Browsing by Subject "Neurofibromatosis 1"

Now showing 1 - 7 of 7
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    Dystrophic spinal deformities in a neurofibromatosis type 1 murine model
    (PLoS, 2015-03-18) Rhodes, Steven D.; Zhang, Wei; Yang, Dalong; Yang, Hao; Chen, Shi; Wu, Xiahoua; Yang, Xianlin; Mohammad, Khalid S.; Guise, Theresa A.; Bergner, Amanda L.; Stevenson, David A.; Yang, Feng-Chun; Department of Anatomy and Cell Biology, IU School of Medicine
    Despite the high prevalence and significant morbidity of spinal anomalies in neurofibromatosis type 1 (NF1), the pathogenesis of these defects remains largely unknown. Here, we present two murine models: Nf1flox/-;PeriCre and Nf1flox/-;Col.2.3Cre mice, which recapitulate spinal deformities seen in the human disease. Dynamic histomorphometry and microtomographic studies show recalcitrant bone remodeling and distorted bone microarchitecture within the vertebral spine of Nf1flox/-;PeriCre and Nf1flox/-;Col2.3Cre mice, with analogous histological features present in a human patient with dystrophic scoliosis. Intriguingly, 36-60% of Nf1flox/-;PeriCre and Nf1flox/-;Col2.3Cre mice exhibit segmental vertebral fusion anomalies with boney obliteration of the intervertebral disc (IVD). While analogous findings have not yet been reported in the NF1 patient population, we herein present two case reports of IVD defects and interarticular vertebral fusion in patients with NF1. Collectively, these data provide novel insights regarding the pathophysiology of dystrophic spinal anomalies in NF1, and provide impetus for future radiographic analyses of larger patient cohorts to determine whether IVD and vertebral fusion defects may have been previously overlooked or underreported in the NF1 patient population.
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    Existing and Developing Preclinical Models for Neurofibromatosis Type 1–Related Cutaneous Neurofibromas
    (Elsevier, 2023) Staedtke, Verena; Topilko, Piotr; Le, Lu Q.; Grimes, Kevin; Largaespada, David A.; Cagan, Ross L.; Steensma, Matthew R.; Stemmer-Rachamimov, Anat; Blakeley, Jaishri O.; Rhodes, Steven D.; Ly, Ina; Romo, Carlos G.; Lee, Sang Y.; Serra, Eduard; Pediatrics, School of Medicine
    Neurofibromatosis type 1 (NF1) is caused by a nonfunctional copy of the NF1 tumor suppressor gene that predisposes patients to the development of cutaneous neurofibromas (cNFs), the skin tumor that is the hallmark of this condition. Innumerable benign cNFs, each appearing by an independent somatic inactivation of the remaining functional NF1 allele, form in nearly all patients with NF1. One of the limitations in developing a treatment for cNFs is an incomplete understanding of the underlying pathophysiology and limitations in experimental modeling. Recent advances in preclinical in vitro and in vivo modeling have substantially enhanced our understanding of cNF biology and created unprecedented opportunities for therapeutic discovery. We discuss the current state of cNF preclinical in vitro and in vivo model systems, including two- and three-dimensional cell cultures, organoids, genetically engineered mice, patient-derived xenografts, and porcine models. We highlight the models' relationship to human cNFs and how they can be used to gain insight into cNF development and therapeutic discovery.
