Vascularity and angiogenesis as predictors of growth in optic pathway/hypothalamic gliomas

MOST wanted: navigating the MAPK-OIS-SASP-tumor microenvironment axis in primary pediatric low-grade glioma and preclinical models

Understanding the molecular and cellular mechanisms driving pediatric low-grade glioma (pLGG)-the most prevalent brain tumor in children-is essential for the identification and evaluation of novel effective treatments. This review explores the intricate relationship between the mitogen-activated protein kinase (MAPK) pathway, oncogene-induced senescence (OIS), the senescence-associated secretory phenotype (SASP), and the tumor microenvironment (TME), integrating these elements into a unified framework termed the MAPK/OIS/SASP/TME (MOST) axis. This integrated approach seeks to deepen our understanding of pLGG and improve therapeutic interventions by examining the MOST axis' critical influence on tumor biology and response to treatment. In this review, we assess the axis' capacity to integrate various biological processes, highlighting new targets for pLGG treatment, and the need for characterized in vitro and in vivo preclinical models recapitulating pLGG's complexity to test targets. The review underscores the need for a comprehensive strategy in pLGG research, positioning the MOST axis as a pivotal approach in understanding pLGG. This comprehensive framework will open promising avenues for patient care and guide future research towards inventive treatment options.

Development and Validation of a Liquid-Liquid Phase Separation-Related Gene Signature as Prognostic Biomarker for Low-Grade Gliomas

Aim

To explore whether the liquid-liquid phase separation- (LLPS-) related genes were potential prognostic markers that could contribute to the further classification of low-grade gliomas (LGGs).

Methods

The LLPS-related genes were subjected to functional enrichment analysis. The univariable, least absolute shrinkage and selection operator, and multivariable stepwise Cox regression analyses were performed to develop an LLPS-related gene signature (GS) in the discovery data set. The biological characteristics of the high-risk LGG were explored using gene set enrichment analysis. Two independent external data sets were used to validate the LLPS-related GS.

Results

LLPS-related genes are involved in multiple important cancer-related biological processes and pathways in LGG. Nine LLPS-related genes were identified to construct the LLPS-related GS, which was significantly associated with the prognosis of LGG patients. The LLPS-related GS could successfully divide patients with LGG into high- and low-risk groups, and the high-risk group showed a poorer prognosis than the low-risk group. Furthermore, the LLPS-related GS was independent of IDH and 1p19q status. Several cancer-related pathways may be more active in high-risk LGGs, such as IL6 JAK STAT3 signaling pathway. The LLPS-related GS was successfully validated with two independent external data sets.

Conclusion

We developed and validated a novel LLPS-related GS for risk stratification of LGG. Our findings may provide more precise management for LGGs and a useful reference for LLPS mechanism to link LGG studies.

MR Imaging of Pediatric Low-Grade Gliomas: Pretherapeutic Differentiation of BRAF V600E Mutation, BRAF Fusion, and Wild-Type Tumors in Patients without Neurofibromatosis-1

BACKGROUND AND PURPOSE

The prognosis and treatment of pediatric low-grade gliomas is influenced by their molecular subtype. MR imaging remains the mainstay for initial work-up and surgical planning. We aimed to determine the relationship between imaging patterns and molecular subtypes of pediatric low-grade gliomas.

MATERIALS AND METHODS

This was a retrospective bi-institutional study for patients diagnosed from 2004 to 2021 with pathologically confirmed pediatric low-grade gliomas molecularly defined as BRAF fusion, BRAF V600E mutant, or wild-type (which is neither BRAF V600E mutant nor BRAF fusion). Two neuroradiologists, blinded, independently reviewed imaging parameters from diagnostic MRIs, and discrepancies were resolved by consensus. Bivariate analysis was used followed by pair-wise comparison of the Dwass-Steel-Critchlow-Fligner method to compare the 3 molecular subtypes. Interreader agreement was assessed using κ.

RESULTS

We included 70 patients: 30 BRAF fusion, 19 BRAF V600E mutant, and 21 wild-type. There was substantial agreement between the readers for overall imaging variables (κ = 0.75). BRAF fusion tumors compared with BRAF V600E and wild-type tumors were larger (P = .0022), and had a greater mass effect (P = .0053), increased frequency of hydrocephalus (P = .0002), and diffuse enhancement (p <.0001). BRAF V600E mutant tumors were more often hemispheric (P < .0001), appeared more infiltrative (P = .0002), and, though infrequent, were the only group demonstrating diffusion restriction (qualitatively; P = .0042) with a lower ADC ratio (quantitatively) (P = .003).

