Identification of NPM and DDX5 as Therapeutic Targets in TSC
Abstract
Can we find a targeted treatment, other than mTOR inhibition, that can be utilized in tuberous sclerosis complex (TSC) patients? This question has remained at the top of the list for many clinicians, researchers, and patients. TSC is a common inherited predisposition syndrome, affecting nearly 1 in 7,500 individuals. Individuals with TSC develop benign tumors in multiple organs, including the retina, skin, lung, kidney, and brain. However, these lesions can present as malignant. TSC results from mutations in either the TSC1 or TSC2 gene, resulting in hyperactivation of the mTOR-signaling pathway. This pathway ultimately controls downstream effectors of cellular mRNA translation and proliferation. Multiple studies in mice have demonstrated the requirement of mTOR activity for aberrant TSC cell growth in vitro and in vivo, and these initial findings have translated to human cells as well with drugs that target mTOR (rapamycin and its analogues) as the first line of clinical trials aimed at treating TSC. However, the identification of other valid targets in TSC has been discouraging, leaving the field to concentrate on rapamycin and its analogues as the sole treatment for TSC. In search of additional TSC targets, we recently identified NPM as a downstream effector of mTOR signaling in TSC cells, providing cells with an abundant supply of ribosomes necessary for supporting their increased growth rate. We now provide evidence that NPM forms a novel complex with DDX5 to drive TSC cell growth. Targeting this interaction might provide a novel treatment strategy for TSC patients. We have developed a novel split-firefly luciferase reporter construct that accurately measures the formation of NPM-DDX5 oncogenic complexes in living cells. We have successfully expressed this reporter in human and mouse TSC cells. In this setting, we observe robust luciferase luminescence signals, indicating the formation of NPM-DDX5 complexes. Importantly, this reporter can be used in a pharmacological high-throughput manner with robotics to speed discovery. In our proposal, this reporter will be used to screen two chemical libraries for inhibitors of NPM-DDX5 complex formation. As inhibitors of the NPM-DDX5 complex in TSC cells, these unique compounds should possess growth inhibitory properties in a variety of TSC cells, thus providing an innovative new approach to treating TSC. We hypothesize that aberrant NPM-DDX5 complexes formed in TSC cells can be pharmacologically targeted to prevent TSC cellular proliferation. Our combined expertise in tumor suppressors and oncogenes along with our unlimited access to the High-Throughput Screening Center at Washington University gives us tremendous leverage in successfully screening over 16,000 chemical compounds that inhibit NPM-DDX5 complexes and TSC cell proliferation. We have recruited key collaborators to insure that we perform high-risk, yet sound experiments that are the most relevant to current TSC patients. Our work will identify new compounds that might be used clinically in the treatment of TSC. How fast can we get there? Our 2-year proposal should uncover lead compounds that can be used in preclinical TSC animal models with the hope that positive animal results will lead to Phase 0/I human trials.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 04, 2016
- Source ID
- W81XWH1510528
Entities
People
- Jason D Weber
Organizations
- United States Army
- Washington University in St. Louis