A critical assessment of using ChatGPT for extracting structured data from clinical notes

Existing natural language processing (NLP) methods to convert free-text clinical notes into structured data often require problem-specific annotations and model training. This study aims to evaluate ChatGPT's capacity to extract information from free-text medical notes efficiently and comprehensively. We developed a large language model (LLM)-based workflow, utilizing systems engineering methodology and spiral "prompt engineering" process, leveraging OpenAI's API for batch querying ChatGPT. We evaluated the effectiveness of this method using a dataset of more than 1000 lung cancer pathology reports and a dataset of 191 pediatric osteosarcoma pathology reports, comparing the ChatGPT-3.5 (gpt-3.5-turbo-16k) outputs with expert-curated structured data. ChatGPT-3.5 demonstrated the ability to extract pathological classifications with an overall accuracy of 89%, in lung cancer dataset, outperforming the performance of two traditional NLP methods. The performance is influenced by the design of the instructive prompt. Our case analysis shows that most misclassifications were due to the lack of highly specialized pathology terminology, and erroneous interpretation of TNM staging rules. Reproducibility shows the relatively stable performance of ChatGPT-3.5 over time. In pediatric osteosarcoma dataset, ChatGPT-3.5 accurately classified both grades and margin status with accuracy of 98.6% and 100% respectively. Our study shows the feasibility of using ChatGPT to process large volumes of clinical notes for structured information extraction without requiring extensive task-specific human annotation and model training. The results underscore the potential role of LLMs in transforming unstructured healthcare data into structured formats, thereby supporting research and aiding clinical decision-making.

Potential endpoints for assessment of bone health in persons with neurofibromatosis type 1

Neurofibromatosis type 1 is a genetic syndrome characterized by a wide variety of tumor and non-tumor manifestations. Bone-related issues, such as scoliosis, tibial dysplasia, and low bone mineral density, are a significant source of morbidity for this population with limited treatment options. Some of the challenges to developing such treatments include the lack of consensus regarding the optimal methods to assess bone health in neurofibromatosis type 1 and limited data regarding the natural history of these manifestations. In this review, the Functional Committee of the Response Evaluation in Neurofibromatosis and Schwannomatosis International Collaboration: (1) presents the available techniques for measuring overall bone health and metabolism in persons with neurofibromatosis type 1, (2) reviews data for use of each of these measures in the neurofibromatosis type 1 population, and (3) describes the strengths and limitations for each method as they might be used in clinical trials targeting neurofibromatosis type 1 bone manifestations. The Response Evaluation in Neurofibromatosis and Schwannomatosis International Collaboration supports the development of a prospective, longitudinal natural history study focusing on the bone-related manifestations and relevant biomarkers of neurofibromatosis type 1. In addition, we suggest that the neurofibromatosis type 1 research community consider adding the less burdensome measurements of bone health as exploratory endpoints in ongoing or planned clinical trials for other neurofibromatosis type 1 manifestations to expand knowledge in the field.

Genomic profiling of subcutaneous patient-derived xenografts reveals immune constraints on tumor evolution in childhood solid cancer

Subcutaneous patient-derived xenografts (PDXs) are an important tool for childhood cancer research. Here, we describe a resource of 68 early passage PDXs established from 65 pediatric solid tumor patients. Through genomic profiling of paired PDXs and patient tumors (PTs), we observe low mutational similarity in about 30% of the PT/PDX pairs. Clonal analysis in these pairs show an aggressive PT minor subclone seeds the major clone in the PDX. We show evidence that this subclone is more immunogenic and is likely suppressed by immune responses in the PT. These results suggest interplay between intratumoral heterogeneity and antitumor immunity may underlie the genetic disparity between PTs and PDXs. We further show that PDXs generally recapitulate PTs in copy number and transcriptomic profiles. Finally, we report a gene fusion LRPAP1-PDGFRA. In summary, we report a childhood cancer PDX resource and our study highlights the role of immune constraints on tumor evolution.

