Browsing by Author "Ratner, Nancy"

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    A Collaborative Model for Accelerating the Discovery and Translation of Cancer Therapies
    (American Association for Cancer Research, 2017-11-01) Maertens, Ophélia; McCurrach, Mila E.; Braun, Benjamin S.; De Raedt, Thomas; Epstein, Inbal; Huang, Tannie Q.; Lauchle, Jennifer O.; Lee, Hyerim; Wu, Jianqiang; Cripe, Timothy P.; Clapp, D. Wade; Ratner, Nancy; Shannon, Kevin; Cichowski, Karen; Pediatrics, School of Medicine
    Preclinical studies using genetically engineered mouse models (GEMM) have the potential to expedite the development of effective new therapies; however, they are not routinely integrated into drug development pipelines. GEMMs may be particularly valuable for investigating treatments for less common cancers, which frequently lack alternative faithful models. Here, we describe a multicenter cooperative group that has successfully leveraged the expertise and resources from philanthropic foundations, academia, and industry to advance therapeutic discovery and translation using GEMMs as a preclinical platform. This effort, known as the Neurofibromatosis Preclinical Consortium (NFPC), was established to accelerate new treatments for tumors associated with neurofibromatosis type 1 (NF1). At its inception, there were no effective treatments for NF1 and few promising approaches on the horizon. Since 2008, participating laboratories have conducted 95 preclinical trials of 38 drugs or combinations through collaborations with 18 pharmaceutical companies. Importantly, these studies have identified 13 therapeutic targets, which have inspired 16 clinical trials. This review outlines the opportunities and challenges of building this type of consortium and highlights how it can accelerate clinical translation. We believe that this strategy of foundation-academic-industry partnering is generally applicable to many diseases and has the potential to markedly improve the success of therapeutic development.
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    CTF Meeting 2012: Translation of the Basic Understanding of the Biology and Genetics of NF1, NF2, and Schwannomatosis Toward the Development of Effective Therapies
    (Wiley, 2014) Widemann, Brigitte C.; Acosta, Maria T.; Ammoun, Sylvia; Belzberg, Allan J.; Bernards, Andre; Blakeley, Jaishri; Bretscher, Antony; Cichowski, Karen; Clapp, D. Wade; Dombi, Eva; Evans, Gareth D.; Ferner, Rosalie; Fernandez-Valle, Cristina; Fisher, Michael J.; Giovannini, Marco; Gutmann, David H.; Hanemann, C. Oliver; Hennigan, Robert; Huson, Susan; Ingram, David; Kissil, Joe; Korf, Bruce R.; Legius, Eric; Packer, Roger J.; McClatchey, Andrea I.; McCormick, Frank; North, Kathryn; Pehrsson, Minja; Plotkin, Scott R.; Ramesh, Vijaya; Ratner, Nancy; Schirmer, Susann; Sherman, Larry; Schorry, Elizabeth; Stevenson, David; Stewart, Douglas R.; Ullrich, Nicole; Bakker, Annette C.; Morrison, Helen; Medicine, School of Medicine
    The neurofibromatoses (NF) are autosomal dominant genetic disorders that encompass the rare diseases NF1, NF2, and schwannomatosis. The NFs affect more people worldwide than Duchenne muscular dystrophy and Huntington's disease combined. NF1 and NF2 are caused by mutations of known tumor suppressor genes (NF1 and NF2, respectively). For schwannomatosis, although mutations in SMARCB1 were identified in a subpopulation of schwannomatosis patients, additional causative gene mutations are still to be discovered. Individuals with NF1 may demonstrate manifestations in multiple organ systems, including tumors of the nervous system, learning disabilities, and physical disfigurement. NF2 ultimately can cause deafness, cranial nerve deficits, and additional severe morbidities caused by tumors of the nervous system. Unmanageable pain is a key finding in patients with schwannomatosis. Although today there is no marketed treatment for NF-related tumors, a significant number of clinical trials have become available. In addition, significant preclinical efforts have led to a more rational selection of potential drug candidates for NF trials. An important element in fueling this progress is the sharing of knowledge. For over 20 years the Children's Tumor Foundation has convened an annual NF Conference, bringing together NF professionals to share novel findings, ideas, and build collaborations. The 2012 NF Conference held in New Orleans hosted over 350 NF researchers and clinicians. This article provides a synthesis of the highlights presented at the conference and as such, is a "state-of-the-field" for NF research in 2012.