CONCLUSIONS

BRAF fusion and BRAF V600E mutant pediatric low-grade gliomas have unique imaging features that can be used to differentiate them from each other and wild-type pediatric low-grade glioma using a standard radiology review with high interreader agreement. In the era of targeted therapy, these features can be useful for therapeutic planning before surgery.

The role of irinotecan-bevacizumab as rescue regimen in children with low-grade gliomas: a retrospective nationwide study in 72 patients

INTRODUCTION

At least half of children with low-grade glioma (LGG) treated with first line chemotherapy experience a relapse/progression and may therefore need a second-line chemotherapy. Irinotecan-bevacizumab has been recommended in this setting in France after encouraging results of pilot studies. We performed a retrospective analysis to define the efficacy, toxicity and predictors for response to the combination on a larger cohort.

METHODS

We reviewed the files from children < 19 years of age with progressive or refractory LGG treated between 2009 and 2016 in 7 French centers with this combination.

RESULTS

72 patients (median age 7.8 years [range 1-19]) received a median of 16 courses (range 3-30). The median duration of treatment was 9 months (range 1.4-16.2). 96% of patients experienced at least disease stabilization. The 6-month and 2-year progression-free survivals (PFS) were 91.7% [IC 95% 85.5-98.3] and 38.2% [IC 95% 28.2-51.8] respectively. No progression occurred after treatment in 18 patients with a median follow-up of 35.6 months (range 7.6-75.9 months). Younger patients had a worse PFS (p = 0.005). Prior chemoresistance, NF1 status, duration of treatment, histopathology or radiologic response did not predict response. The most frequent toxicities related to bevacizumab included grades 1-2 proteinuria in 21, epistaxis in 10, fatigue in 12 and hypertension in 8 while gastro-intestinal toxicity was the most frequent side effect related to irinotecan.

CONCLUSIONS

Bevacizumab-irinotecan has the potential of disease control clinically and radiographically in children with recurrent LGG whatever their previous characteristics; in many cases however these responses are not sustained, especially in younger children.

Pharmacological Approaches in Neurofibromatosis Type 1-Associated Nervous System Tumors

Simple Summary

Neurofibromatosis type 1 (NF1) is a common cancer predisposition genetic disease that is associated with significant morbidity and mortality. In this literature review, we discuss the major pathways in the nervous system that are affected by NF1, tumors that are associated with NF1, drugs that target these pathways, and genetic models of NF1. We also summarize the latest updates from clinical trials that are evaluating pharmacological agents to treat these tumors and discuss the efforts that are being made to cure the disease in the future

Abstract

Neurofibromatosis type 1 is an autosomal dominant genetic disease and a common tumor predisposition syndrome that affects 1 in 3000 to 4000 patients in the USA. Although studies have been conducted to better understand and manage this disease, the underlying pathogenesis of neurofibromatosis type 1 has not been completely elucidated, and this disease is still associated with significant morbidity and mortality. Treatment options are limited to surgery with chemotherapy for tumors in cases of malignant transformation. In this review, we summarize the advances in the development of targeted pharmacological interventions for neurofibromatosis type 1 and related conditions.

Quantitative MRI demonstrates abnormalities of the third ventricle subventricular zone in neurofibromatosis type-1 and sporadic paediatric optic pathway glioma

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MRI provides supporting evidence of third ventricle subventricular involvement in OPG.

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Third ventricle subventricular zone ADC and CBF differs between NF1 and sporadic OPG.

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Third ventricle subventricular zone ADC correlates with vision in sporadic OPG.

Background

The subventricular zone of the third ventricle (TVZ) is a germinal stem cell niche, identified as the possible location of optic pathway glioma (OPG) cell origin. Paediatric OPGs are predominantly diagnosed as low-grade astrocytomas, which are either sporadic or are associated with neurofibromatosis type-1 (NF1). These tumours often cause a significant impairment to visual acuity (VA). Infiltrative/invasive tumour activity is associated with increased apparent diffusion coefficient (ADC) and cerebral blood flow (CBF). This study aimed to determine whether TVZ imaging features differed between sporadic-OPG, NF1-OPG and controls, and whether the ADC and CBF profile at the germinal stem cell niche (the TVZ) correlated with the primary outcome of VA.

Methods

ADC and CBF MRI data were acquired from 30 paediatric OPG patients (median age 6 years; range 8 months–17 years), along with VA measurements, during clinical surveillance of their tumour. Values for mean ADC and maximum CBF were measured at the TVZ, and normalized to normal-appearing grey matter. These values were compared between the two OPG groups and the healthy control subjects, and multivariate linear regression was used to test the linear association between these values and patient’s VA.