Comprehensive characterization of patient-derived xenograft models of pediatric leukemia

Patient-derived xenografts (PDX) remain valuable models for understanding the biology and for developing novel therapeutics. To expand current PDX models of childhood leukemia, we have developed new PDX models from Hispanic patients, a subgroup with a poorer overall outcome. Of 117 primary leukemia samples obtained, successful engraftment and serial passage in mice were achieved in 82 samples (70%). Hispanic patient samples engrafted at a rate (51/73, 70%) that was similar to non-Hispanic patient samples (31/45, 70%). With a new algorithm to remove mouse contamination in multi-omics datasets including methylation data, we found PDX models faithfully reflected somatic mutations, copy-number alterations, RNA expression, gene fusions, whole-genome methylation patterns, and immunophenotypes found in primary tumor (PT) samples in the first 50 reported here. This cohort of characterized PDX childhood leukemias represents a valuable resource in that germline DNA sequencing has allowed the unambiguous determination of somatic mutations in both PT and PDX.

Osteosarcoma Explorer: A Data Commons With Clinical, Genomic, Protein, and Tissue Imaging Data for Osteosarcoma Research

PURPOSE

Osteosarcoma research advancement requires enhanced data integration across different modalities and sources. Current osteosarcoma research, encompassing clinical, genomic, protein, and tissue imaging data, is hindered by the siloed landscape of data generation and storage.

MATERIALS AND METHODS

Clinical, molecular profiling, and tissue imaging data for 573 patients with pediatric osteosarcoma were collected from four public and institutional sources. A common data model incorporating standardized terminology was created to facilitate the transformation, integration, and load of source data into a relational database. On the basis of this database, a data commons accompanied by a user-friendly web portal was developed, enabling various data exploration and analytics functions.

RESULTS

The Osteosarcoma Explorer (OSE) was released to the public in 2021. Leveraging a comprehensive and harmonized data set on the backend, the OSE offers a wide range of functions, including Cohort Discovery, Patient Dashboard, Image Visualization, and Online Analysis. Since its initial release, the OSE has experienced an increasing utilization by the osteosarcoma research community and provided solid, continuous user support. To our knowledge, the OSE is the largest (N = 573) and most comprehensive research data commons for pediatric osteosarcoma, a rare disease. This project demonstrates an effective framework for data integration and data commons development that can be readily applied to other projects sharing similar goals.

CONCLUSION

The OSE offers an online exploration and analysis platform for integrated clinical, molecular profiling, and tissue imaging data of osteosarcoma. Its underlying data model, database, and web framework support continuous expansion onto new data modalities and sources.

COVID-19 in people with neurofibromatosis 1, neurofibromatosis 2, or schwannomatosis

PURPOSE

People with pre-existing conditions may be more susceptible to severe COVID-19 when infected by SARS-CoV-2. The relative risk and severity of SARS-CoV-2 infection in people with rare diseases such as neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), or schwannomatosis (SWN) is unknown.

METHODS

We investigated the proportions of people with NF1, NF2, or SWN in the National COVID Cohort Collaborative (N3C) electronic health record data set who had a positive test result for SARS-CoV-2 or COVID-19.

RESULTS

The cohort sizes in N3C were 2501 (NF1), 665 (NF2), and 762 (SWN). We compared these with N3C cohorts of patients with other rare diseases (98-9844 individuals) and the general non-NF population of 5.6 million. The site- and age-adjusted proportion of people with NF1, NF2, or SWN who had a positive test result for SARS-CoV-2 or COVID-19 (collectively termed positive cases) was not significantly higher than in individuals without NF or other selected rare diseases. There were no severe outcomes reported in the NF2 or SWN cohorts. The proportion of patients experiencing severe outcomes was no greater for people with NF1 than in cohorts with other rare diseases or the general population.

CONCLUSION

Having NF1, NF2, or SWN does not appear to increase the risk of being SARS-CoV-2 positive or of being a patient with COVID-19 or of developing severe complications from SARS-CoV-2.

Phase II study of everolimus for recurrent or progressive pediatric ependymoma

Background

Preclinical studies have suggested that mTOR pathway signaling may be a potential therapeutic target for childhood ependymoma.

Methods

A phase II clinical trial (ClinicalTrials.gov identifier: NCT02155920) of single-agent everolimus was performed to test the hypothesis that mTOR pathway inhibition would result in tumor responses for children with recurrent and/or progressive ependymomas.

