Molecular Therapies for Tuberous Sclerosis and Neurofibromatosis
ABSTRACT Neurofibromatosis type 1 (NF1) and tuberous sclerosis complex (TSC) are autosomal-dominant genetic disorders that result from dysregulation of the PI3K/AKT/mammalian target of rapamycin (mTOR) pathway. NF1 is caused by mutations in the NF1 gene on chromosome 17q11.2. Its protein product, neurofibromin, functions as a tumor suppressor and ultimately produces constitutive upregulation of mTOR. TSC is caused by mutations in either the TSC1 (chromosome 9q34) or TSC2 (chromosome 16p.13.3) genes. Their protein products, hamartin and tuberin, respectively, form a dimer that acts via the GAP protein Rheb (Ras homolog enhanced in brain) to directly inhibit mTOR, again resulting in upregulation. Specific inhibitors of mTOR are in clinical use, including sirolimus, everolimus, temsirolimus, and deforolimus. Everolimus has been shown to reduce the volume and appearance of subependymal giant cell astrocytomas (SEGA), facial angiofibromas, and renal angiomyolipomas associated with TSC, with a recent FDA approval for SEGA not suitable for surgical resection. This article reviews the use of mTOR inhibitors in these diseases, which have the potential to be a disease-modifying therapy in these and other conditions.
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- "Therapies that target PI3K/AKT/mTOR and MAPK pathways have been of studied both pre-clinically and in clinical trials for many cancer types [4, 20, 21]. The most clinically studied are drugs that bind FKBP12, inhibiting the mammalian target of rapamycin pathway by directly binding the mTOR Complex1 (mTORC1), not inhibiting kinase activity directly . "
ABSTRACT: Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas that occur spontaneously, or from benign plexiform neurofibromas, in the context of the genetic disorder Neurofibromatosis Type 1 (NF1). The current standard treatment includes surgical resection, high-dose chemotherapy, and/or radiation. To date, most targeted therapies have failed to demonstrate effectiveness against plexiform neurofibromas and MPNSTs. Recently, several studies suggested that the mTOR and MAPK pathways are involved in the formation and progression of MPNSTs. Everolimus (RAD001) inhibits the mTOR and is currently FDA approved for several types of solid tumors. PD-0325901 (PD-901) inhibits MEK, a component of the MAPK pathway, and is currently in clinical trials. Here, we show in vitro than MPNST cell lines are more sensitive to inhibition of cellular growth by Everolimus and PD-901 than immortalized human Schwann cells. In combination, these drugs synergistically inhibit cell growth and induce apoptosis. In two genetically engineered mouse models of MPNST formation, modeling both sporadic and NF1-associated MPNSTs, Everolimus, or PD-901 treatment alone each transiently reduced tumor burden and size, and extended lifespan. However, prolonged treatment of each single agent resulted in the development of resistance and reactivation of target pathways. Combination therapy using Everolimus and PD-901 had synergistic effects on reducing tumor burden and size, and increased lifespan. Combination therapy allowed persistent and prolonged reduction in signaling through both pathways. These data suggest that co-targeting mTOR and MEK may be effective in patients with sporadic or NF1-associated MPNSTs.Oncotarget 01/2014; 5(6). · 6.63 Impact Factor
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ABSTRACT: Neurodevelopmental disorders (NDDs) are characterized by aberrant and delayed early-life development of the brain, leading to deficits in language, cognition, motor behaviour and other functional domains, often accompanied by somatic symptoms. Environmental factors like perinatal infection, malnutrition, trauma and poor parental care increase the risk of the heterogeneous, multifactorial and polygenic disorders, autism and schizophrenia. Conversely, discrete genetic anomalies are involved in Down, Rett and Fragile X syndromes, tuberculous sclerosis and neurofibromatosis, the less familiar Phelan-McDermid, Sotos, Kleefstra, Coffin-Lowry and "ATRX" syndromes, and the disorders of imprinting, Angelman and Prader-Willi syndromes. NDDs have been termed "synaptopathies" in reference to structural and functional disturbance of synaptic plasticity, several involve abnormal Ras-Kinase signaling ("rasopathies"), and many are characterized by disrupted cerebral connectivity and an imbalance between excitatory and inhibitory transmission. However, at a different level of integration, NDDs are accompanied by aberrant "epigenetic" regulation of processes critical for normal and orderly development of the brain. Epigenetics refers to potentially-heritable (by mitosis and/or meiosis) mechanisms controlling gene expression without changes in DNA sequence. In certain NDDs, prototypical epigenetic processes of DNA methylation and covalent histone marking are impacted. Conversely, others involve anomalies in chromatin-modelling, mRNA splicing/editing, mRNA translation, ribosome biogenesis and/or the regulatory actions of small nucleolar RNAs and micro-RNAs. Since epigenetic mechanisms are modifiable, this raises the hope of novel therapy, though questions remain concerning efficacy and safety. The above issues are critically surveyed in this review, which advocates a broad-based epigenetic framework for understanding and ultimately treating a diverse assemblage of NDDs ("epigenopathies") lying at the interface of genetic, developmental and environmental processes.Neuropharmacology 12/2012; 68. DOI:10.1016/j.neuropharm.2012.11.015 · 4.82 Impact Factor
- Actas Dermo-Sifiliográficas 01/2013; 105(8). DOI:10.1016/j.ad.2013.09.013