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    A molecular basis for neurofibroma-associated skeletal manifestations in NF1
    (Elsevier, 2020-11) Ma, Yun; Gross, Andrea; Dombi, Eva; Pemov, Alex; Choi, Kwangmin; Chaney, Katherine; Rhodes, Steven D.; Angus, Steven P.; Sciaky, Noah; Clapp, D. Wade; Ratner, Nancy; Widemann, Brigitte C.; Rios, Jonathan J.; Elefteriou, Florent; Pediatrics, School of Medicine
    Purpose: Plexiform neurofibromas (pNF) develop in children with neurofibromatosis type 1 (NF1) and can be associated with several skeletal comorbidities. Preclinical mouse studies revealed Nf1 deficiency in osteoprogenitor cells disrupts, in a MEK-dependent manner, pyrophosphate (PPi) homeostasis and skeletal mineralization. The etiology of NF-associated skeletal manifestations remains unknown. Methods: We used mouse models of NF1 neurofibromas to assess bone mineralization of skeletal structures adjacent to tumors. Expression of genes involved in pyrophosphate homeostasis was assessed in mouse and human NF tumors and Schwann cell cultures. We used dual-energy X-ray absorptiometry (DXA) to assess tumor-associated changes in bone mineral density (BMD) in an individual with NF1 following treatment with the MEK inhibitor selumetinib. Results: We detected increased nonmineralized bone surfaces adjacent to tumors in mouse models of NF1 neurofibromas. Expression of Enpp1, a PPi-generating ectophosphatase, and ANKH, a PPi transporter, was increased in mouse and human neurofibroma-derived tissues and Schwann cells, respectively. In one patient, tumor-associated reductions in BMD were partially rescued following therapy with selumetinib. Conclusion: Results indicate that NF-associated skeletal pathologies in NF1 are associated with dysregulated pyrophosphate homeostasis in adjacent NF tumors and suggest that treatment of NFs with MEK inhibitors may improve skeletal manifestations of the disease.
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    Neurofibromin-deficient Schwann cells secrete a potent migratory stimulus for Nf1+/– mast cells
    (2003-12) Yang, Feng-Chun; Ingram, David A; Chen, Shi; Hingtgen, Cynthia M; Ratner, Nancy; Monk, Kelly R; Clegg, Travis; White, Hilary; Mead, Laura; Wenning, Mary Jo; Williams, David A; Kapur, Reuben; Atkinson, Simon J; Clapp, D Wade
    The NF1 tumor suppressor gene encodes a GTPase-activating protein called neurofibromin that negatively regulates Ras signaling. Mutations in NF1 cause neurofibromatosis type 1 (NF1). The development of neurofibromas, which are complex tumors composed of multiple cell types, is a hallmark of NF1. Somatic inactivation of murine Nf1 in Schwann cells is necessary, but not sufficient, to initiate neurofibroma formation. Neurofibromas occur with high penetrance in mice in which Nf1 is ablated in Schwann cells in the context of a heterozygous mutant (Nf1+/–) microenvironment. Mast cells infiltrate neurofibromas, where they secrete proteins that can remodel the ECM and initiate angiogenesis. Thus, identification of mechanisms responsible for mast cell migration to tumor microenvironments is important for understanding tumorigenesis and for designing potential therapies. Here, we show that homozygous Nf1 mutant (Nf1–/–) Schwann cells secrete Kit ligand (KitL), which stimulates mast cell migration, and that Nf1+/– mast cells are hypermotile in response to KitL. Furthermore, we link hyperactivation of the Ras-class IA-PI3K-Rac2 pathway to increased Nf1+/– mast cell migration. Thus, these studies identify a novel interaction between Nf1–/– Schwann cells and Nf1+/– mast cells that is likely to be important in neurofibroma formation.
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    Preclinical assessments of the MEK inhibitor PD-0325901 in a mouse model of neurofibromatosis type 1.
    (Wiley, 2015-10) Jousma, Edwin; Rizvi, Tilat A.; Wu, Jianqiang; Janhofer, David; Dombi, Eva; Dunn, Richard S.; Kim, Mi-Ok; Masters, Andrea R.; Jones, David R.; Cripe, Timothy P.; Ratner, Nancy; Department of Medicine, IU School of Medicine
    Background: Neurofibromatosis type 1 (NF1) is a genetic disorder that predisposes affected individuals to formation of benign neurofibromas, peripheral nerve tumors that can be associated with significant morbidity. Loss of the NF1 Ras-GAP protein causes increased Ras-GTP, and we previously found that inhibiting MEK signaling downstream of Ras can shrink established neurofibromas in a genetically engineered murine model. Procedures: We studied effects of MEK inhibition using 1.5 mg/kg/day PD-0325901 prior to neurofibroma onset in the Nf1 flox/flox;Dhh-Cre mouse model. We also treated mice with established tumors at 0.5 and 1.5 mg/kg/day dosees of PD-0325901. We monitored tumor volumes using MRI and volumetric measurements, and measured pharmacokinetic and pharmacodynamic endpoints. Results: Early administration significantly delayed neurofibroma development as compared to vehicle controls. When treatment was discontinued neurofibromas grew, but no rebound effect was observed and neurofibromas remained significantly smaller than controls. Low dose treatment of mice with PD-0325901 resulted in neurofibroma shrinkage equivalent to that observed at higher doses. Tumor cell proliferation decreased, although less than at higher doses with drug. Tumor blood vessels per area correlated with tumor shrinkage. Conclusions: Neurofibroma development was not prevented by MEK inhibition, beginning at 1 month of age, but tumor size was controlled by early treatment. Moreover, treatment with PD-0325901 at very low doses may shrink neurofibromas while minimizing toxicity. These studies highlight how genetically engineered mouse models can guide clinical trial design.