Results

Eleven subjects [sex: 4 females (36.4%); median age: 8 years (range: 2-15 years); race: 9 white; prior therapies: median 6 (range: 3-9)] were enrolled on the study. Ten primary tumors were located in the posterior fossa and one primary tumor was located in the spinal cord. Eight of 9 tumors were PF-A subtype epenydmomas. All subjects were treated with oral everolimus 4.5 mg/m²/day (each cycle = 28 days) that was titrated to achieve serum trough levels of 5-15 ng/ml. Overall, everolimus was well tolerated; except for a single event of grade 3 pneumonia, all adverse events were grade 1-2. No objective tumor responses were observed. Participating subjects experienced tumor progression and discontinued therapy after a median of 2 cycles of therapy (1 cycle = 2; 2 cycles = 6; 3, 4, and 8 cycles = 1 each).

Conclusions

Everolimus does not appear to have activity for children with recurrent or progressive PF-A ependymoma.

MEK inhibitors for neurofibromatosis type 1 manifestations: Clinical evidence and consensus

The wide variety of clinical manifestations of the genetic syndrome neurofibromatosis type 1 (NF1) are driven by overactivation of the RAS pathway. Mitogen-activated protein kinase kinase inhibitors (MEKi) block downstream targets of RAS. The recent regulatory approvals of the MEKi selumetinib for inoperable symptomatic plexiform neurofibromas in children with NF1 have made it the first medical therapy approved for this indication in the United States, the European Union, and elsewhere. Several recently published and ongoing clinical trials have demonstrated that MEKi may have potential benefits for a variety of other NF1 manifestations, and there is broad interest in the field regarding the appropriate clinical use of these agents. In this review, we present the current evidence regarding the use of existing MEKi for a variety of NF1-related manifestations, including tumor (neurofibromas, malignant peripheral nerve sheath tumors, low-grade glioma, and juvenile myelomonocytic leukemia) and non-tumor (bone, pain, and neurocognitive) manifestations. We discuss the potential utility of MEKi in related genetic conditions characterized by overactivation of the RAS pathway (RASopathies). In addition, we review practical treatment considerations for the use of MEKi as well as provide consensus recommendations regarding their clinical use from a panel of experts.

Targeted Therapies for the Neurofibromatoses

Over the past several years, management of the tumors associated with the neurofibromatoses has been recognized to often require approaches that are distinct from their spontaneous counterparts. Focus has shifted to therapy aimed at minimizing symptoms given the risks of persistent, multiple tumors and new tumor growth. In this review, we will highlight the translation of preclinical data to therapeutic trials for patients with neurofibromatosis, particularly neurofibromatosis type 1 and neurofibromatosis type 2. Successful inhibition of MEK for patients with neurofibromatosis type 1 and progressive optic pathway gliomas or plexiform neurofibromas has been a significant advancement in patient care. Similar success for the malignant NF1 tumors, such as high-grade gliomas and malignant peripheral nerve sheath tumors, has not yet been achieved; nor has significant progress been made for patients with either neurofibromatosis type 2 or schwannomatosis, although efforts are ongoing.

Insights into the Pathogenesis of NF1-Associated Neoplasms

Neurofibromatosis type 1 (NF1) is one of the most common neurocutaneous genetic disorders, presenting with different cutaneous features such as café-au-lait macules, intertriginous skin freckling, and neurofibromas. Although most of the disease manifestations are benign, patients are at risk for a variety of malignancies, including malignant transformation of plexiform neurofibromas. Numerous studies have investigated the mechanisms by which these characteristic neurofibromas develop, with progress made toward unraveling the various players involved in their complex pathogenesis. In this review, we summarize the current understanding of the cells that give rise to NF1 neoplasms as well as the molecular mechanisms and cellular changes that confer tumorigenic potential. We also discuss the role of the tumor microenvironment and the key aspects of its various cell types that contribute to NF1-associated tumorigenesis. An increased understanding of these intrinsic and extrinsic components is critical for developing novel therapeutic approaches for affected patients.

SNO 2020 diversity survey: defining demographics, racial biases, career success metrics and a path forward for the field of neuro-oncology

BACKGROUND

Neuro-oncology has grown tremendously since 2010, marked by increasing society membership, specialized clinical expertise, and new journals. Yet, modest improvement in racial/ethnic diversity amongst clinical trial participants, researchers and clinicians led us to conduct a survey to identify opportunities to enhance diversity and inclusiveness amongst neuro-oncology professionals.

