A feasibility and efficacy study of rapamycin and erlotinib for recurrent pediatric low-grade glioma (LGG)

Signaling pathways in brain tumors and therapeutic interventions

Brain tumors, although rare, contribute to distinct mortality and morbidity at all ages. Although there are few therapeutic options for brain tumors, enhanced biological understanding and unexampled innovations in targeted therapies and immunotherapies have considerably improved patients' prognoses. Nonetheless, the reduced response rates and unavoidable drug resistance of currently available treatment approaches have become a barrier to further improvement in brain tumor (glioma, meningioma, CNS germ cell tumors, and CNS lymphoma) treatment. Previous literature data revealed that several different signaling pathways are dysregulated in brain tumor. Importantly, a better understanding of targeting signaling pathways that influences malignant behavior of brain tumor cells might open the way for the development of novel targeted therapies. Thus, there is an urgent need for a more comprehensive understanding of the pathogenesis of these brain tumors, which might result in greater progress in therapeutic approaches. This paper began with a brief description of the epidemiology, incidence, risk factors, as well as survival of brain tumors. Next, the major signaling pathways underlying these brain tumors' pathogenesis and current progress in therapies, including clinical trials, targeted therapies, immunotherapies, and system therapies, have been systemically reviewed and discussed. Finally, future perspective and challenges of development of novel therapeutic strategies in brain tumor were emphasized.

Bortezomib advanced mechanisms of action in multiple myeloma, solid and liquid tumors along with its novel therapeutic applications

Bortezomib (BTZ) is a first-in-class reversible and selective proteasome inhibitor. It inhibits the ubiquitin proteasome pathway that leads to the degradation of many intracellular proteins. Initially, BTZ was FDA approved for the treatment of refractory or relapsed multiple myeloma (MM) in 2003. Later, its usage was approved for patients with previously untreated MM. In 2006, BTZ was approved for the treatment of relapsed or refractory Mantle Cell Lymphoma (MCL) and, in 2014, for previously untreated MCL. BTZ has been extensively studied either alone or in combination with other drugs for the treatment of different liquid tumors especially in MM. However, limited data evaluated the efficacy and safety of using BTZ in patients with solid tumors. In this review, we will discuss the advanced and novel mechanisms of action of BTZ documented in MM, solid tumors and liquid tumors. Moreover, we will shed the light on the newly discovered pharmacological effects of BTZ in other prevalent diseases.

Glioma targeted therapy: insight into future of molecular approaches

Gliomas are the common type of brain tumors originating from glial cells. Epidemiologically, gliomas occur among all ages, more often seen in adults, which males are more susceptible than females. According to the fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5), standard of care and prognosis of gliomas can be dramatically different. Generally, circumscribed gliomas are usually benign and recommended to early complete resection, with chemotherapy if necessary. Diffuse gliomas and other high-grade gliomas according to their molecule subtype are slightly intractable, with necessity of chemotherapy. However, for glioblastoma, feasible resection followed by radiotherapy plus temozolomide chemotherapy define the current standard of care. Here, we discuss novel feasible or potential targets for treatment of gliomas, especially IDH-wild type glioblastoma. Classic targets such as the p53 and retinoblastoma (RB) pathway and epidermal growth factor receptor (EGFR) gene alteration have met failure due to complex regulatory network. There is ever-increasing interest in immunotherapy (immune checkpoint molecule, tumor associated macrophage, dendritic cell vaccine, CAR-T), tumor microenvironment, and combination of several efficacious methods. With many targeted therapy options emerging, biomarkers guiding the prescription of a particular targeted therapy are also attractive. More pre-clinical and clinical trials are urgently needed to explore and evaluate the feasibility of targeted therapy with the corresponding biomarkers for effective personalized treatment options.

Implications of new understandings of gliomas in children and adults with NF1: report of a consensus conference

Gliomas are the most common primary central nervous system tumors occurring in children and adults with neurofibromatosis type 1 (NF1). Over the past decade, discoveries of the molecular basis of low-grade gliomas (LGGs) have led to new approaches for diagnosis and treatments. However, these new understandings have not been fully applied to the management of NF1-associated gliomas. A consensus panel consisting of experts in NF1 and gliomas was convened to review the current molecular knowledge of NF1-associated low-grade “transformed” and high-grade gliomas; insights gained from mouse models of NF1-LGGs; challenges in diagnosing and treating older patients with NF1-associated gliomas; and advances in molecularly targeted treatment and potential immunologic treatment of these tumors. Next steps are recommended to advance the management and outcomes for NF1-associated gliomas.

NVP-BEZ235 or JAKi Treatment leads to decreased survival of examined GBM and BBC cells

Cancer cells almost universally harbor constitutively active Phosphatidylinositol-3 Kinase (PI3K) Pathway activity via mutation of key signaling components and/or epigenetic mechanisms. Scores of PI3K Pathway inhibitors are currently under investigation as putative chemotherapeutics. However, feedback and stem cell mechanisms induced by PI3K Pathway inhibition can lead to reduced treatment efficacy. To address therapeutic barriers, we examined whether JAKi would reduce stem gene expression in a setting of PI3K Pathway inhibition in order to improve treatment efficacy. We targeted the PI3K Pathway with NVP-BEZ235 (dual PI3K and mTOR inhibitor) in combination with the Janus Kinase inhibitor JAKi in glioblastoma (GBM) and basal-like breast cancer (BBC) cell lines. We examined growth, gene expression, and apoptosis in cells treated with NVP-BEZ235 and/or JAKi. Growth and recovery assays showed no significant impact of dual treatment with NVP-BEZ235/JAKi compared to NVP-BEZ235 treatment alone. Gene expression and flow cytometry revealed that single and dual treatments induced apoptosis. Stem gene expression was retained in dual NVP-BEZ235/JAKi treatment samples. Future in vivo studies may give further insight into the impact of combined NVP-BEZ235/JAKi treatment in GBM and BBC.