Results

In the TVZ, normalized mean ADC was higher in NF1-associated OPG patients (N = 15), compared to both sporadic OPG patients (N = 15; p = 0.010) and healthy controls (N = 14; p < 0.001). In the same region, normalized maximum CBF was higher in sporadic OPG patients compared to both NF1-OPG patients (p = 0.016) and healthy controls (p < 0.001). In sporadic OPG patients only, normalized mean ADC in the TVZ was significantly correlated with visual acuity (R² = 0.41, p = 0.019). No significant correlations were found between TVZ CBF and ADC values and visual acuity in the NF1-associated OPG patients.

Conclusion

Quantitative MRI detects TVZ abnormalities in both sporadic and NF1-OPG patients, and identifies TVZ features that differentiate the two. TVZ features may be useful MRI markers of interest in future predictive studies involving sporadic OPG.

Phase I study of vinblastine in combination with nilotinib in children, adolescents, and young adults with refractory or recurrent low-grade glioma

Background

New rescue regimens are needed for pediatric refractory/recurrent low-grade glioma. Nilotinib is a tyrosine kinase inhibitor that has potential synergistic effects with vinblastine on angiogenesis, tumor cell growth, and immunomodulation.

Methods

This phase I trial aimed to determine the recommended doses of this combination for phase II trials (RP2D) using the dual-agent Bayesian continual reassessment method. Nilotinib was given orally twice daily (BID) in combination with once-weekly vinblastine injections for a maximum of 12 cycles of 28 days (clinicaltrials.gov, NCT01884922).

Results

Thirty-five pediatric patients were enrolled across 4 dose levels. The median age was 7 years and 10 had neurofibromatosis type 1. Patients had received a median of 3 prior treatment lines and 25% had received more than 4 previous treatment lines. Dose-limiting toxicity (DLT) during cycle 1 was hematologic, dermatologic, and cardiovascular. The RP2D was identified at 3 mg/m² weekly for vinblastine with 230 mg/m² BID for nilotinib (estimated probability of DLT = 18%; 95% credibility interval, 7-29%). Fifteen patients completed the 12 cycles; 2 stopped therapy prematurely due to toxicity and 18 due to disease progression. Three patients achieved a partial response leading to an objective response rate of 8.8% (95% confidence interval [CI], 1.9-23.7), and the disease control rate was 85.3% (95% CI, 68.9-95.1). The 12-month progression-free survival was 37.1% (95% CI, 23.2-53.67).

Conclusions

Vinblastine and nilotinib combination was mostly limited by myelosuppression and dermatologic toxicity. The efficacy of the combination at the RP2D is currently evaluated in a randomized phase II trial comparing this regimen to vinblastine alone.

Current treatment of optic nerve gliomas

PURPOSE OF REVIEW

Optic pathway gliomas are low-grade neoplasms that affect the precortical visual pathway of children and adolescents. They can affect the optic nerve, optic chiasm, optic tracts and radiations and can either be sporadic or associated with neurofibromatosis type one. Gliomas isolated to the optic nerve (ONG) represent a subgroup of optic pathway gliomas, and their treatment remains controversial. New developments in ONG treatment have emerged in recent years, and it is necessary for clinicians to have a current understanding of available therapies.

RECENT FINDINGS

The current review of the literature covers the background of and recent developments in ONG treatment, with a focus on standard chemotherapy, new molecularly targeted therapies, radiation therapy and surgical resection and debulking.

SUMMARY

Although standard chemotherapy remains the mainstay of ONG treatment, newer molecularly targeted therapies such as mitogen-activated protein kinase kinase inhibitors and bevacizumab represent a promising new treatment modality, and clinical studies are ongoing.

Prognostic role of microvessel density in patients with glioma

BACKGROUND

The aim of this study was to systematically evaluate the prognostic role of microvessel density (MVD) in patients with glioma through performing a meta-analysis.

METHODS

Web of Science, EMBASE, PubMed, Cochrane Library, and China National Knowledge Infrastructure were searched for potentially relevant literature. The study characteristics and relevant data were extracted. Hazard ratios (HRs) with 95% confidence intervals (CIs) were pooled to estimate the prognostic role of MVD in patients with glioma.

RESULTS

Nine studies with 536 patients were included. The pooled HR of higher MVD for overall survival (OS) was 1.64 (95% CI, 1.07-2.50) in patients with glioma. Subgroup analyses were also performed. The pooled HRs of higher MVD in studies from East Asia studies examining high-grade gliomas and studies using anti-CD105 antibodies were 1.99 (95% CI, 1.04-3.80), 1.60 (95% CI, 1.09-2.34) and 2.99 (95% CI, 1.50-5.99), respectively. No significant publication bias was found (P = .592), but significant between-study heterogeneity was observed (I = 80.5%, P <.001) in the meta-analysis.

