Browsing by Subject "neurofibromatosis type 1"

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    Comparison of multi-shot and single shot echo-planar diffusion tensor techniques for the optic pathway in patients with neurofibromatosis type 1
    (Springer, 2019-04) Ho, Chang Y.; Deardorff, Rachael; Kralik, Stephen F.; West, John D.; Wu, Yu-Chien; Shih, Chie-Schin; Radiology and Imaging Sciences, School of Medicine
    Purpose Diffusion tensor imaging (DTI) may be helpful in assessing optic pathway integrity as a marker for treatment in neurofibromatosis type 1 (NF1) patients with optic gliomas (OG). However, susceptibility artifacts are common in typical single-shot echo planar imaging (ssDTI). A readout-segmented multi-shot EPI technique (rsDTI) was utilized to minimize susceptibility distortions of the skull base and improve quantitative metrics. Methods Healthy controls, children with NF1 without OG, and NF1 with OG ± visual symptoms were included. All subjects were scanned with both rsDTI and ssDTI sequences sequentially. Diffusion metrics and deterministic fiber tracking were calculated. Tract count, volume, and length were also compared by a two-factor mixed ANOVA. Results Five healthy controls, 7 NF1 children without OG, and 12 NF1 children with OG were imaged. Six OG patients had visual symptoms. Four subjects had no detectable optic pathway fibers on ssDTI due to susceptibility, for which rsDTI was able to delineate. Tract count (p < 0.001), tract volume (p < 0.001), and FA (P < 0.001) were significantly higher for rsDTI versus ssDTI for all subjects. MD (p < 0.001) and RD (p < 0.001) were significantly lower for rsDTI vs ssDTI. Finally, MD, AD, and RD had a significantly lower difference in NF1 children with visual symptoms compared to NF1 children without visual symptoms only on ssDTI scans. Conclusion DTI with readout-segmented multi-shot EPI technique can better visualize the optic pathway and allow more confident measurements of anisotropy in NF1 patients. This is shown by a significant increase in FA, tract count, and volume with rsDTI versus ssDTI.
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    Ketotifen Modulates Mast Cell Chemotaxis to Kit-Ligand, but Does Not Impact Mast Cell Numbers, Degranulation, or Tumor Behavior in Neurofibromas of Nf1-Deficient Mice
    (American Association for Cancer Research, 2019-12-01) Burks, Ciersten A.; Rhodes, Steven D.; Bessler, Waylan K.; Chen, Shi; Smith, Abbi; Gehlhausen, Jeffrey R.; Hawley, Eric T.; Jiang, Li; Li, Xiaohong; Yuan, Jin; Lu, Qingbo; Jacobsen, Max; Sandusky, George E.; Jones, David R.; Clapp, D. Wade; Blakeley, Jaishri O.; Pediatrics, School of Medicine
    Neurofibromatosis Type 1 (NF1) is one of the most common genetic tumor predisposition syndromes in humans. Mutant NF1 results in dysregulated RAS allowing neoplasms throughout the neuroaxis. Plexiform neurofibromas (pNFs) afflict up to 50% of patients with NF1. They are complex tumors of the peripheral nerve that cause major morbidity via nerve dysregulation and mortality via conversion to malignant sarcoma. Genetically engineered mouse models (GEMMs) of NF1 provide valuable insights for the identification of therapies that have utility in people with pNF. Preclinical studies in GEMMs implicate mast cells and the c-Kit/Kit ligand pathway in pNF tumorigenesis. Kit ligand is a potent chemokine secreted by tumorigenic, Nf1-deficient Schwann cells. Ketotifen is an FDA-approved drug for the treatment of allergic conjunctivitis and asthma that promotes mast cell stabilization and has been used in prior case studies to treat or prevent pNFs. This study investigated the effect of ketotifen on mast cell infiltration and degranulation in the presence and absence of Kit ligand provocation and the effect of ketotifen on shrinking or preventing pNF formation in the Nf1flox/flox;PostnCre+ GEMM. Ketotifen decreased mast cell infiltration in response to exogenous Kit ligand administration, but did not affect mast cell degranulation. Importantly, ketotifen did not reduce mast cells numbers or activity in pNF and did not prevent pNF formation or decrease the volume of established pNF despite administration of pharmacologically active doses. These findings suggest ketotifen has limited use as monotherapy to prevent or reduce pNF burden in the setting of Nf1 mutations.