Cutaneous reactions to pediatric cancer treatment part II: Targeted therapy

Cancer remains a leading cause of morbidity and mortality among children. Targeted therapies may improve survivorship; however, unique side-effect profiles have also emerged with these novel therapies. Changes in hair, skin, and nails-termed dermatologic adverse events (AEs)-are among the most common sequelae and may result in interruption or discontinuation of therapy. Though dermatologic AEs have been detailed in adults, these findings are not well described in the pediatric population. We reviewed the literature to characterize dermatologic AEs to anticancer targeted therapies available as of July 2020 and summarized the spectrum of clinical findings as well as treatment recommendations for children. Dermatologic AEs are among the most common AEs reported in pediatric patients receiving targeted therapy, but morphologic and histologic descriptions are often lacking in current publications. Pediatric dermatologists are uniquely poised to recognize specific morphology of dermatologic AEs and make recommendations for prevention and treatment that may improve quality of life and enable ongoing cancer therapy.

Sustained response to erlotinib and rapamycin in a patient with pediatric anaplastic oligodendroglioma

One goal of precision medicine is to identify mutations within individual tumors to design targeted treatment approaches. This report details the use of genomic testing to select a targeted therapy regimen of erlotinib and rapamycin for a pediatric anaplastic oligodendroglioma refractory to standard treatment, achieving a 33-month sustained response. Immunohistochemical analysis of total and phosphorylated protein isoforms showed abnormal signaling consistent with detected mutations, while revealing heterogeneity in per-cell activation of signaling pathways in multiple subpopulations of tumor cells throughout the course of disease. This case highlights molecular features that may be relevant to designing future targeted treatments.

Management of Children with Optic Gliomas and Neurofibromatosis Type 1

Optic pathway gliomas (OPG) are a common cancer in children with neurofibromatosis type 1. OPGs can cause clinical symptoms such as reduction of visual acuity, alterations of the visual field, pallor of the optical papilla, strabismus, endocrinological alterations up to diencephalic syndrome.The current guidelines provide for wait and see as the main approach if the tumor is not causing visual deterioration and adopting treatment only in the event of significant impairment of the visual function. Therefore, it is essential to early detect the visual deterioration changes as well as the identification of children eligible for treatment.

Drug repurposing towards targeting cancer stem cells in pediatric brain tumors

In the pediatric population, brain tumors represent the most commonly diagnosed solid neoplasms and the leading cause of cancer-related deaths globally. They include low-grade gliomas (LGGs), medulloblastomas (MBs), and other embryonal, ependymal, and neuroectodermal tumors. The mainstay of treatment for most brain tumors includes surgical intervention, radiation therapy, and chemotherapy. However, resistance to conventional therapy is widespread, which contributes to the high mortality rates reported and lack of improvement in patient survival despite advancement in therapeutic research. This has been attributed to the presence of a subpopulation of cells, known as cancer stem cells (CSCs), which reside within the tumor bulk and maintain self-renewal and recurrence potential of the tumor. An emerging promising approach that enables identifying novel therapeutic strategies to target CSCs and overcome therapy resistance is drug repurposing or repositioning. This is based on using previously approved drugs with known pharmacokinetic and pharmacodynamic characteristics for indications other than their traditional ones, like cancer. In this review, we provide a synopsis of the drug repurposing methodologies that have been used in pediatric brain tumors, and we argue how this selective compilation of approaches, with a focus on CSC targeting, could elevate drug repurposing to the next level.

New treatment modalities in NF-related neuroglial tumors

The management of low-grade gliomas (LGGs) and other neuroglial tumors in children with neurofibromatosis type 1 (NF1) has not changed over the past 2-3 decades. With the widespread utilization of chemotherapy for younger children with progressive LGGs, outcomes have been good for most patients who have required treatment. However, some may progress after the initiation of chemotherapy and others, although radiographically responding or with stable disease, may develop progressive neurologic and visual deterioration. Molecular-targeted therapy has become an option for patients who have progressed after receiving chemotherapy and the mTOR inhibitors and bevacizumab have already shown some degree of efficacy. However, the greatest impact has been the introduction of the MEK inhibitors. A variety of different MEK inhibitors are in clinical trials and have already demonstrated the ability to result in radiographic tumor shrinkage in the majority of children with NF1 and progressive LGGs. Because of this efficacy, the MEK inhibitors have moved rapidly from phase I studies to ongoing phase III studies comparing their benefit directly to that of chemotherapy. The long-term ability of these agents to not only control disease, but improve visual and/or neurological function, as well as their short- and long-term safety, are open questions that can only be answered by well-constructed prospective, often randomized, clinical trials.

Neurofibromatosis 1-associated optic pathway gliomas

BACKGROUND

Optic Pathway Gliomas (OPG) are the most common brain tumor in Neurofibromatosis 1 patients (NF1). They are found along the optic pathway and may involve the optic nerves, chiasm, retro-chiasmatic structures, and the optic radiations. NF1 associate OPG (NF1-OPG) have variable presentation, disease course and response to treatment. The optimal management is patient-specific and should be tailored by a multidisciplinary team. Age, sex, histology, and molecular markers may be important factors in the individualized decision-making process. Chemotherapy is the first-line treatment in cases of progressive tumors, and visual preservation is the main goal of treatment.