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    Hyperactive Ras/MAPK signaling is critical for tibial nonunion fracture in neurofibromin-deficient mice
    (Oxford University Press, 2013-12-01) Sharma, Richa; Wu, Xiaohua; Rhodes, Steven D.; Chen, Shi; He, Yongzheng; Yuan, Jin; Li, Jiliang; Yang, Xianlin; Li, Xiaohong; Jiang, Li; Kim, Edward T.; Stevenson, David A.; Viskochil, David; Xu, Mingjiang; Yang, Feng-Chun; Department of Pediatrics, IU School of Medicine
    Neurofibromatosis type 1 (NF1) is a common genetic disorder affecting 1 in 3500 individuals. Patients with NF1 are predisposed to debilitating skeletal manifestations, including osteopenia/osteoporosis and long bone pseudarthrosis (nonunion fracture). Hyperactivation of the Ras/mitogen-activated protein kinase (MAPK) pathway in NF1 is known to underlie aberrant proliferation and differentiation in cell lineages, including osteoclast progenitors and mesenchymal stem cells (MSCs) also known as osteoblast progenitors (pro-OBLs). Our current study demonstrates the hyper Ras/MAPK as a critical pathway underlying the pathogenesis of NF1-associated fracture repair deficits. Nf1-deficient pro-OBLs exhibit Ras/MAPK hyperactivation. Introduction of the NF1 GTPase activating-related domain (NF1 GAP-related domain) in vitro is sufficient to rescue hyper Ras activity and enhance osteoblast (OBL) differentiation in Nf1−/− pro-OBLs and NF1 human (h) MSCs cultured from NF1 patients with skeletal abnormalities, including pseudarthrosis or scoliosis. Pharmacologic inhibition of mitogen-activated protein kinase kinase (MEK) signaling with PD98059 partially rescues aberrant Erk activation while enhancing OBL differentiation and expression of OBL markers, osterix and osteocalcin, in Nf1-deficient murine pro-OBLs. Similarly, MEK inhibition enhances OBL differentiation of hMSCs. In addition, PD98059 rescues aberrant osteoclast maturation in Nf1 haploinsufficient bone marrow mononuclear cells (BMMNCs). Importantly, MEK inhibitor significantly improves fracture healing in an NF1 murine model, Col2.3Cre
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    Imatinib mesylate for plexiform neurofibromas in patients with neurofibromatosis type 1: a phase 2 trial
    (Elsevier, 2012-12) Robertson, Kent A.; Nalepa, Grzegorz; Yang, Feng-Chun; Bowers, Daniel C.; Ho, Chang Y.; Hutchins, Gary D.; Croop, James M.; Vik, Terry A.; Denne, Scott C.; Parada, Luis F.; Hingtgen, Cynthia M.; Walsh, Laurence E.; Yu, Menggang; Pradhan, Kamnesh R.; Edwards-Brown, Mary K.; Cohen, Mervyn D.; Fletcher, James W.; Travers, Jeffrey B.; Staser, Karl W.; Lee, Melissa W.; Sherman, Marcie R.; Davis, Cynthia J.; Miller, Lucy C.; Ingram, David A.; Clapp, D. Wade; Pediatrics, School of Medicine
    BACKGROUND: Plexiform neurofibromas are slow-growing chemoradiotherapy-resistant tumours arising in patients with neurofibromatosis type 1 (NF1). Currently, there are no viable therapeutic options for patients with plexiform neurofibromas that cannot be surgically removed because of their proximity to vital body structures. We undertook an open-label phase 2 trial to test whether treatment with imatinib mesylate can decrease the volume burden of clinically significant plexiform neurofibromas in patients with NF1. METHODS: Eligible patients had to be aged 3-65 years, and to have NF1 and a clinically significant plexiform neurofibroma. Patients were treated with daily oral imatinib mesylate at 220 mg/m(2) twice a day for children and 400 mg twice a day for adults for 6 months. The primary endpoint was a 20% or more reduction in plexiform size by sequential volumetric MRI imaging. Clinical data were analysed on an intention-to-treat basis; a secondary analysis was also done for those patients able to take imatinib mesylate for 6 months. This trial is registered with ClinicalTrials.gov, number NCT01673009. FINDINGS: Six of 36 patients (17%, 95% CI 6-33), enrolled on an intention-to-treat basis, had an objective response to imatinib mesylate, with a 20% or more decrease in tumour volume. Of the 23 patients who received imatinib mesylate for at least 6 months, six (26%, 95% CI 10-48) had a 20% or more decrease in volume of one or more plexiform tumours. The most common adverse events were skin rash (five patients) and oedema with weight gain (six). More serious adverse events included reversible grade 3 neutropenia (two), grade 4 hyperglycaemia (one), and grade 4 increases in aminotransferase concentrations (one). INTERPRETATION: Imatinib mesylate could be used to treat plexiform neurofibromas in patients with NF1. A multi-institutional clinical trial is warranted to confirm these results.