CONCLUSION

Our results suggested that higher MVD was associated with worse OS in patients with glioma. The findings may assist future research on antiangiogenic therapy and help predict prognosis in glioma. However, due to the limited number of studies, more well-designed studies are warranted to further verify our results.

Use of bevacizumab as a single agent or in adjunct with traditional chemotherapy regimens in children with unresectable or progressive low-grade glioma

In pediatric low‐grade gliomas not amenable to complete resection, various chemotherapy regimens are the mainstream of treatment. An excellent overall survival of these patients makes justification of the intensification of chemotherapy difficult and calls for the development of new strategies. Bevacizumab, a humanized monoclonal antibody directed against Vascular endothelial growth factor (VEGF), has been successfully used in combination with irinotecan in a number of adult and pediatric studies and reports. Fifteen patients at median age of 7 years old (range 3 months to 15 years) were treated with bevacizumab in combination with conventional low‐toxicity chemotherapy. The majority had chiasmatic/hypothalamic and midline tumors, seven had confirmed BRAF pathway alterations including neurofibromatosis type 1 (2). Fourteen patients had more than one progression and three had radiotherapy. No deaths were documented, PFS at 11 and 15 months was 71.5% ± 13.9% and 44.7% ± 17.6% respectively. At the end of follow‐up 40% of patients has radiologically stable disease, three patients progressed shortly after completion of bevacizumab and two showed mixed response with progression of cystic component. Rapid visual improvement was seen in 6/8 patients, resolution of endocrine symptoms in 2/4 and motor function improvement in 4/6. No relation between histology or BRAF status and treatment response was observed. Treatment‐limiting toxicities included grade 4 proteinuria (2) and hypertension (2) managed with cessation (1) and pausing of therapy plus antihypertensives (1). In conclusion, bevacizumab is well tolerated and appears most effective for rapid tumor control to preserve vision and improve morbidity.

Feasibility Analysis for Treatment of Giant Intracranial Benign Tumor by Delayed Operation in Infancy

OBJECTIVE

The survival rate and prognosis in infants with giant intracranial tumors are significantly worse than in older children. This study aimed to analyze the feasibility of delayed operation for infants with giant intracranial benign tumor by evaluating the initial clinical presentations, expectant treatment measures, perioperative vital signs, and recuperation after surgery.

PATIENTS AND DATA

We reviewed 3 infant patients (average age, 9.33 months; range, 5-12 months) with giant intracranial benign tumors during January 2015 and April 2016. The maximum sections of tumors were 38 × 50 mm, 57 × 39 mm, and 55 × 67 mm, respectively. All clinical presentations, neuroimaging, and laboratory examinations were recorded.

RESULTS

Obstructive hydrocephalus was observed in 2 infants; ventriculoperitoneal shunts were placed in both before the delayed tumor resection. The disease progressed rapidly in the infant with teratoma and surgery was performed 4 months after placement of the ventriculoperitoneal shunt. The other 2 patients had experienced a 12-month growth and developmental phase and later underwent operations. Gross total resection was achieved in all patients. The pathologic results were consistent with the preoperative diagnosis. During a period of high-quality postoperative care, they remained stable and were discharged without any complications or neurologic deficits, and continued to improve toward their baseline.

CONCLUSIONS

Delayed operation enabled infant patients to gain a better physical state, with a stage of full preoperative preparation that may reduce intraoperative/postoperative morbidity and mortality.

Phase II study of sorafenib in children with recurrent or progressive low-grade astrocytomas

BACKGROUND

Activation of the RAS-RAF-MEK-ERK signaling pathway is thought to be the key driver of pediatric low-grade astrocytoma (PLGA) growth. Sorafenib is a multikinase inhibitor targeting BRAF, VEGFR, PDGFR, and c-kit. This multicenter phase II study was conducted to determine the response rate to sorafenib in patients with recurrent or progressive PLGA.

METHODS

Key eligibility criteria included age ≥ 2 years, progressive PLGA evaluable on MRI, and at least one prior chemotherapy treatment. Sorafenib was administered twice daily at 200 mg/m(2)/dose (maximum of 400 mg/dose) in continuous 28-day cycles. MRI, including 3-dimensional volumetric tumor analysis, was performed every 12 weeks. BRAF molecular testing was performed on tumor tissue when available.

RESULTS

Eleven patients, including 3 with neurofibromatosis type 1 (NF1), were evaluable for response; 5 tested positive for BRAF duplication. Nine patients (82%) came off trial due to radiological tumor progression after 2 or 3 cycles, including 3 patients with confirmed BRAF duplication. Median time to progression was 2.8 months (95% CI, 2.1-31.0 months). Enrollment was terminated early due to this rapid and unexpectedly high progression rate. Tumor tissue obtained from 4 patients after termination of the study showed viable pilocytic or pilomyxoid astrocytoma.