PURPOSE

In this paper we will review the disease, practical management, and recent advances of NF1-OPG.

Associations of histological and molecular alterations with invasion of the corpus callosum in gliomas

BACKGROUND

Glioma invading the corpus callosum (CC) accounts for approximately 14% of gliomas and is thought to be more aggressive. However, there is still a lack of studies on the pathogenesis and molecular features of this condition. Here, we examined the occurrence association of CC invasion with respect to patients' clinical, pathological, and genetic characteristics.

METHODS

First, a cohort of 331 patients was included, with 86 cases (26%) that were diagnosed with invasion glioma. They were all analyzed for basic clinical and pathological characteristics and four routinely tested glioma molecular markers. Second, 29 pairs of patients who underwent deep sequencing of 68 glioma molecular alterations were selected from both groups for in-depth analysis.

RESULTS

The results of the first part showed that there was no difference between the two groups in terms of the basic factors in univariate analysis, while in multivariate logistic analysis, WHO grade was the risk factor for CC invasion (p = 0.001). The results of the second part showed that the paired groups had different genetic expression profiles, which highlighted glioma invading the CC as a distinct biological entity. PDGFRA mutation (PDGFRAmut) was present in 9 patients with invasive gliomas (31%), but only in one case (3.4%) in the control group (OR 17.331; 95% CI 1.987-151.156).

CONCLUSION

Our data revealed the clinical, pathological, and genetic characteristics of glioma invading the CC and showed that it may be associated with glioma WHO grade and PDGFRAmut, but not other factors. Thus, the risk signaling pathway may offer potential therapeutic targets for this disease.

Molecularly Targeted Agents in the Therapy of Pediatric Brain Tumors

Pediatric brain tumors are the leading cause of cancer-related death in children. Recent advances in sequencing techniques, and collaborative efforts to encode the mutational landscape of various tumor subtypes, have resulted in the identification of recurrent mutations that may present as actionable targets in these tumors. A number of molecularly targeted agents are approved or in development for the treatment of various tumor types in adult patients. Similarly, these agents are increasingly being incorporated into pediatric clinical trials, allowing for a targeted approach to treatment. However, due to the genetic heterogeneity of these tumors, focused clinical trials in pediatric patients are challenging and regulatory hurdles may delay access to therapeutic compounds that are in regular use in adult patients. The tumor site-agnostic clinical development of TRK inhibitors for pediatric solid tumors is a current example of how the combination of genetic testing and innovative clinical trial design can accelerate the clinical development of targeted agents for pediatric patients.

Molecular genetics and therapeutic targets of pediatric low-grade gliomas

Pediatric low-grade gliomas (PLGGs) have relatively favorable prognosis and some resectable PLGGs, such as cerebellar pilocytic astrocytoma, can be cured by surgery alone. However, many PLGG cases are unresectable and some of them undergo tumor progression. Therefore, a multidisciplinary approach is necessary to treat PLGG patients. Recent genomic analysis revealed a broad genomic landscape underlying PLGG. Notably, the majority of PLGGs present MAPK pathway-associated genomic alterations and MAPK signaling-dependent tumor progression. Following preclinical evidence, many clinical trials based on molecular target therapy have been conducted on PLGG patients, some of whom exhibited durable response to target therapy. Here, we provide an overview of PLGG genetics and the evidence supporting the application of molecular target therapy in these patients.

Insights into optic pathway glioma vision loss from mouse models of neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a common cancer predisposition syndrome caused by mutations in the NF1 gene. The NF1-encoded protein (neurofibromin) is an inhibitor of the oncoprotein RAS and controls cell growth and survival. Individuals with NF1 are prone to developing low-grade tumors of the optic nerves, chiasm, tracts, and radiations, termed optic pathway gliomas (OPGs), which can cause vision loss. A paucity of surgical tumor specimens and of patient-derived xenografts for investigative studies has limited our understanding of human NF1-associated OPG (NF1-OPG). However, mice genetically engineered to harbor Nf1 gene mutations develop optic gliomas that share many features of their human counterparts. These genetically engineered mouse (GEM) strains have provided important insights into the cellular and molecular determinants that underlie mouse Nf1 optic glioma development, maintenance, and associated vision loss, with relevance by extension to human NF1-OPG disease. Herein, we review our current understanding of NF1-OPG pathobiology and describe the mechanisms responsible for tumor initiation, growth, and associated vision loss in Nf1 GEM models. We also discuss how Nf1 GEM and other preclinical models can be deployed to identify and evaluate molecularly targeted therapies for OPG, particularly as they pertain to future strategies aimed at preventing or improving tumor-associated vision loss in children with NF1.

Neurofibromatosis type 1 and optic pathway glioma: Molecular interplay and therapeutic insights

Children with neurofibromatosis type 1 (NF1) are predisposed to develop central nervous system neoplasms, the most common of which are low-grade gliomas (LGGs). The absence of human NF1 associated LGG-derived cell lines, coupled with an inability to generate patient-derived xenograft models, represents barriers to profile molecularly targeted therapies for these tumors. Thus, genetically engineered mouse models have been identified to evaluate the interplay between Nf1-deficient tumor cells and nonneoplastic stromal cells to evaluate potential therapies for these neoplasms. Future treatments might also consider targeting the nonneoplastic cells in NF1-LGGs to reduce tumor growth and neurologic morbidity in affected children.