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    Nf1+/- monocytes/macrophages induce neointima formation via CCR2 activation
    (Oxford University Press, 2016-03-15) Bessler, Waylan K.; Kim, Grace; Hudson, Farlyn Z.; Mund, Julie A.; Mali, Raghuveer; Menon, Keshav; Kapur, Reuben; Clapp, D. Wade; Ingram Jr., David A.; Stansfield, Brian K.; Department of Pediatrics, IU School of Medicine
    Persons with neurofibromatosis type 1 (NF1) have a predisposition for premature and severe arterial stenosis. Mutations in the NF1 gene result in decreased expression of neurofibromin, a negative regulator of p21(Ras), and increases Ras signaling. Heterozygous Nf1 (Nf1(+/-)) mice develop a marked arterial stenosis characterized by proliferating smooth muscle cells (SMCs) and a predominance of infiltrating macrophages, which closely resembles arterial lesions from NF1 patients. Interestingly, lineage-restricted inactivation of a single Nf1 allele in monocytes/macrophages is sufficient to recapitulate the phenotype observed in Nf1(+/-) mice and to mobilize proinflammatory CCR2+ monocytes into the peripheral blood. Therefore, we hypothesized that CCR2 receptor activation by its primary ligand monocyte chemotactic protein-1 (MCP-1) is critical for monocyte infiltration into the arterial wall and neointima formation in Nf1(+/-) mice. MCP-1 induces a dose-responsive increase in Nf1(+/-) macrophage migration and proliferation that corresponds with activation of multiple Ras kinases. In addition, Nf1(+/-) SMCs, which express CCR2, demonstrate an enhanced proliferative response to MCP-1 when compared with WT SMCs. To interrogate the role of CCR2 activation on Nf1(+/-) neointima formation, we induced neointima formation by carotid artery ligation in Nf1(+/-) and WT mice with genetic deletion of either MCP1 or CCR2. Loss of MCP-1 or CCR2 expression effectively inhibited Nf1(+/-) neointima formation and reduced macrophage content in the arterial wall. Finally, administration of a CCR2 antagonist significantly reduced Nf1(+/-) neointima formation. These studies identify MCP-1 as a potent chemokine for Nf1(+/-) monocytes/macrophages and CCR2 as a viable therapeutic target for NF1 arterial stenosis.
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    RAS Signaling Gone Awry in the Skin: The Complex Role of RAS in Cutaneous Neurofibroma Pathogenesis, Emerging Biological Insights
    (Elsevier, 2023) Rhodes, Steven D.; McCormick, Frank; Cagan, Ross L.; Bakker, Annette; Staedtke, Verena; Ly, Ina; Steensma, Matthew R.; Lee, Sang Y.; Romo, Carlos G.; Blakeley, Jaishri O.; Sarin, Kavita Y.; Pediatrics, School of Medicine
    Cutaneous neurofibromas (cNFs) are the most common tumor in people with the rasopathy neurofibromatosis type 1. They number in hundreds or even thousands throughout the body, and currently, there are no effective interventions to prevent or treat these skin tumors. To facilitate the identification of novel and effective therapies, essential studies including a more refined understanding of cNF biology and the role of RAS signaling and downstream effector pathways responsible for cNF initiation, growth, and maintenance are needed. This review highlights the current state of knowledge of RAS signaling in cNF pathogenesis and therapeutic development for cNF treatment.
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    Ras-Mek-Erk Signaling Regulates Nf1 Heterozygous Neointima Formation
    (Elsevier B.V., 2014-01) Stansfield, Brian K.; Bessler, Waylan K.; Mali, Raghuveer; Mund, Julie A.; Downing, Brandon D.; Kapur, Reuben; Ingram, David A. Jr; Department of Pediatrics, IU School of Medicine
    Neurofibromatosis type 1 (NF1) results from mutations in the NF1 tumor-suppressor gene, which encodes neurofibromin, a negative regulator of diverse Ras signaling cascades. Arterial stenosis is a nonneoplastic manifestation of NF1 that predisposes some patients to debilitating morbidity and sudden death. Recent murine studies demonstrate that Nf1 heterozygosity (Nf1+/−) in monocytes/macrophages significantly enhances intimal proliferation after arterial injury. However, the downstream Ras effector pathway responsible for this phenotype is unknown. Based on in vitro assays demonstrating enhanced extracellular signal-related kinase (Erk) signaling in Nf1+/− macrophages and vascular smooth muscle cells and in vivo evidence of Erk amplification without alteration of phosphatidylinositol 3-kinase signaling in Nf1+/− neointimas, we tested the hypothesis that Ras-Erk signaling regulates intimal proliferation in a murine model of NF1 arterial stenosis. By using a well-established in vivo model of inflammatory cell migration and standard cell culture, neurofibromin-deficient macrophages demonstrate enhanced sensitivity to growth factor stimulation in vivo and in vitro, which is significantly diminished in the presence of PD0325901, a specific inhibitor of Ras-Erk signaling in phase 2 clinical trials for cancer. After carotid artery injury, Nf1+/− mice demonstrated increased intimal proliferation compared with wild-type mice. Daily administration of PD0325901 significantly reduced Nf1+/− neointima formation to levels of wild-type mice. These studies identify the Ras-Erk pathway in neurofibromin-deficient macrophages as the aberrant pathway responsible for enhanced neointima formation.