CONCLUSIONS

Sorafenib produced unexpected and unprecedented acceleration of tumor growth in children with PLGA, irrespective of NF1 or tumor BRAF status. In vitro studies with sorafenib indicate that this effect is likely related to paradoxical ERK activation. Close monitoring for early tumor progression should be included in trials of novel agents that modulate signal transduction.

Angiogenesis and angiogenic tyrosine kinase receptor expression in pediatric brain tumors

Tumor angiogenesis and receptor tyrosine kinases (RTK) are major novel targets in anticancer molecular therapy. Accordingly, we characterized the vascular network and the expression pattern of angiogenic RTK in the most frequent pediatric brain tumors. In a retrospective collection of 44 cases (14 astrocytoma, 16 ependymoma and 14 medulloblastoma), immunohistochemistry for VEGFR1, VEGFR2, PDGFRα, PDGFRβ, and c-Kit as well as microvessel labeling with CD34 and SMA were conducted on surgical specimens. We found a significantly higher vascular density in ependymoma. Glomeruloid formations were abundant in medulloblastoma but rare or almost absent in astrocytoma and ependymoma, respectively. C-Kit and VEGFR2 labeled blood vessels were more abundant in ependymoma than in the other two types of tumors. In contrast, medulloblastoma contained higher number of PDGFRα expressing vessels. In tumor cells, we found no VEGFR2 but VEGFR1 expression in all three tumor types. PDGFRα was strongly expressed on the tumor cells in all three malignancies, while PDGFRβ tumor cell expression was present in the majority of medulloblastoma cases. Interestingly, small populations of c-Kit expressing cancer cells were found in a number of medulloblastoma and ependymoma cases. Our study suggests that different angiogenic mechanisms are present in ependymoma and medulloblastoma. Furthermore ependymoma patients may benefit from anti-angiogenic therapies based on the high vascularization as well as the endothelial expression of c-kit and VEGFR2. The expression pattern of the receptors on tumor cells also suggests the targeting of specific angiogenic tyrosine kinase receptors may have direct antitumor activity. Further preclinical and biomarker driven clinical investigations are needed to establish the application of tyrosine kinase inhibitors in the treatment of pediatric brain tumors.

New strategies in pediatric gliomas: molecular advances in pediatric low-grade gliomas as a model

Pediatric low-grade gliomas (pLGG) account for more brain tumors in children than any other histologic subtype. While surgery, chemotherapy and radiation remain the mainstay of upfront treatment, recent advances in molecular interrogation of pLGG have shown a small number of recurring genetic mutations in these tumors that might be exploited therapeutically. Notable findings include abnormalities in the RAS/MAP kinase pathway such as NF-1 loss or BRAF activation and mTOR activation. Recent identification of activating re-arrangements in c-MYB and MYBL1 in pediatric diffuse astrocytoma also provide candidates for therapeutic intervention. Targeting these molecularly identified pathways may allow for improved outcomes for patients as pediatric oncology moves into the era of biology-driven medicine.

Arterial spin-labeled perfusion of pediatric brain tumors

BACKGROUND AND PURPOSE

Pediatric brain tumors have diverse pathologic features, which poses diagnostic challenges. Although perfusion evaluation of adult tumors is well established, hemodynamic properties are not well characterized in children. Our goal was to apply arterial spin-labeling perfusion for various pathologic types of pediatric brain tumors and evaluate the role of arterial spin-labeling in the prediction of tumor grade.

MATERIALS AND METHODS

Arterial spin-labeling perfusion of 54 children (mean age, 7.5 years; 33 boys and 21 girls) with treatment-naive brain tumors was retrospectively evaluated. The 3D pseudocontinuous spin-echo arterial spin-labeling technique was acquired at 3T MR imaging. Maximal relative tumor blood flow was obtained by use of the ROI method and was compared with tumor histologic features and grade.

RESULTS

Tumors consisted of astrocytic (20), embryonal (11), ependymal (3), mixed neuronal-glial (8), choroid plexus (5), craniopharyngioma (4), and other pathologic types (3). The maximal relative tumor blood flow of high-grade tumors (grades III and IV) was significantly higher than that of low-grade tumors (grades I and II) (P < .001). There was a wider relative tumor blood flow range among high-grade tumors (2.14 ± 1.78) compared with low-grade tumors (0.60 ± 0.29) (P < .001). Across the cohort, relative tumor blood flow did not distinguish individual histology; however, among posterior fossa tumors, relative tumor blood flow was significantly higher for medulloblastoma compared with pilocytic astrocytoma (P = .014).

CONCLUSIONS

Characteristic arterial spin-labeling perfusion patterns were seen among diverse pathologic types of brain tumors in children. Arterial spin-labeling perfusion can be used to distinguish high-grade and low-grade tumors.