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    The path forward: 2015 International Children's Tumor Foundation conference on neurofibromatosis type 1, type 2, and schwannomatosis
    (Wiley, 2017-06) Blakely, Jaishri O.; Bakker, Annette; Barker, Anne; Clapp, Wade; Ferner, Rosalie; Fisher, Michael J.; Giovannini, Marco; Gutmann, David H.; Karajannis, Matthias A.; Kissil, Joseph L.; Legius, Eric; Lloyd, Alison C.; Packer, Roger J.; Ramesh, Vijaya; Riccardi, Vincent M.; Stevenson, David A.; Ullrich, Nicole J.; Upadhyaya, Meena; Stemmer-Rachamimov, Anat; Pediatrics, School of Medicine
    The Annual Children's Tumor Foundation International Neurofibromatosis Meeting is the premier venue for connecting discovery, translational and clinical scientists who are focused on neurofibromatosis types 1 and 2 (NF1 and NF2) and schwannomatosis (SWN). The meeting also features rare tumors such as glioma, meningioma, sarcoma, and neuroblastoma that occur both within these syndromes and spontaneously; associated with somatic mutations in NF1, NF2, and SWN. The meeting addresses both state of the field for current clinical care as well as emerging preclinical models fueling discovery of new therapeutic targets and discovery science initiatives investigating mechanisms of tumorigenesis. Importantly, this conference is a forum for presenting work in progress and bringing together all stakeholders in the scientific community. A highlight of the conference was the involvement of scientists from the pharmaceutical industry who presented growing efforts for rare disease therapeutic development in general and specifically, in pediatric patients with rare tumor syndromes. Another highlight was the focus on new investigators who presented new data about biomarker discovery, tumor pathogenesis, and diagnostic tools for NF1, NF2, and SWN. This report summarizes the themes of the meeting and a synthesis of the scientific discoveries presented at the conference in order to make the larger research community aware of progress in the neurofibromatoses.
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    SARC006: Phase II Trial of Chemotherapy in Sporadic and Neurofibromatosis Type 1 Associated Chemotherapy-Naive Malignant Peripheral Nerve Sheath Tumors
    (Hindawi, 2017) Higham, Christine S.; Steinberg, Seth M.; Dombi, Eva; Perry, Arie; Helman, Lee J.; Schuetze, Scott M.; Ludwig, Joseph A.; Staddon, Arthur; Milhem, Mohammed M.; Rushing, Daniel; Jones, Robin L.; Livingston, Michael; Goldman, Stewart; Moertel, Christopher; Wagner, Lars; Janhofer, David; Annunziata, Christina M.; Reinke, Denise; Long, Lauren; Viskochil, David; Baker, Larry; Widemann, Brigitte C.; Department of Medicine, School of Medicine
    Background. Worse chemotherapy response for neurofibromatosis type 1- (NF1-) associated compared to sporadic malignant peripheral nerve sheath tumors (MPNST) has been reported. Methods. We evaluated the objective response (OR) rate of patients with AJCC Stage III/IV chemotherapy-naive NF1 MPNST versus sporadic MPNST after 4 cycles of neoadjuvant chemotherapy, 2 cycles of ifosfamide/doxorubicin, and 2 cycles of ifosfamide/etoposide. A Simon optimal two-stage design was used (target response rate 40%). Results. 34 NF1 (median age 33 years) and 14 sporadic (median age 40 years) MPNST patients enrolled. Five of 28 (17.9%) evaluable NF1 MPNST patients had a partial response (PR), as did 4 of 9 (44.4%) patients with sporadic MPNST. Stable disease (SD) was achieved in 22 NF1 and 4 sporadic MPNST patients. In both strata, results in the initial stages met criteria for expansion of enrollment. Only 1 additional PR was observed in the expanded NF1 stratum. Enrollment was slower than expected and the trial closed before full accrual. Conclusions. This trial was not powered to detect differences in response rates between NF1 and sporadic MPNST. While the OR rate was lower in NF1 compared to sporadic MPNST, qualitative responses were similar, and disease stabilization was achieved in most patients.
