alterations of LGG and suggests a role for Vemurafenib in the treatment of pediatric GG not amenable of complete surgical resection.