METHODS

In summer 2020, the Women and Diversity Committee of the Society for Neuro-Oncology (SNO) distributed an anonymous online survey to members and affiliates including European Association of Neuro-Oncology (EANO), Asian Society for Neuro-Oncology (ASNO), Society for Neuro-Oncology Latin America (SNOLA) and Society for Neuro-Oncology Sub-Saharan Africa (SNOSSA). The survey captured personal and professional characteristics, biases, effective mentorship qualities, career service metrics and suggested field/society changes. Results were analyzed by geography, profession, age, racial/ethnic and sexual identity. Standard descriptive statistics characterized the study population.

RESULTS

The 386 respondents were predominantly female (58%) with a median age range of 40-49 years (31%), White (65%), and SNO members (97%). Most worked in North America (77%) in a research profession (67%). A majority of White respondents reported never experiencing biases (64%), while the majority of non-White respondents reported unconscious biases/microaggressions, followed by a lack of/limited mentorship. Qualitative assessments showcased that personal/professional success metrics were linked to needed improvements in diversity and inclusion efforts within the neuro-oncology field.

CONCLUSIONS

The prevalence of racial/ethnic biases and poor mentorship rates amongst underrepresented groups in neuro-oncology is high and potentially linked to the limited diverse representation amongst members and affiliates. These findings warrant a swift implementation of equity and inclusion practices within the neuro-oncology field.

Recent progress in the treatment of cancer in children

Although significant improvements have been made in the outcomes of children with cancer, the pace of improvement has slowed in recent years as the limits of therapy intensification may have been reached for many pediatric cancers. Furthermore, with increasing numbers of pediatric cancer survivors, the long-term side effects of treatment have become increasingly apparent. Therefore, attention has shifted to the use of molecularly targeted agents and immunotherapies to improve the outcomes of children who are not cured by traditional cytotoxic chemotherapies and to decrease exposure to cytotoxic chemotherapy and reduce late effects. This review describes the recent progress in the treatment of children with cancer, focusing in particular on diseases in which targeted and immunotherapeutic agents have made an impact.

Risk Factors for Bullying Victimization in Children with Neurofibromatosis Type 1 (NF1)

Neurofibromatosis type 1 (NF1) is an autosomal disorder associated with numerous physical stigmata. Children with NF1 are at known risk for attention-deficit/hyperactivity disorder (ADHD), academic struggles, and significant social difficulties and adverse social outcomes, including bullying victimization. The primary aim of this study was to identify risk factors associated with bullying victimization in children with NF1 to better inform clinicians regarding targets for prevention and clinical intervention. Children and a parent completed questionnaires assessing the bully victim status, and parents completed a measure of ADHD symptoms. Analyses were completed separately for parent-reported victimization of the child and the child’s self-report of victimization. According to the parent report, results suggest ADHD symptoms are a significant risk factor for these children being a target of bullying. Findings for academic disability were not conclusive, nor were findings related to having a parent with NF1. Findings indicate the need for further research into possible risk factors for social victimization in children with NF1. Results provide preliminary evidence that may guide clinicians working with children with NF1 and their parents in identifying higher-risk profiles that may warrant earlier and more intensive intervention to mitigate later risk for bullying victimization.

Clinical Outcomes and Patient-Matched Molecular Composition of Relapsed Medulloblastoma

We sought to investigate clinical outcomes of relapsed medulloblastoma and to compare molecular features between patient-matched diagnostic and relapsed tumors.

The Use of MEK Inhibitors in Neurofibromatosis Type 1-Associated Tumors and Management of Toxicities

Early-phase clinical trials using oral inhibitors of MEK, the mitogen-activated protein kinase kinase, have demonstrated benefit for patients with neurofibromatosis type 1 (NF1)-associated tumors, particularly progressive low-grade gliomas and plexiform neurofibromas. Given this potential of MEK inhibition as an effective medical therapy, the use of targeted agents in the NF1 population is likely to increase substantially. For clinicians with limited experience prescribing MEK inhibitors, concern about managing these treatments may be a barrier to use. In this manuscript, the Clinical Care Advisory Board of the Children's Tumor Foundation reviews the published experience with MEK inhibitors in NF1 and outlines recommendations for side-effect management, as well as monitoring guidelines. These recommendations can serve as a beginning framework for NF providers seeking to provide the most effective treatments for their patients. IMPLICATIONS FOR PRACTICE: Neurofibromatosis type 1 (NF1) clinical care is on the cusp of a transformative shift. With the success of recent clinical trials using MEK inhibitors, an increasing number of NF1 patients are being treated with MEK inhibitors for both plexiform neurofibromas and low-grade gliomas. The use of MEK inhibitors is likely to increase substantially in NF1. Given these changes, the Clinical Care Advisory Board of the Children's Tumor Foundation has identified a need within the NF1 clinical community for guidance for the safe and effective use of MEK inhibitors for NF1-related tumors. This article provides a review of the published experience of MEK inhibitors in NF1 and provides recommendations for monitoring and management of side effects.

