- Induced Pluripotent Stem Cells as Potential Therapeutic Agents in NF1
- Identification of the Cellular and Molecular Mechanisms Underlying the Osseous Manifestations of NF1 in Murine and Human Systems
- Characterizing KEN: A Novel NF2/Merlin Protein Complex Modulating Growth Control
- Identification of a New Target and Treatment Compound for NF1-Associated Cancer
Induced Pluripotent Stem Cells as Potential Therapeutic Agents in NF1
Posted November 23, 2010
Jonathan Chernoff, M.D., Ph.D., Fox Chase Cancer Center, Philadelphia, Pennsylvania
Exploration - Hypothesis Development Award, FY09
Although previous investigations have revealed signaling pathways regulated by the neurofibromatosis type 1 (NF1) protein, there are currently no effective medical therapies for the treatment of NF1. Individuals with NF1 may experience a variety of clinical manifestations including the development of neurofibromas, optic gliomas, skeletal abnormalities, and learning disabilities. NF1 tumors are composed of a mixture of Schwann cells, fibroblasts, perineural cells, and mast cells. In humans who inherit a mutant Nf1 allele, the second copy of the gene is lost in tumors, in the context of heterozygous loss in all other tissues. In mouse models of NF1, researchers have shown that this heterozygous background is essential for the development of disease. In particular, Nf1-heterozygous mast cells appear to play a vital role. Such mast cells are prone to migrate to the tumor site and secrete substances that facilitate Schwann cell growth. Thus, a potential therapeutic strategy is to repair the damaged Nf1 allele in mast cells. With funding from an FY09 Exploration - Hypothesis Development Award, Dr. Jonathan Chernoff, at the Fox Chase Cancer Center, will repair the defective Nf1 allele in induced pluripotent stem cells (iPS) derived from murine Nf1 heterozygote skin cells and will then transplant these cells into irradiated NF1 mice. By normalizing mast cells, it is anticipated that the outcomes of this research will demonstrate a reduction in the development of neurofibromas in NF1 mice and may provide a new method for the treatment of NF1.
Identification of the Cellular and Molecular Mechanisms Underlying the Osseous Manifestations of NF1 in Murine and Human Systems
Posted August 27, 2010
Feng-Chun Yang, M.D./Ph.D., Indiana University, Indianapolis, Indiana
Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder that is caused by mutations in the NF1 tumor suppressor gene. Approximately 50% of NF1 patients experience skeletal abnormalities/osseous manifestations (osteoporosis, kyphoscoliosis, pseudoarthrosis). The most prevalent of these skeletal abnormalities is kyphoscoliois (curvature of the spine), which often requires expensive multiple surgeries to avoid long-term complications such as restrictive lung disease, pain, and disfigurement. Although NF1 patients demonstrate a high incidence of skeletal abnormalities, the molecular mechanisms underlying the pathogenesis of skeletal abnormalities is unknown. As skeletal remodeling is controlled by interactions between osteoclasts and osteoblasts, Dr. Feng-Chun Yang, recipient of the 2007 Neurofibromatosis Research Program New Investigator Award, has developed genetic intercrosses using Nf1flox/flox mice and pre-osteoblasts and/or osteoblasts specific promoter(s) to model the different skeletal manifestations of NF1 patients including the reduction in somatic size, osteoporosis, scoliosis, and kyphoscoliosis. With funding from this award, Dr. Yang is using this mouse model to assess how Nf1 modifies osteoclast-osteoblast interactions, to identify potential molecular targets influencing these interactions and to determine the role of Nf1 in altering mesenchymal stem cell fate and investigating the impact of hematopoietic lineage on the skeletal deficits.
Data generated thus far reveal that these mice have increased osteoclast activity and reduced bone mineral density, calcium ossification, and bone turnover. Dr. Yang's group has also found that the mice with deficiency of Nf1 in osteoblasts and haploinsufficiency of hematopoietic lineage develop multiple skeletal defects, including short stature, osteoporosis, delayed fracture healing and kyphoscoliosis. This mouse model closely recapitulates the human NF1 osseous manifestations. Further investigation with this mouse model may provide a platform to understanding the molecular and cellular mechanisms that underlie the osseous manifestations of NF1 patients.