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    Sleep and pulmonary outcomes for clinical trials of airway plexiform neurofibromas in NF1
    (AAN, 2016-08) Plotkin, Scott R.; Davis, Stephanie D.; Robertson, Kent A.; Akshintala, Srivandana; Allen, Julian; Fisher, Michael J.; Blakely, Jaishri O.; Widemann, Brigitte C.; Ferner, Rosalie E.; Marcus, Carole L.; Department of Pediatrics, School of Medicine
    Objective: Plexiform neurofibromas (PNs) are complex, benign nerve sheath tumors that occur in approximately 25%–50% of individuals with neurofibromatosis type 1 (NF1). PNs that cause airway compromise or pulmonary dysfunction are uncommon but clinically important. Because improvement in sleep quality or airway function represents direct clinical benefit, measures of sleep and pulmonary function may be more meaningful than tumor size as endpoints in therapeutic clinical trials targeting airway PN. Methods: The Response Evaluation in Neurofibromatosis and Schwannomatosis functional outcomes group reviewed currently available endpoints for sleep and pulmonary outcomes and developed consensus recommendations for response evaluation in NF clinical trials. Results: For patients with airway PNs, polysomnography, impulse oscillometry, and spirometry should be performed to identify abnormal function that will be targeted by the agent under clinical investigation. The functional group endorsed the use of the apnea hypopnea index (AHI) as the primary sleep endpoint, and pulmonary resistance at 10 Hz (R10) or forced expiratory volume in 1 or 0.75 seconds (FEV1 or FEV0.75) as primary pulmonary endpoints. The group defined minimum changes in AHI, R10, and FEV1 or FEV0.75 for response criteria. Secondary sleep outcomes include desaturation and hypercapnia during sleep and arousal index. Secondary pulmonary outcomes include pulmonary resistance and reactance measurements at 5, 10, and 20 Hz; forced vital capacity; peak expiratory flow; and forced expiratory flows. Conclusions: These recommended sleep and pulmonary evaluations are intended to provide researchers with a standardized set of clinically meaningful endpoints for response evaluation in trials of NF1-related airway PNs.
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    A Synthetic Lethal shRNA Screen and Genetic Proof of Concept Identifies RAC1 as a Novel Target to Disrupt Plexiform Neurofibroma Formation
    (2019-12) Mund, Julie Ann; Clapp, D. Wade; Goebl, Mark; Harrington, Maureen; Brutkiewicz, Randy
    Neurofibromatosis Type 1 (NF1) is a highly penetrant autosomal dominant genetic disorder where mutations in the tumor suppressor gene NF1 leads to decreased neurofibromin. The most debilitating manifestation is the presence of complex multilineage Schwann cell-derived plexiform neurofibromas (PN). Historically, little clinical success has been achieved targeting PN through surgery or chemotherapies. I performed an shRNA library screen of patient-derived Schwann cell lines to identify novel therapeutic targets to disrupt PN formation and progression. An shRNA library screen of human kinases and Rho-GTPases was performed in NF1-/- and paired NF1 competent immortalized Schwann cell lines. Following sequencing, candidates were identified. We previously developed a novel mouse model of NF1 wherein a neural crest specific Postncre targeted loxp-flanked Nf1 that replicated the PN found in patients. Additional cohorts of mice were generated with biallelic deletion of Rac1 (Nf1f/fRac1f/f Postn-Cre+; DKO ). Mice were aged for 9 months and peripheral nerves were harvested and fixed in formalin. Peripheral nerve size was measured and tumors were identified through blinded analysis of hematoxylin and eosin and Masson’s Trichrome (collagen) stained slides. Rho family members, including RAC1, were identified as candidates through an shRNA library screen. Genetic disruption of Rac1 in the Schwann cell lineage resulted in the prevention of tumor formation in DKO mice, as observed by peripheral nerve size and histological analysis. I observed an average of 14.8 +/- 2.65 tumors per mouse in the Nf1f/f Postnviii Cre+ cohort compared to 0 tumors in the DKO (p<0.0001). Following an shRNA library screen, RAC1 was identified as a candidate to modulate PN formation. Biallelic deletion of Rac1 in vivo prevented PN formation. I demonstrate that a candidate identified in an shRNA library screen can translate to an biological effect in a mouse model of PN.