Optic pathway gliomas: a review

Optic pathway gliomas account for 3-5% of all pediatric CNS tumors and represent the most common intrinsic optic nerve tumors. These tumors occur preferentially during the first decade of life and are particularly frequent in children with neurofibromatosis type 1. Although optic pathway gliomas are low-grade tumors, their behavior can be aggressive, and their management is often challenging. Their management includes observation, surgery, chemotherapy and radiation. The role of each modality is discussed as well as current and future developments in treatment, in particular targeted therapies that are currently being investigated.

Optic pathway gliomas in adolescence--time to challenge treatment choices?

BACKGROUND

Optimal management of optic pathway/hypothalamic glioma (OPHG) remains an ongoing challenge. Little is known about the natural history, management strategies, and outcomes in adolescents. Carboplatin-based chemotherapy is a useful modality in younger children, delaying radiation to their immature brains. National trials have focused on younger children and excluded adolescents from studies evaluating the role of chemotherapy.

METHODS

This retrospective study describes clinical characteristics, treatment regimens, and outcomes in adolescents (aged ≥ 10 years) with OPHG (diagnosis during 1990-2006). Progression-free survival was compared with that in a cohort of younger children (aged <10 years).

RESULTS

Thirty-three adolescents (19 females, 6 with neurofibromatosis type 1) with OPHG were identified within 2 Canadian pediatric oncology institutions. The majority presented with visual symptoms (82%). More than 55% (18 of 33) involved the posterior tract and/or hypothalamus (modified Dodge classification 3/4). Seventeen were initially observed; 8 remained progression free. Of the 25 of 33 adolescents who required active treatment, 9 (36%) needed second-line therapy. The progression-free survival for any first active treatment at age <10 years (52 of 102) or ≥ 10 years (25 of 33) was similar (46.9 vs 46.8 months; P = .60). In those who received chemotherapy as first-line treatment or after prior nonchemotherapy treatment failure, the progression-free survival trend was superior (62.9 vs 38.9 months) in those aged ≥ 10 years although not statistically significant (P = .16).

CONCLUSIONS

Chemotherapy is a valuable treatment modality for the achievement of disease control even in adolescents; their progression-free survival compares favorably with that in younger children. We propose that chemotherapy be considered as a first-line modality in adolescents, avoiding potential radiation-associated morbidities.

Analysis of EGF+61A>G polymorphism and EGF serum levels in Brazilian glioma patients treated with perillyl alcohol-based therapy

PURPOSE

Malignant gliomas are associated with alteration in EGF/EGFR signaling. Functional EGF+61A>G polymorphism is implicated with risk, recurrence, and progression of glioma. This study aimed to establish a putative association of EGF+61A>G with risk of glioma development, production of angiogenic growth factor EGF, and the response to perillyl alcohol administered by intranasal route.

METHODS

The study included 83 patients with recurrent glioma enrolled in Phase I/II trial for intranasal perillyl alcohol therapy and subjects without cancer (n = 196) as control group. DNA was extracted from blood samples, EGF genotype performed with PCR-RFLP assay, and EGF circulating levels by enzyme immunoassay. Adequate statistical tests were performed to verify associations between polymorphism and glioma risk, and genotype correlation with EGF circulating levels. The log-rank test was also used to evaluate differences on patient survival.

RESULTS

Patients with primary glioblastoma had high frequency of AA genotype (p = 0.037) and A allele (p = 0.037). Increased EGF circulating levels were observed in glioma patients with AA (p = 0.042), AG (p = 0.006), and AA + AG (p = 0.008) genotypes compared with GG. Patients with GG genotype showed increased but not significant (p > 0.05) survival rate, and EGF levels lower than 250 pg/mL was consistently (p = 0.0374) associated with increased survival.

CONCLUSION

Presence of EGF+61A>G polymorphism in Brazilian subjects was associated with glioma risk and increased circulating EGF levels. Better response to perillyl alcohol-based therapy was observed in a group of adult Brazilian subjects with lower EGF levels.