Rate and frequency of bullying victimization in school-age children with neurofibromatosis type 1 (NF1)

Children and adolescents with the genetic, tumor predisposition syndrome neurofibromatosis type I (NF1) have varying degrees of physical stigmata characteristic of the disease and experience high rates of social difficulties. The present study was the first to formally examine the rate (i.e., percentage of participants) and frequency of bullying victimization in a school-age sample of individuals with NF1. Bullying is defined as harmful behavior that is intentional, repeated, and involves a power imbalance between perpetrators and targets. Given that physical stigmata are characteristic of NF1 to varying degrees, it was hypothesized that bullying experiences would be common in school-age children with NF1. The present study also examined factors including age, gender, and health care provider ratings of severity of physical stigmata on self-reported rates of bullying victimization. Eighty-one school-age children with NF1 and a parent completed established bullying questionnaires. Results showed about 62% of the sample reported being bullied at least once in the last year, with 24.7% reporting being bullied daily. Boys reported significantly greater frequencies of bullying than did girls. Unique differences of gender and level of physical stigmata emerged, such that girls with low stigmata burden experienced significantly higher rates of bullying than girls with high stigmata burden. No differences in frequencies of bullying between low stigmata boys and high stigmata boys were found. The present study suggests that rates of bullying in NF1 are very high, which may be undervalued among adults and medical professionals, given the lack of research on bullying toward youth with NF1. School psychologists are uniquely positioned to implement programs and interventions to address the high rate of bullying toward the school-age NF1 population. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Targeted MAPK Pathway Inhibitors in Patients With Disseminated Pilocytic Astrocytomas

This report presents a series of 5 pediatric patients with disseminated pilocytic astrocytomas and frequent nonfusion activating mutations. Genetic variants in these patients' tumors include BRAF p.Val600Glu, BRAF p.Val600Asp, and KRAS p.Gly60_Gln62ins7. The 2 patients with BRAF-mutated tumors were treated with dabrafenib or a combination of dabrafenib plus trametinib. The patients had either near complete resolution of the primary tumor (BRAF p.Val600Glu) or a stable primary tumor (BRAF p.Val600Asp). Both patients showed improvement in leptomeningeal dissemination without significant toxicity. Genomic testing of disseminated pilocytic astrocytomas, particularly those arising at extracerebellar locations, may result in the identification of mutations associated with ERK/MAPK activation. Patients with these activating mutations may benefit from targeted therapies.

Postoperative surveillance of pediatric cerebellar pilocytic astrocytoma

The purpose of this study was to identify the optimal frequency and duration of magnetic resonance imaging follow-up in children who had gross totally resected cerebellar pilocytic astrocytomas (CPAs). Our hypothesis was that following two MR examinations, separated by at least 3 months, showing no evidence of tumor, gross totally resected CPAs did not recur and no further imaging follow-up was necessary. Retrospective review of Neuro-Oncology database from 1/2000 to 7/2013 yielded 53 patients with CPAs that had preoperative imaging and >2 years post-operative imaging follow-up available. Pilocytic astrocytomas with brainstem involvement and patients with neurofibromatosis type I were excluded. Preoperative tumor volumes were calculated. The dates and reports of the examinations were tabulated. The median number of follow-up examinations was 9 over a median follow-up time of 6.05 years (2.07-12.28 years). Two consecutive MR examinations over at least a 3 month span demonstrated the smallest negative likelihood ratio of future recurrence (0.15). There was no association of recurrence with preoperative tumor volume. Among the 35 patients with gross total resection of their tumor and greater than two negative follow-up examinations, one recurrence (2.9 %) was identified, occurring 6.4 years after initial resection. Gross totally resected pediatric CPAs can recur, but this is exceedingly rare. Frequent surveillance (every 3-6 months) is suggested in patients with CPAs until absence of tumor is concluded on imaging and documented on two consecutive studies spaced at least 3 months apart. The likelihood of recurrence thereafter is low.