The therapeutic potential of targeting the PI3K pathway in pediatric brain tumors

Central nervous system tumors are the most common cancer type in children and the leading cause of cancer related deaths. There is therefore a need to develop novel treatments. Large scale profiling studies have begun to identify alterations that could be targeted therapeutically, including the phosphoinositide 3-kinase (PI3K) signaling pathway, which is one of the most commonly activated pathways in cancer with many inhibitors under clinical development. PI3K signaling has been shown to be aberrantly activated in many pediatric CNS neoplasms. Pre-clinical analysis supports a role for PI3K signaling in the control of tumor growth, survival and migration as well as enhancing the cytotoxic effects of current treatments. Based on this evidence agents targeting PI3K signaling have begun to be tested in clinical trials of pediatric cancer patients. Overall, targeting the PI3K pathway presents as a promising strategy for the treatment of pediatric CNS tumors. In this review we examine the genetic alterations found in the PI3K pathway in pediatric CNS tumors and the pathological role it plays, as well as summarizing the current pre-clinical and clinical data supporting the use of PI3K pathway inhibitors for the treatment of these tumors.

Surgical and molecular considerations in the treatment of pediatric thalamopeduncular tumors

OBJECTIVE Thalamopeduncular tumors are a group of pediatric low-grade gliomas that arise at the interface of the thalamus and brainstem peduncle. They typically occur within the first 2 decades of life, presenting with progressive spastic hemiparesis. Treatment strategies, including surgical intervention, have varied significantly. The authors present their experience in the treatment of 13 children, ages 2-15 years, with non-neurofibromatosis-related pilocytic astrocytomas located in the thalamopeduncular region. METHODS Between 2003 and 2016, 13 children presenting with progressive spastic hemiparesis due to a pilocytic astrocytoma at the interface of the thalamus and cerebral peduncles were identified. Medical records were reviewed retrospectively for clinical, radiological, pathological, and surgical data. Formalin-fixed, paraffin-embedded tissue was obtained for 12 cases and tested for KIAA1549-BRAF fusion and BRAF V600E point mutation. RESULTS On preoperative diffusion tensor imaging tractography (performed in 12 patients), the ipsilateral corticospinal tract was displaced laterally in 1 case (8.3%), medially in 1 case (8.3%), anterolaterally in 10 cases (83%), and posteriorly in no cases. Ten patients underwent resection via a transtemporal, transchoroidal approach, which was chosen to avoid further damage to motor function in cases of tumors that caused anterolateral or medial corticospinal tract displacement. With this approach, complications included hemianopia, oculomotor palsy, and tremor at a rate of 50%. Among the 12 patients with obtainable follow-up (mean 50.9 months), none received adjuvant therapy, and only 2 (17%) experienced recurrence or progression. KIAA1549-BRAF fusions were present in 10 cases (83%), while BRAF V600E was absent (0%). The 2 fusion-negative tumors had clinical features atypical for the series, including multi-focality and infiltration. CONCLUSIONS Transcortical, transchoroidal resection of thalamopeduncular tumors through the middle temporal gyrus allows for a high rate of gross-total resection and cure. Diffuse tensor tractography is a critical component of the preoperative planning process to determine the location of white matter tracts in proximity. Molecular status may correlate with clinical features, and the presence of BRAF lesions offers an additional target for future novel therapeutics.

Pediatric low-grade gliomas: implications of the biologic era

For the past decade, it has been recognized that pediatric low-grade gliomas (LGGs) and glial-neuronal tumors carry distinct molecular alterations with resultant aberrant intracellular signaling in the Ras-mitogen-activated protein kinase pathway. The conclusions and recommendations of a consensus conference of how best to integrate the growing body of molecular genetic information into tumor classifications and, more importantly, for future treatment of pediatric LGGs are summarized here. There is uniform agreement that molecular characterization must be incorporated into classification and is increasingly critical for appropriate management. Molecular-targeted therapies should be integrated expeditiously, but also carefully into the management of these tumors and success measured not only by radiographic responses or stability, but also by functional outcomes. These trials need to be carried out with the caveat that the long-term impact of molecularly targeted therapy on the developing nervous system, especially with long duration treatment, is essentially unknown.

Novel drugs in pediatric gliomas

Astrocytomas (gliomas) are the most common primary brain tumors among adults and second most frequent neoplasm among children. New ideas and novel approaches are being explored world over with aim to devise better management strategeies for this deadly pathological state. We searched the electronic database PubMed for pre-clinical as well as clinical controlled trials reporting importance of various therapeutic drugs against gliomas. It was observed clearly that this approach of using therapeutic drugs is clearly evolving and has been observed to be promising future therapeutic avenue against gliomas. The searched literature on whole revealed that although gliomas are treated aggressively with surgery, chemotherapy and radiation, treatment resistance, drug toxicity and poor response rates among pediatric glioma patients, continue to drive the need to discover new and more effective chemotherapeutic agents. The present review is focused on the latest updates in therapeutic drugs against gliomas in pediatric patients. The important chemo-therapeutics discussed in this review included alkylating agents like temoxolomide, derivatives of platinum, nitrosoureas, topoisomerases, angiogenesis inhibitors and cytomegalovirus as therapeutic agents.

Conventional chemotherapy and perspectives for molecular-based oncological treatment in pediatric hemispheric low-grade gliomas

INTRODUCTION

Pediatric low-grade gliomas (PLGG) are the most common primary central nervous system tumor in children. Patients in whom gross total resection can be achieved have an excellent overall (OS) and event-free survival (EFS) and do not require adjuvant therapy. However, children with unresectable tumors often experience multiple progressions and require additional treatment.