Proliferative and metabolic markers in incompletely excised pediatric pilocytic astrocytomas--an assessment of 3 new variables in predicting clinical outcome

Although pilocytic astrocytoma (PA) is the most common brain tumor diagnosed in children, few prognostic variables have been delineated that stratify the risk of clinical progression in patients with this tumor. In this study, the MIB-1 labeling index was compared with 2 other immunohistochemical markers of cell proliferation, phospho-histone H3 (PHH3) and mini-chromosomal maintenance protein 2 (MCM2) in 80 incompletely resected PAs to see which was best able to identify patients at risk for tumor progression. 0(6)-Methylguanine-DNA methyltransferase (MGMT) protein expression, which has been predictive of progression-free survival (PFS) in high-grade gliomas in children, was also evaluated in these cases. The mean follow-up period was 7.81 ± 3.9 years, and 42.8% of tumors have shown progression at the time of censoring. A MIB-1 labeling index ≥2.0 was associated with shortened PFS as a grouped variable by log-ranked analysis (P = .03) and by Cox regression analysis as a continuous variable (P = .007). None of the other potential biomarkers was significantly predictive of PFS. Although the amount of MCM2 staining correlated with the MIB-1 labeling index (P < .001), MCM2 reactivity was not independently associated with outcome. We conclude that MIB-1 labeling remains the best predictor of PFS in pediatric PAs.

Bevacizumab in recurrent high-grade pediatric gliomas

Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, has shown promise in treating recurrent adult high-grade glioma (HGG). However, there is very little data on recurrent or progressive pediatric HGG treated with bevacizumab. We report the results of a single institution experience using bevacizumab and irinotecan in children who relapsed or progressed following standard therapy. Twelve pediatric patients with recurrent or progressive HGG received bevacizumab at 10 mg/kg every 2 weeks with irinotecan at 125 mg/m(2). Magnetic resonance imaging (MRI) was performed prior to therapy and every 8 weeks subsequently. Ten patients had supratentorial HGG; 2 had DIPG. Radiological responses were defined according to MacDonald's criteria. Progression-free survival (PFS), overall survival (OS), and toxicities were analyzed. Ten (83.3%) patients tolerated bevacizumab without serious toxicity. Therapy was discontinued in 1 patient because of anaphylaxis. Another patient developed grade III delayed wound healing and deep vein thrombosis. Two patients (16.7%) experienced a partial response after the first MRI. No complete radiographic responses were seen. Stable disease was noted in 4 (33.3%) patients. The median PFS and OS were 2.25 and 6.25 months, respectively. A diffuse invasive recurrence pattern was noted in 5 (45.5%) patients. Treatment tolerance, toxicity, and recurrence profiles were comparable to adult HGG patients treated with bevacizumab. However, the radiological response rate, response duration, and survival appeared inferior in pediatric patients. Genetic differences in pediatric gliomas might account for this difference.

Expression and clinical significance of EGFL7 in malignant glioma

PURPOSE

Tumor angiogenesis is an important factor for the continuous growth of human malignancies and can be used to predict the prognosis for patients. In the current study, we examined the expression of EGF-like domain 7 (EGFL7), an endothelial cell-derived secreted factor, in malignant gliomas and explored its clinical significance.

METHODS

We determined the steady-state mRNA levels of EGFL7 from 36 fresh glioma samples by semi-quantitative RT-PCR and the protein levels from 45 paraffin-embedded glioma samples by immunohistochemistry, respectively. Normal brain tissues from 10 patients with brain trauma were used as control. We also analyzed the correlations between the expression levels of EGFL7 and various clinical parameters, including patient gender, age, tumor grade, tumor proliferation marker Ki-67, and microvessel density (MVD).

RESULTS

We found that EGFL7 was not detectable in normal brain tissues, but was up-regulated in both tumor cells and vascular endothelial cells within malignant glioma. The expression level of EGFL7 in malignant glioma significantly correlated with the tumor grade, Ki-67 expression and MVD (P < 0.01).

CONCLUSIONS

Our data suggest that EGFL7 expression is a novel predictive factor for the clinical progression of malignant glioma, and may constitute a therapeutic target for anti-angiogenesis therapy in patients with the disease.

Pediatric low-grade gliomas

Pediatric low-grade gliomas encompass a heterogeneous set of tumors of different histologies. Cerebellar pilocytic astrocytomas occur most frequently followed by supratentorial diffuse fibrillary astrocytomas. Recent research has implicated activation of the RAS/RAF/MEK pathway in tumorigenesis of these tumors. Surgery is the mainstay of therapy. Overall survival rates for patients whose tumors are completely resected are 90% or greater, 10 years from diagnosis. Conversely, most optic pathway/hypothalamic, deep midline, and brain stem gliomas have minimal potential for resection; these tumors can be difficult to treat and deserve special attention. Combination chemotherapy is currently recommended as front-line adjuvant treatment for progressive or recurrent tumors. Second-line radiotherapy can also improve overall survival but is associated with more frequent and significant neurocognitive, endocrine, and other long-term toxicities.