Pleomorphic xanthoastrocytoma of childhood: MR imaging and diffusion MR imaging features

BACKGROUND AND PURPOSE

Pleomorphic xanthoastrocytomas are rare astrocytic neoplasms of childhood and young adulthood. The purpose of this retrospective review was to evaluate MR imaging features of pediatric pleomorphic xanthoastrocytomas with an emphasis on diffusion MR imaging.

MATERIALS AND METHODS

Review of the neuro-oncology data base revealed 11 pediatric patients (range, 4.7-16.1 years) with pleomorphic xanthoastroacytomas with 9 of these patients having preoperative MR imaging available. Six patients had preoperative diffusion MR imaging. Demographics, histopathology slides, conventional imaging characteristics (location, cystic component, hemorrhage, enhancement, vasogenic edema, inner table scalloping), and ADC metrics (mean tumor ADC and tumor to normal brain ADC ratio) were evaluated.

RESULTS

Three pleomorphic xanthoastrocytomas had anaplastic features. Ten tumors were supratentorial. Two-thirds (6 of 9) of all tumors were either predominantly cystic or had cystic components, and three-fourths (6 of 8) of the supratentorial tumors had associated inner table scalloping. Seven of the 9 tumors had marked vasogenic edema (>10 mm). Mean tumoral ADC (n = 7) was 912 ± 219 × 10(-6) mm(2)/s (min-max: 617-1189). The tumor to normal brain ADC ratio was 1.14 ± 0.26 (min-max: 0.75-1.47).

CONCLUSIONS

Pleomorphic xanthoastrocytoma should be entertained in the differential diagnosis of peripheral supratentorial tumors that appear during childhood. Cysts, inner table scalloping, and marked vasogenic edema are relatively frequent features. Relatively low ADC values and ADC ratios are not uncommon in pleomorphic xanthoastrocytoma.

Wilms tumor in a child with L-2-hydroxyglutaric aciduria

We report a male infant with L-2-hydroxyglutaric aciduria and Wilms tumor. L-2-hydroxyglutaric aciduria is a rare, autosomal-recessive, inborn error of metabolism characterized by a variable degree of progressive encephalopathy. Of the fewer than 100 cases reported in the literature, at least 9 patients have developed tumors of the central nervous system. To our knowledge, the present case is the 1st example of an extracranial tumor associated with L-2-hydroxyglutaric aciduria. This observation potentially widens the tumor spectrum in this metabolic disorder and may lead to further insight into the relationship between L-2-hydroxyglutaric acid and cellular transformation.

Childhood medulloblastoma: current status of biology and treatment

Medulloblastoma, a primitive neuro-ectodermal tumour that arises in the posterior fossa, is the most common malignant brain tumour occurring in childhood. Over the past half century, the long-term survival for children with medulloblastoma has improved remarkably from a certain fatal diagnosis to a cancer that is often curable. Although overall survival for children with non-disseminated and non-anaplastic medulloblastoma can approach 80%, the current multidisciplinary therapeutic approach is not without long-term sequelae. Chemotherapy has improved the long-term survival and allowed for reductions in the amount of radiation given, thereby reducing some of the long-term toxicities. In this review, we describe the current understanding of the basic biology of medulloblastoma and report on the current active chemotherapeutic agents utilized in medulloblastoma therapy. Ultimately, our understanding of the basic biology of medulloblastoma may lead to further advances in therapy by providing targets that are more specific and potentially less toxic.

Activation of Ras is necessary and sufficient for upregulation of vanilloid receptor type 1 in sensory neurons by neurotrophic factors

We have analyzed signaling pathways involved in neurotrophic factor (NTF)-induced upregulation of nociceptive properties, specifically vanilloid receptor type 1 (VR1), by adult rat dorsal root ganglion neurons. Upregulation of VR1 by nerve growth factor and glial cell line-derived neurotrophic factor is partially blocked by a MEK inhibitor. Dominant negative Ras, but not Rap, blocks NTF-induced ERK activation and VR1 upregulation. Activated Ras mimics NTF-mediated induction of VR1 in dorsal root ganglion neurons. An inhibitor of phosphatidylinositol 3-kinase, LY294002, also inhibited NTF-induced VR1 upregulation. However, this may at least in part be due to a block of NTF-induced ERK activation. Constitutive simultaneous stimulation of both ERK and phosphatidylinositol 3-kinase is not sufficient for VR1 upregulation. Together, the data suggest that VR1 expression by dorsal root ganglion neurons is regulated by common Ras-dependent pathways.