CONVENTIONAL CHEMOTHERAPY

Radiotherapy results in long-term tumor control, but it is associated with significant toxicity, making chemotherapy the preferred therapeutic option. Several chemotherapy combinations have been found to be successful in PLGG, but 5-year EFS has been below 60 % with most of them.

MOLECULAR-BASED TREATMENT

Recent molecular advances have led to a better understanding of the molecular pathways involved in the biology of LGG, allowing the development of promising tumor-specific, molecularly targeted therapies.

Exploiting Laboratory Insights to Improve Outcomes of Pediatric Central Nervous System Tumors

Over a relatively short period of time, owing to improvements in biotechnology, our ability to identify the molecular mechanisms within pediatric brain tumors has dramatically increased. These findings have reshaped the way that we describe these diseases and have provided insights into how to better treat these often devastating diseases. Although still far from reaching the full therapeutic potential these advancements hold, the impact of these findings is steadily taking hold of pediatric brain tumor management. In this article, we summarize the major discoveries within three common pediatric brain tumor categories; medulloblastoma, ependymoma, and low-grade glioma. We discuss the current impact of these findings on treatment and the direction these findings may take the field of pediatric neuro-oncology.

Exploiting molecular biology for diagnosis and targeted management of pediatric low-grade gliomas

The majority of brain tumors arising in children are low-grade gliomas. Although historically categorized together as pediatric low-grade gliomas (PLGGs), there is significant histologic and genetic diversity within this group. In general, prognosis for PLGGs is excellent, and limitation of sequelae from tumor and treatment is paramount. Advances in high-throughput genetic sequencing and gene expression profiling are fundamentally changing the way PLGGs are classified and managed. Here, we review the histologic subtypes and highlight how recent advances in elucidating the molecular pathogenesis of these tumors have refined diagnosis and prognostication. Additionally, we discuss how characterizing specific genetic alterations has paved the way for the rational use of targeted therapies that are currently in various phase clinical trials.

Erlotinib augmentation with dapsone for rash mitigation and increased anti-cancer effectiveness

BACKGROUND

The epidermal growth factor receptor tyrosine kinase inhibitor erlotinib has failed in many ways to be as potent in the anti-cancer role as pre-clinical studies would have suggested. This paper traces some aspects of this failure to a compensatory erlotinib-mediated increase in interleukin-8. Many other-but not all- cancer chemotherapeutic cytotoxic drugs also provoke a compensatory increase in a malignant clone's interleukin-8 synthesis. Untreated glioblastoma and other cancer cells themselves natively synthesize interleukin-8. Interleukin-8 has tumor growth promoting, mobility and metastasis formation enhancing, effects as well as pro-angiogenesis effects.

FINDINGS

The old sulfone antibiotic dapsone- one of the very first antibiotics in clinical use- has demonstrated several interleukin-8 system inhibiting actions. Review of these indicates dapsone has potential to augment erlotinib effectiveness. Erlotinib typically gives a rash that has recently been proven to come about via an erlotinib triggered up-regulated keratinocyte interleukin-8 synthesis. The erlotinib rash shares histological features reminiscent of typical neutrophilic dermatoses. Dapsone has an established therapeutic role in current treatment of other neutrophilic dermatoses.

CONCLUSION

Thus, dapsone has potential to both improve the quality of life in erlotinib treated patients by amelioration of rash as well as to short-circuit a growth-enhancing aspect of erlotinib when used in the anti-cancer role.

Pediatric Brain Tumors: Innovative Genomic Information Is Transforming the Diagnostic and Clinical Landscape

Pediatric neuro-oncology has undergone an exciting and dramatic transformation during the past 5 years. This article summarizes data from collaborative group and institutional trials that have advanced the science of pediatric brain tumors and survival of patients with these tumors. Advanced genomic analysis of the entire spectrum of pediatric brain tumors has heralded an era in which stakeholders in the pediatric neuro-oncology community are being challenged to reconsider their current research and diagnostic and treatment strategies. The incorporation of this new information into the next-generation treatment protocols will unleash new challenges. This review succinctly summarizes the key advances in our understanding of the common pediatric brain tumors (ie, medulloblastoma, low- and high-grade gliomas, diffuse intrinsic pontine glioma, and ependymoma) and some selected rare tumors (ie, atypical teratoid/rhabdoid tumor and CNS primitive neuroectodermal tumor). The potential impact of this new information on future clinical protocols also is discussed. Cutting-edge genomics technologies and the information gained from such studies are facilitating the identification of molecularly defined subgroups within patients with particular pediatric brain tumors. The number of evaluable patients in each subgroup is small, particularly in the subgroups of rare diseases. Therefore, international collaboration will be crucial to draw meaningful conclusions about novel approaches to treating pediatric brain tumors.

Review of low-grade gliomas in children--evolving molecular era and therapeutic insights

Low-grade gliomas are the commonest brain tumor in children comprising heterogeneous pathological entities. Though the overall prognosis is good, unresectable, and recurrent or progressive tumors in eloquent areas of the brain remain major therapeutic challenge even with advances in chemotherapeutic strategies. With the evolving surge of molecular data, improved understanding of the biology of these tumors is now perceivable that could provide insights into novel therapies. We hope the new era will enable us to profile comprehensive histopathological/molecular classification and prognostic molecular markers in these tumors and guide us to tailor optimal targeted therapy.

