Nore1a is a member of the RASSF family of tumor suppressors. It is frequently down- regulated in primary human tumors and is genetically linked to a familial human cancer syndrome. Over-expression of Nore1a can promote apoptosis, cell cycle arrest and senescence. Restoration of Nore1a expression to physiological levels blocks the tumorigenic phenotype and shRNA mediated inactivation of Nore1a enhances the transformed phenotype. Thus, the evidence that Nore1a is an important human tumor suppressor is strong. Nore1a also directly binds the Ras oncoprotein and appears to serve as a novel effector, mediating some of the pro-apoptotic and pro-senescent effects of oncogenic Ras. Thus, loss of function of Nore1a may be particularly important to Ras dependent tumors, allowing oncogenic Ras to circumvent its apoptotic and senescent functions. However, the signaling pathways controlled by Nore1a have not been defined, and no animal model for Nore1a function has been investigated. Furthermore, the effects of loss of Nore1a function on the transforming effects of oncogenic Ras have not been characterized. Nore1a lacks obvious enzymatic activity, and little is known about its mechanism of action. However, it has been hypothesized that it may serve as a scaffolding protein to modulate the formation of tumor suppressor complexes. We have now identified two tumor suppressors in endogenous complex with Nore1a: the Homeodomain Interacting Protein Kinase 2 (HIPK2) protein and the Von Hippel-Lindau protein (VHL), a notorious tumor suppressor which plays a critical role in the development of the majority of Renal Cell Carcinomas (RCC). Both HIPK2 and VHL act, in part, by directly modulating the master tumor suppressor p53. Defects in p53 have been detected in approximately 50% of human tumors, and it may be argued that p53 is the most critical tumor suppressor yet identified. Thus, Nore1a may function by modulating p53 by dual pathways and could serve as part of the well known, but poorly characterized, link between Ras and p53. We propose a series of experimental aims designed to determine the precise role of Nore1a loss of function in the development of the tumorigenic phenotype and in Ras mediated transformation. This includes a proposal to determine the role of the Nore1a/Ras interaction in vivo, using a novel Nore1a knockout mouse model. We will then determine if the mechanism of action of Nore1a involves the modulation of the HIPK2 or VHL tumor suppressors, and whether Nore1a acts to integrate their effects upon p53. We anticipate that these experiments will identify Nore1a as an important novel diagnostic and therapeutic target for cancer.

Public Health Relevance

These studies will serve to define the role of a novel potential tumor suppressor, Nore1a, in human cancer. They will determine if Nore1a is an important diagnostic/prognostic marker for cancer. They will also determine if Nore1a may be a suitable candidate for the development of epigenetic therapy to restore its normal function in tumor cells.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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Cancer Molecular Pathobiology Study Section (CAMP)
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Watson, Joanna M
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University of Louisville
Internal Medicine/Medicine
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United States
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Schmidt, M Lee; Hobbing, Katharine R; Donninger, Howard et al. (2018) RASSF1A Deficiency Enhances RAS-Driven Lung Tumorigenesis. Cancer Res 78:2614-2623
Barnoud, Thibaut; Schmidt, M Lee; Donninger, Howard et al. (2017) The role of the NORE1A tumor suppressor in Oncogene-Induced Senescence. Cancer Lett 400:30-36
Arora, Payal; Basu, Amartya; Schmidt, M Lee et al. (2017) Nonstructural protein 5B promotes degradation of the NORE1A tumor suppressor to facilitate hepatitis C virus replication. Hepatology 65:1462-1477
Donninger, Howard; Barnoud, Thibaut; Clark, Geoffrey J (2016) NORE1A is a double barreled Ras senescence effector that activates p53 and Rb. Cell Cycle 15:2263-4
Schmidt, M Lee; Calvisi, Diego F; Clark, Geoffrey J (2016) NORE1A Regulates MDM2 Via ?-TrCP. Cancers (Basel) 8:
Donninger, Howard; Clark, Geoffrey J (2016) Nore1a drives Ras to flick the P53 senescence switch. Mol Cell Oncol 3:e1055050
Donninger, Howard; Schmidt, M Lee; Mezzanotte, Jessica et al. (2016) Ras signaling through RASSF proteins. Semin Cell Dev Biol 58:86-95
Barnoud, Thibaut; Donninger, Howard; Clark, Geoffrey J (2016) Ras Regulates Rb via NORE1A. J Biol Chem 291:3114-23
Donninger, Howard; Calvisi, Diego F; Barnoud, Thibaut et al. (2015) NORE1A is a Ras senescence effector that controls the apoptotic/senescent balance of p53 via HIPK2. J Cell Biol 208:777-89
Scherzer, Michael T; Waigel, Sabine; Donninger, Howard et al. (2015) Fibroblast-Derived Extracellular Matrices: An Alternative Cell Culture System That Increases Metastatic Cellular Properties. PLoS One 10:e0138065

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