BDNF activated TrkB/IRR receptor chimera promotes survival of sympathetic neurons through Ras and PI-3 kinase signaling

Insulin receptor-related receptor (IRR) expression is tightly coupled to the nerve growth factor (NGF) receptor, TrkA, throughout development. Expression of both receptors is primarily localized to neural crest derived sensory and sympathetic neurons. In contrast to TrkA, however, the physiological ligand for IRR is unknown. To analyze the intracellular signaling and potential function of the orphan IRR in neurons, an adenovirus expressing a TrkB/IRR chimeric receptor was used to infect cultured mouse superior cervical ganglion neurons that normally require NGF for survival. Brain derived neurotrophic factor (BDNF)-activated TrkB/IRR induced neuronal survival. We utilized numerous receptor mutants in order to identify the intracellular domains of IRR necessary for signaling and neuron survival. Finally, we employed adenovirus encoding dominant negative forms of the extracellular signal-regulated kinase (ERK) signaling cascade to demonstrate that IRR, like TrkA, requires ras activation to promote neuron survival. Therefore, by use of the chimeric TrkB/IRR receptor, we have demonstrated the ability of IRR to elicit activation of signaling cascades resulting in a biological response in superior cervical ganglion (SCG) neurons.

Loss of brain-derived neurotrophic factor-dependent neural crest-derived sensory neurons in neurotrophin-4 mutant mice

Peripheral ganglion neurons confer sensory information including touch, pain, temperature, and proprioception. Sensory modality is linked to specific neurotrophin (NTF) requirements. NT-3 supports survival of neurons that differentiate primarily into proprioceptors whereas nerve growth factor and brain-derived neurotrophic factor (BDNF) support subpopulations that transmit nociception and mechanoreception, respectively. We examined sensory neurons of gene-targeted mouse mutants at the NT-4, BDNF, NT-3, and TrkA loci. We show that NT-4 functions early in gangliogenesis, upstream of BDNF. In the absence of NT-4 function, BDNF-dependent, TrkB-expressing neurons fail to appear. The results are consistent with the model that precursor cells intended to become BDNF-dependent mechanoreceptors instead differentiate into NT-3-dependent proprioceptive neurons.

Requirement for nitric oxide activation of p21(ras)/extracellular regulated kinase in neuronal ischemic preconditioning

The mechanisms underlying neuronal ischemic preconditioning, a phenomenon in which brief episodes of ischemia protect against the lethal effects of subsequent periods of prolonged ischemia, are poorly understood. Ischemia can be modeled in vitro by oxygen-glucose deprivation (OGD). We report here that OGD preconditioning induces p21(ras) (Ras) activation in an N-methyl-D-aspartate receptor- and NO-dependent, but cGMP-independent, manner. We demonstrate that Ras activity is necessary and sufficient for OGD tolerance in neurons. Pharmacological inhibition of Ras, as well as a dominant negative mutant Ras, block OGD preconditioning whereas a constitutively active form of Ras promotes neuroprotection against lethal OGD insults. In contrast, the activity of phosphatidyl inositol 3-kinase is not required for OGD preconditioning because inhibition of phosphatidyl inositol 3-kinase with a chemical inhibitor or with a dominant negative mutant does not have any effect on the development of OGD tolerance. Furthermore, using recombinant adenoviruses and pharmacological inhibitors, we show that downstream of Ras the extracellular regulated kinase cascade is required for OGD preconditioning. Our observations indicate that activation of the Ras/extracellular regulated kinase cascade by NO is a critical mechanism for the development of OGD tolerance in cortical neurons, which may also play an important role in ischemic preconditioning in vivo.

Mouse tumor model for neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder characterized by increased incidence of benign and malignant tumors of neural crest origin. Mutations that activate the protooncogene ras, such as loss of Nf1, cooperate with inactivating mutations at the p53 tumor suppressor gene during malignant transformation. One hundred percent of mice harboring null Nf1 and p53 alleles in cis synergize to develop soft tissue sarcomas between 3 and 7 months of age. These sarcomas exhibit loss of heterozygosity at both gene loci and express phenotypic traits characteristic of neural crest derivatives and human NF1 malignancies.