Therapeutic targets in pilocytic astrocytoma based on genetic analysis

Pilocytic astrocytoma (PA) is the most common astrocytic neoplasm of childhood. Patients have an extremely favorable prognosis after surgical resection, qualifying tumors for a grade I designation by the World Health Organization. The molecular data on PA support a key role for the BRAF oncogene in the pathogenesis of these tumors, with the KIAA1549-BRAF fusion being the most common alteration identified in sporadic cases, particularly those occurring in the posterior fossa. Constitutive activation of BRAF leads to downstream activation of the MEK/MAPK/ERK/p16 pathway, which interestingly is also used by cells to activate oncogene-induced senescence (OIS). In fact, the presence of an active OIS pathway might explain the periods of dormancy or spontaneous regression or both, that can be seen in PA. In addition to reviewing the historical evolution, clinicopathologic, predictive, prognostic, and molecular features of PA, we discuss current therapeutic strategies and the caveats that should be considered for the development of therapies that could be used to more effectively treat challenging cases. Individualized treatment requires identification of the type of MAPK alteration, as several alterations in BRAF have been described in addition to the KIAA1549-BRAF fusion. Combination regimens would also appear crucial to achieve tumor eradication and prevent the development of drug resistance. Balancing mitogen-activated protein kinases (MAPK) pathway inhibition with abrogation of an active OIS should be carefully considered as well to preserve any existing protective pathways. Importantly, PAs are largely indolent tumors, and care should be taken to avoid overtreatment, as aggressive therapy could cause more harm than good.

Improving outcomes for neurofibromatosis 1-associated brain tumors

Children and adults with neurofibromatosis type 1 (NF1) are predisposed to developing CNS tumors, including optic pathway gliomas (OPGs), brainstem gliomas (BSGs) and high-grade gliomas. Although current first-line treatments for low-grade gliomas (OPGs and BSGs) may prevent further tumor growth, they rarely result in restoration of the associated visual or neurological deficits. The availability of accurate small-animal models of NF1-associated brain tumors has established tractable experimental platforms for the discovery and evaluation of promising therapeutic agents. On the basis of these preclinical studies, biologically targeted agents are now being evaluated in children with NF1-associated low-grade brain tumors. Collectively, these models have also begun to reveal potential neuroprotective and risk assessment strategies for this brain tumor-prone population.

Neurofibromatosis-related tumors: emerging biology and therapies

PURPOSE OF REVIEW

Over the past decade, substantial insight into the biological function of the tumor suppressors neurofibromin (NF1) and Merlin (NF2) has been gained. The purpose of this review is to highlight some of the major advances in our understanding of the biology of neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2) as they relate to the development of novel therapies for these disorders.

RECENT FINDINGS

The development of increasingly sophisticated preclinical models over the recent years has provided the platform from which to rationally develop molecular targeted therapies for both NF1 and NF2-related tumors, such as within the Department of Defense-sponsored Neurofibromatosis Clinical Trials Consortium.

SUMMARY

Clinical trials with molecular-targeted therapies have become a reality for neurofibromatosis patients, and hold substantial promise for improving the morbidity and mortality of individuals affected with these disorders.

Advances in the management of low-grade gliomas

Low-grade gliomas (LGGs) represent the most common childhood brain tumors and are a histologically heterogenous group of tumors. Most LGGs are surgically resectable with excellent 10-year overall survival outcomes of more than 90 % with surgery alone. Tumors not amenable to surgical resection and those with an aggressive biology are more challenging to treat. Conventional radiotherapy is a more efficacious method of long-term tumor control than chemotherapy. However, radiation is associated with significant cognitive, endocrine, and cerebrovascular late effects, making chemotherapy an often-preferred modality over radiotherapy, especially in younger children. Multiple chemotherapy regimens have been evaluated over the past few decades with comparable survival outcomes and differing toxicity profiles. Newer regimens containing antiangiogenic agents also show promise. Recent molecular studies have implicated the BRAF oncogene, a key regulator of the MAPK pathway, and the AKT/mTOR pathway in pediatric LGG tumorigenesis. This has opened up promising new avenues for targeted therapy, with many agents currently under investigation.

Targeted therapy in pediatric low-grade glioma

Collectively, pediatric low-grade gliomas account for most brain tumors reported in children. Surgery is typically curable for operable lesions. However, more effective therapies are required for inaccessible tumors, both to overcome refractory disease and to minimize the toxicity associated with conventional adjuvant chemotherapy and radiotherapy regimens. Recent years have witnessed rapid improvements in our understanding of the molecular pathogenesis of several childhood tumors, including low-grade gliomas. As a result, several novel compounds targeting and inhibiting critical components of molecular signaling pathways purported to be overactive in the disease have been developed. This article summarizes the most recent literature evaluating such novel targeted agents in childhood low-grade gliomas.

Molecular profiling of childhood cancer: Biomarkers and novel therapies

BACKGROUND

Technological advances including high-throughput sequencing have identified numerous tumor-specific genetic changes in pediatric and adolescent cancers that can be exploited as targets for novel therapies.

SCOPE OF REVIEW

This review provides a detailed overview of recent advances in the application of target-specific therapies for childhood cancers, either as single agents or in combination with other therapies. The review summarizes preclinical evidence on which clinical trials are based, early phase clinical trial results, and the incorporation of predictive biomarkers into clinical practice, according to cancer type.

MAJOR CONCLUSIONS

There is growing evidence that molecularly targeted therapies can valuably add to the arsenal available for treating childhood cancers, particularly when used in combination with other therapies. Nonetheless the introduction of molecularly targeted agents into practice remains challenging, due to the use of unselected populations in some clinical trials, inadequate methods to evaluate efficacy, and the need for improved preclinical models to both evaluate dosing and safety of combination therapies.