Characterizing KEN: A Novel NF2/Merlin Protein Complex Modulating Growth Control
Posted May 3, 2010
Duojia Pan, Ph.D., Johns Hopkins University School of Medicine and Howard Hughes Medical Institute, Baltimore, Maryland
A critical aspect of Neurofibromatosis Type 2 (NF2) research is the identification of downstream effector pathways regulated by the NF2/Merlin tumor suppressor protein. Previous investigations by Dr. Duojia Pan of Johns Hopkins University have identified Kibra, a novel tumor suppressor gene in Drosophila. Dr. Pan has also shown that Kibra, NF2/Merlin, and the related FERM domain protein Expanded (Ex) form a protein complex. The resulting Kibra, Ex, NF2/Merlin (KEN) complex regulates the Hippo pathway, a conserved signaling pathway involved in tissue homeostasis. Hippo signaling is modulated by several tumor suppressors, ultimately resulting in the phosphorylation and inactivation of the oncoprotein Yki (Drosophila)/YAP (mammals). Thus, the functional link between the KEN complex and the Hippo pathway may provide a potential mechanism by which NF2/Merlin functions as a tumor suppressor. With funding from a Fiscal Year 2009 Neurofibromatosis Research Program Investigator-Initiated Research Award, Dr. Pan proposes to further elucidate the molecular mechanism by which the NF2/Merlin tumor suppressor functions together with Ex and Kibra in the context of the Hippo signaling pathway, using Drosophila and mammalian cells as experimental models. This research could offer insight into how NF2/Merlin functions as a tumor suppressor protein, therefore leading, potentially, to better prevention and treatment of NF2.
Identification of a New Target and Treatment Compound for NF1-Associated Cancer
Posted March 25, 2010
David H. Gutmann, M.D., Ph.D., Neurofibromatosis Center, Washington University School of Medicine, St. Louis, Missouri
Tumors in the inherited cancer syndrome, neurofibromatosis type 1 (NF1) are characterized by the loss of function of the NF1 gene product, neurofibromin. Neurofibromin functions primarily as a negative regulator of the Ras proto-oncogene with further evidence identifying the mammalian target of rapamycin (mTOR) as being a critical downstream effector of neurofibromin/Ras-induced cell proliferation and tumorigenesis. Previous studies from Dr. David Gutmann's laboratory at the Washington University School of Medicine have identified that Rac1 activation is required for mTOR-dependent growth control.
As there are currently very few Rac1 specific inhibitors for preclinical/clinical study, Dr. Gutmann, with support from a fiscal year 2005 Investigator-Initiated Research Award through the Neurofibromatosis Research Program, explored an alternative approach to identifying new, potent anti-cancer compounds suitable for the treatment of NF1-associated brain tumors. Using an unbiased high-throughput chemical library screen of NF1-deficient malignant peripheral nerve sheath tumor (MPNST) cells, a novel compound, Cucurbitacin-I, was been selected for its cell growth inhibitory and pro-apoptotic effect. Since Cucurbitacin-I is known to inhibit signal transducer and activator of transcription-3 (STAT3) function in other cell types, Dr. Gutmann examined whether STAT3 could play a role in the growth of NF1-associated tumors and Nf1-deficient primary brain cells. Dr. Gutmann identified that neurofibromin negatively regulated STAT3 activity in vitro and in vivo, leading to STAT3 hyperactivation in NF1-deficient cells. Based on their findings, a model for neurofibromin cell growth regulation involving the mTOR/Rac1/STAT3 signaling pathway and the role of STAT3 in controlling transcription, apoptosis, and proliferation were also established. Excitingly, Cucurbitacin-I, via STAT3 inhibition, decreased NF1-deficient MPNST cell and tumor growth in vivo. These novel discoveries may ultimately lead to improved therapeutic approaches for the management of NF1-associated brain tumors.
Banerjee S, Byrd JN, Gianino SM, Harpstrite SE, Rodriguez FJ, Tuskan RG, Reilly KM, Piwnica-Worms DR, Gutmann DH. 2010. The neurofibromatosis type 1 tumor suppressor controls cell growth by regulating signal transducer and activator of transcription-3 activity in vitro and in vivo. Cancer Res 70(4):1356-1366.