Multiparameter computational modeling of tumor invasion

Clinical outcome prognostication in oncology is a guiding principle in therapeutic choice. A wealth of qualitative empirical evidence links disease progression with tumor morphology, histopathology, invasion, and associated molecular phenomena. However, the quantitative contribution of each of the known parameters in this progression remains elusive. Mathematical modeling can provide the capability to quantify the connection between variables governing growth, prognosis, and treatment outcome. By quantifying the link between the tumor boundary morphology and the invasive phenotype, this work provides a quantitative tool for the study of tumor progression and diagnostic/prognostic applications. This establishes a framework for monitoring system perturbation towards development of therapeutic strategies and correlation to clinical outcome for prognosis.

Pediatric low-grade gliomas and the need for new options for therapy: Why and how?

Pediatric low-grade gliomas are the most common tumors of the central nervous system in children, accounting for almost 50% of all childhood brain tumors. They are a heterogeneous group of tumors with different histologic subtypes. Most treatment studies address low-grade gliomas as a single entity, depriving us of histology-specific treatment outcomes. This is mostly due to a lack of understanding of tumor biology at the molecular level. Pediatric low-grade gliomas are not benign, and most incompletely resected tumors will progress and negatively affect quality of life. The advancements made in understanding sporadic pilocytic astrocytoma and neurofibromatosis 1-associated pilocytic astrocytoma in particular have paved the way for potential targeted therapy and biological stratification. Such progress in pilocytic astrocytoma needs to be consolidated and expanded to other histologic varieties of pediatric low-grade gliomas.

Microvascular maturity elicited in tissue treated with cytokine-loaded hyaluronan-based hydrogels

Hydrogels composed of crosslinked, chemically modified hyaluronic acid (HA), gelatin (Gtn) and heparin (Hp) were preloaded with vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1), keratinocyte growth factor (KGF) or platelet derived growth factor (PDGF) either individually or in combination with VEGF and implanted into the Balb/c mouse ear pinna. At 7 and 14 days post-surgery, elicited vascular maturity levels were quantified using immunohistochemical (IHC) staining techniques and reported as a vascular maturity index (VMI). At both time points, it was discovered that the dual cytokine combinations elicited greater maturity levels than that of cytokine administered individually. For example, VEGF and KGF-containing HA:Hp implants at day 7 yielded VMI values of -0.1375 and -0.092, respectively, whereas their combination resulted in a VMI of 0.176 (p<0.007). At day 7, only one of the seven HA:Hp experimental cases yielded a positive VMI (VEGF+KGF), whereas four of the seven HA:Hp cases yielded positive VMI values at day 14, indicating a sustained maturity response. The same general trends were found to exist in tissue treated with HA:Hp:Gtn experimental implants. Differences in elicited maturity also existed between tissue treated with HA:Hp and HA-containing hydrogels (VMI=0.176 for HA:Hp-VEGF+KGF vs. -0.064 for HA-VEGF+KGF, p<0.012), and these differences are thought to result from differences in characteristic cytokine release rates. This result also suggests that the presentation of multiple growth factors (GFs) on immobilized Hp may actively contribute to cytokine related signal transduction, a characteristic that may be exploited in the future to improve the efficacy of cytokine-loaded implants towards tissue regeneration therapeutic strategies.

Computer simulation of glioma growth and morphology

Despite major advances in the study of glioma, the quantitative links between intra-tumor molecular/cellular properties, clinically observable properties such as morphology, and critical tumor behaviors such as growth and invasiveness remain unclear, hampering more effective coupling of tumor physical characteristics with implications for prognosis and therapy. Although molecular biology, histopathology, and radiological imaging are employed in this endeavor, studies are severely challenged by the multitude of different physical scales involved in tumor growth, i.e., from molecular nanoscale to cell microscale and finally to tissue centimeter scale. Consequently, it is often difficult to determine the underlying dynamics across dimensions. New techniques are needed to tackle these issues. Here, we address this multi-scalar problem by employing a novel predictive three-dimensional mathematical and computational model based on first-principle equations (conservation laws of physics) that describe mathematically the diffusion of cell substrates and other processes determining tumor mass growth and invasion. The model uses conserved variables to represent known determinants of glioma behavior, e.g., cell density and oxygen concentration, as well as biological functional relationships and parameters linking phenomena at different scales whose specific forms and values are hypothesized and calculated based on in vitro and in vivo experiments and from histopathology of tissue specimens from human gliomas. This model enables correlation of glioma morphology to tumor growth by quantifying interdependence of tumor mass on the microenvironment (e.g., hypoxia, tissue disruption) and on the cellular phenotypes (e.g., mitosis and apoptosis rates, cell adhesion strength). Once functional relationships between variables and associated parameter values have been informed, e.g., from histopathology or intra-operative analysis, this model can be used for disease diagnosis/prognosis, hypothesis testing, and to guide surgery and therapy. In particular, this tool identifies and quantifies the effects of vascularization and other cell-scale glioma morphological characteristics as predictors of tumor-scale growth and invasion.