GENERAL SIGNIFICANCE

The increasing recognition of the heterogeneity of molecular causes of cancer favors the continued development of molecularly targeted agents, and their transfer to pediatric and adolescent populations.

Advances in paediatric cancer treatment

Four out of five children diagnosed with cancer can be cured with contemporary cancer therapy. This represents a dramatic improvement since 50 years ago when the cure rate of childhood cancer was <25% in the pre-chemotherapy era. Over the past ten years, while improvement in overall survival (OS) has been marginal, progress in pediatric oncology lies with adopting risk-adapted therapeutic approach. This has been made possible through identifying clinical and biologic prognostic factors with rigorous research and stratifying patients using these risk factors, and subsequently modifying therapy according to risk group assignment. This review provides a perspective for eight distinct pediatric malignancies, in which significant advances in treatment were made in the last decade and are leading to changes in standard of care. This includes four hematologic malignancies [acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL)] and four solid tumors [medulloblastoma (MB), low grade glioma (LGG), neuroblastoma (NB) and Ewing sarcoma (ES)]. Together, they comprise 60% of childhood cancer. Improved patient outcome is not limited to better survival, but encompasses reducing both short and long-term treatment-related complications which is as important as cure, given the majority of childhood cancer patients will become long-term survivors. Risk-adapted approach allows treatment intensification in the high-risk cohort while therapy can be de-escalated in the low-risk to minimize toxicity and late sequelae without compromising survival. Advances in medical research technology have also led to a rapid increase in the understanding of the genetics of childhood cancer in the last decade, facilitating identification of molecular targets that can potentially be exploited for therapeutic benefits. As we move into the era of targeted therapeutics, searching for novel agents that target specific genetic lesions becomes a major research focus. We provide an overview of seven novel agents (bevacizumab, bortezomib, vorinostat, sorafenib, tipifarnib, erlotinib and mTOR inhibitors), which have been most frequently pursued in childhood cancers in the last decade, as well as reporting the progress of clinical trials involving these agents.

Integrated next-generation sequencing and avatar mouse models for personalized cancer treatment

BACKGROUND

Current technology permits an unbiased massive analysis of somatic genetic alterations from tumor DNA as well as the generation of individualized mouse xenografts (Avatar models). This work aimed to evaluate our experience integrating these two strategies to personalize the treatment of patients with cancer.

METHODS

We performed whole-exome sequencing analysis of 25 patients with advanced solid tumors to identify putatively actionable tumor-specific genomic alterations. Avatar models were used as an in vivo platform to test proposed treatment strategies.

RESULTS

Successful exome sequencing analyses have been obtained for 23 patients. Tumor-specific mutations and copy-number variations were identified. All samples profiled contained relevant genomic alterations. Tumor was implanted to create an Avatar model from 14 patients and 10 succeeded. Occasionally, actionable alterations such as mutations in NF1, PI3KA, and DDR2 failed to provide any benefit when a targeted drug was tested in the Avatar and, accordingly, treatment of the patients with these drugs was not effective. To date, 13 patients have received a personalized treatment and 6 achieved durable partial remissions. Prior testing of candidate treatments in Avatar models correlated with clinical response and helped to select empirical treatments in some patients with no actionable mutations.

CONCLUSION

The use of full genomic analysis for cancer care is encouraging but presents important challenges that will need to be solved for broad clinical application. Avatar models are a promising investigational platform for therapeutic decision making. While limitations still exist, this strategy should be further tested.

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.

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.

Overcoming the blood-brain barrier in chemotherapy treatment of pediatric brain tumors

Pediatric brain tumors are most common cancers in childhood and among the leading causes of death in children. Chemotherapy has been used as adjuvant (i.e. after) or neoadjuvant (i.e. before) therapy to surgery and radiotherapy for the management of pediatric brain tumors for more than four decades and gained more attention in the recent two decades. Although chemotherapy has demonstrated its effectiveness in the management of some pediatric brain tumors, failure or inactiveness of chemotherapy is commonly met in the clinics and clinical trials. Some of these failures might be attributed to the blood-brain barrier (BBB), limiting the penetration of systemically administered chemotherapeutics into pediatric brain tumors. Therefore, various strategies have been developed and used to address this issue. Herein, we review different methods reported in the literature to circumvent the BBB for enhancing the present of chemotherapeutics in the brain to treat pediatric brain tumors.

Radiotherapy in pediatric pilocytic astrocytomas. A subgroup analysis within the prospective multicenter study HIT-LGG 1996 by the German Society of Pediatric Oncology and Hematology (GPOH)

PURPOSE

We evaluated clinical outcomes in the subset of patients who underwent radiotherapy (RT) due to progressive pilocytic astrocytoma within the Multicenter Treatment Study for Children and Adolescents with a Low Grade Glioma HIT-LGG 1996.

PATIENTS AND METHODS

Eligibility criteria were fulfilled by 117 patients. Most tumors (65 %) were located in the supratentorial midline, followed by the posterior fossa (26.5 %) and the cerebral hemispheres (8.5 %). Median age at the start of RT was 9.2 years (range 0.7-17.4 years). In 75 cases, external fractionated radiotherapy (EFRT) was administered either as first-line nonsurgical treatment (n = 58) or after progression following primary chemotherapy (n = 17). The median normalized total dose was 54 Gy. Stereotactic brachytherapy (SBT) was used in 42 selected cases.