A TrkB/insulin receptor-related receptor chimeric receptor induces PC12 cell differentiation and exhibits prolonged activation of mitogen-activated protein kinase

Insulin receptor-related receptor (IRR), an orphan receptor in the insulin receptor (IR) family of receptor tyrosine kinases, is primarily localized to neural crest-derived sensory neurons during embryonic development. Expression of IRR closely resembles that of the nerve growth factor receptor, TrkA. To analyze the signaling properties and function of IRR in PC12 cells, a TrkB/IRR hybrid receptor was used. In contrast to IR activation, brain-derived neurotrophic growth factor-mediated activation of the TrkB/IRR receptor resulted in differentiation rather than proliferation. Analysis of cytoplasmic substrates activated by the TrkB/IRR receptor indicates a signaling pathway similar to that of the IR. Mutagenesis studies further show that only TrkB/IRR receptors able to phosphorylate mitogen-activated protein kinase elicit a differentiation response. Our analysis indicates that prolonged kinetics of mitogen-activated protein kinase activation mediated by the TrkB/IRR chimeric receptor correlates with induction to differentiate.

Trks: signal transduction and intracellular pathways

The neurotrophin family of growth factors supports survival and differentiation of neurons in the developing vertebrate nervous system by binding activating receptor tyrosine kinases, the Trks. Activation of Trk receptors leads to stimulation of a number of intracellular signaling cascades including, among others, the ras/extracellular regulated kinase (erk) and the phosphatidylinositol-3 kinase (PI 3 kinase) cascades. Over the past several years, work in several neurotrophin responsive systems has begun to identify the role each of these signaling cascades plays in the cellular response to neurotrophins. It now appears that neurotrophins, in particular nerve growth factor (NGF), mediate their multiple effects through a number of distinct intracellular signaling cascades. In this review, we will overview the evidence implicating specific signaling cascades in aspects of the cellular response to the neurotrophins, specifically in response to activation of TrkA by NGF.

Nerve growth factor induces survival and differentiation through two distinct signaling cascades in PC12 cells

Nerve growth factor induces differentiation and survival of rat PC12 pheochromocytoma cells. The activation of the erk cascade has been implicated in transducing the multitude of signals induced by NGF. In order to explore the role of this signaling cascade in NGF mediated survival, differentiation and proliferation, we generated recombinant adenoviruses which express the intermediates of the erk cascade in their wild type, dominant negative and constitutively activated forms. We show that differentiation of PC12 cells requires activity of the ras/erk pathway, whereas inhibition of this pathway had no effect on survival or proliferation. Constitutively active forms of ras, raf and mek induced PC12 cell differentiation, while dominant interfering forms inhibited differentiation. Survival of PC12 cells in serum-free medium did not require activity of the ras/erk pathway. Instead, PI3 Kinase signaling was necessary for PC12 cell survival. Interestingly, constitutively activated versions of raf and mek were able to promote survival, but again this was dependent on activation of PI3 Kinase. Therefore, at least two distinct signaling pathways are required in PC12 cells for mediation of NGF functions.

p21 ras and phosphatidylinositol-3 kinase are required for survival of wild-type and NF1 mutant sensory neurons

Nerve growth factor (NGF) is a required differentiation and survival factor for sympathetic and a majority of neural crest-derived sensory neurons in the developing vertebrate peripheral nervous system. Although much is known about the function of NGF, the intracellular signaling cascade that it uses continues to be a subject of intense study. p21 ras signaling is considered necessary for sensory neuron survival. How additional intermediates downstream or in parallel may function has not been fully understood yet. Two intracellular signaling cascades, extra cellular regulated kinase (erk) and phosphatidylinositol-3 (PI 3) kinase, transduce NGF signaling in the pheochromocytoma cell line PC12. To elucidate the role these cascades play in survival and differentiation, we used a combination of recombinant adenoviruses and chemical inhibitors to perturb these pathways in sensory neurons from wild-type mice and mice deficient for neurofibromin in which the survival and differentiation pathway is constitutively active. We demonstrate that ras activity is both necessary and sufficient for the survival of embryonic sensory neurons. Downstream of ras, however, the erk cascade is neither required nor sufficient for neuron survival or overall differentiation. Instead, the activity of PI 3 kinase is necessary for the survival of the wild-type and neurofibromin-deficient neurons. Therefore, we conclude that in sensory neurons, NGF acts via a signaling pathway, which includes both ras and PI 3 kinase.