RESULTS

During a median follow-up period of 8.4 years, 4 patients (3.4 %) died and 33 (27.4 %) experienced disease progression. The 10-year overall (OS) and progression-free survival (PFS) rates were 97 and 70 %, respectively. No impact of the RT technique applied (EFRT versus SBT) on progression was observed. The 5-year PFS was 76 ± 5 % after EFRT and 65 ± 8 % after SBT. Disease progression after EFRT was not influenced by gender, neurofibromatosis type 1 (NF1) status, tumor location (hemispheres versus supratentorial midline versus posterior fossa), age or prior chemotherapy. Normalized total EFRT doses of more than 50.4 Gy did not improve PFS rates.

CONCLUSION

EFRT plays an integral role in the treatment of pediatric pilocytic astrocytoma and is characterized by excellent tumor control. A reduction of the normalized total dose from 54 to 50.4 Gy appears to be feasible without jeopardizing tumor control. SBT is an effective treatment alternative.

Gliomas in children

OPINION STATEMENT

Gliomas are the most common brain tumor in children and represent nearly 50 % of all pediatric central nervous system (CNS) tumors. They are a heterogeneous group of diseases, ranging from highly malignant and frequently fatal to histologically benign and curable by surgery alone. A uniform treatment approach to these tumors is not practical, due to their histological and biological heterogeneity. Low-grade gliomas (LGGs) are best treated with maximally safe surgical resection, generally achievable for hemispheric or cerebellar locations. Patients with deep midline, optic pathway/hypothalamic, and brain stem locations should undergo subtotal resection or biopsy only. If a complete resection is not feasible, subtotal resection followed by adjuvant chemotherapy or radiotherapy is the standard approach; however, observation alone with serial neuroimaging is used in some asymptomatic, surgically inaccessible lesions. Chemotherapy is used first-line in cases of residual or progressive disease, to avoid or delay radiation therapy and its associated side effects. Regimens demonstrating objective responses and increased progression free survival (PFS) include carboplatin and vincristine (CV), thioguanine/procarbazine/CCNU/vincristine (TPCV), or weekly vinblastine. High-grade gliomas (HGGs) are less common in children than in adults, though are similar in their aggressive clinical behavior, resistance to therapy, and dismal outcomes. There is not a single "standard of care" therapy for non-metastatic HGGs, but generally accepted is an aggressive attempt at a complete surgical resection, followed by multimodality therapy with focal radiation and chemotherapy. The use of temozolomide (TMZ) during and following radiotherapy is common, though it appeared not to improve the outcome in a cooperative group clinical trial when compared to an historical control cohort. The angiogenesis inhibitor bevacizumab, used alone or in combination with irinotecan, is also commonly used as maintenance therapy after radiation. Current trials are prospectively comparing TMZ to newer agents (vorinostat, bevacizumab) in a randomized phase II trial. Brainstem gliomas are a unique category of childhood gliomas. Approximately 80 % of childhood brainstem gliomas arise within the pons as diffuse intrinsic pontine gliomas (DIPG). When biopsied, these are usually HGGs and carry a dismal prognosis. Standard therapy is focal radiation (54-58 Gy), preferably on a clinical trial testing concurrent chemotherapy or biologic agent. No standard chemotherapy agent has impacted survival. The remaining 20 % of brainstem gliomas are low-grade, arise in the midbrain, dorsal medulla, or cervicomedullary junction, and are indolent in nature with a much better prognosis. Improvement in the outcome of all childhood gliomas will require increased knowledge of the underlying biology of these tumors, in order to treat with more biologically based and precise therapies.

Pilocytic astrocytoma: a disease with evolving molecular heterogeneity

Pilocytic astrocytoma, the most common pediatric brain tumor, is a clinically and molecularly heterogeneous disease that occurs most often in the cerebellum and hypothalamic and chiasmatic regions. Classically, pilocytic astrocytomas are driven by the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. Recently described genetic aberrations involving this pathway are critical for tumorigenesis. Tandem duplication of 7q34 encodes BRAF and produces several KIAA1549-BRAF novel oncogenic fusions. Activating point mutations of BRAF, such as BRAF (V600E), also lead to pilocytic astrocytoma. Loss of the NF1 gene allows hyperactivation of the oncogene KRAS. In this review, we discuss the current understanding of the novel molecular aberrations described in pilocytic astrocytomas and their clinical relevance for prognosis and treatment. The prognostic indications of these aberrations are discussed with regard to tumor location, tumor pathology, and patient age. A better understanding of the evolving molecular heterogeneity of pilocytic astrocytomas offers hope for developing molecularly targeted therapeutic armamentariums.

Optic pathway gliomas in neurofibromatosis-1: controversies and recommendations

Optic pathway glioma (OPG), seen in 15% to 20% of individuals with neurofibromatosis type 1 (NF1), account for significant morbidity in young children with NF1. Overwhelmingly a tumor of children younger than 7 years, OPG may present in individuals with NF1 at any age. Although many OPG may remain indolent and never cause signs or symptoms, others lead to vision loss, proptosis, or precocious puberty. Because the natural history and treatment of NF1-associated OPG is different from that of sporadic OPG in individuals without NF1, a task force composed of basic scientists and clinical researchers was assembled in 1997 to propose a set of guidelines for the diagnosis and management of NF1-associated OPG. This new review highlights advances in our understanding of the pathophysiology and clinical behavior of these tumors made over the last 10 years. Controversies in both the diagnosis and management of these tumors are examined. Finally, specific evidence-based recommendations are proposed for clinicians caring for children with NF1.