SCF (SKP1-Cullins-F box protein) E3 ubiquitin ligase is the largest family of E3 ligases that promote the ubiquitylation and degradation of various key regulatory proteins, thus controlling many important biological processes, such as apoptosis, cell cycle progression, DNA replication, embryogenesis and tumorigenesis. SCF consists of 4 components, including a scaffold protein cullin-1, an adaptor protein SKP1, a RING protein RBX1 or RBX2 and an F-box protein. The F-box protein with 69 members in mammalian cells is the substrate- recognizing subunit that determines the specificity of SCF E3s. While a variety of protein substrates have been identified by one of well-characterized F-box proteins TrCP, FBXW7, or SKP2, very little is known as to whether and how F-box proteins regulate each other. Our preliminary data showed that 1) oncogenic F-box protein ?TrCP binds to yet a poorly characterized F-box protein FBXW2 to promote its ubiquitylation and degradation; 2) FBXW2 in turn binds to oncogenic F-box protein SKP2 to promote its ubiquitylation and degradation; 3) FBXW2 has tumor suppressive function against lung cancer cells; 4) A number of gain-of- function FBXW2 mutations were found in human non-small cell lung carcinoma tissues; and 5) reversed correlation in expression among ?-TrCP, FBXW2 and SKP2 exists in lung cancer tissues, which is associated with patient survival. Although ?-TrCP and SKP2 are well-studied F-box proteins with oncogenic activity, whether and how they regulate each other with regard to cell proliferation and survival is totally unknown. The objectives of this proposed study is to understand how FBXW2 mediates and modulates the activity of two well-known oncogenic F-box proteins, ?-TrCP and SKP2, and how FBXW2 acts as a novel tumor suppressor in lung tumorigenesis using both in vitro cell culture and in vivo genetically modified mouse models with elucidation of its mechanism of action. The central hypothesis is that three F- box proteins, ?TrCP-FBXW2-SKP2 form an oncogene-tumor suppressor-oncogene axis that regulates each other to control cell proliferation and lung tumorigenesis.
Three specific aims are proposed to test our central hypothesis by 1) characterizing FBXW2 as a novel substrate of ?-TRCP; 2) characterizing FBXW2 as a novel E3 ligase for SKP2 degradation; and 3) characterizing Fbxw2 as a novel tumor suppressor against lung tumorigenesis. Relevance: Successful completion of this proposed study will mechanistically elucidate how three F-box proteins regulate proliferation of lung cancer cells by targeting each other for degradation, and how two oncogenic F-box proteins -TrCP and SKP2 talk with each other via a tumor suppressive F-box protein FBXW2, and how FBXW2 acts as a tumor suppressor in the lung, thus elucidating a novel mechanism of lung tumorigenesis and providing attractive targets for future biomarker development in lung cancer management.

Public Health Relevance

F-box proteins are substrate-recognizing components of SCF E3 ubiquitin ligases which promote ubiquitylation and degradation of key signal molecules. How F-box proteins cross-talk with each other to affect lung tumorigenesis is unknown. In this study, we will mechanistically elucidate how the F-box axis, ?TrCP-FBXW2-SKP2 regulates growth and survival of lung cancer cells by targeted degradation of each other, and how Fbxw2, a poorly characterized F-box protein, act as a tumor suppressor to inhibit lung tumorigenesis triggered by Kras. Our study will elucidate a novel mechanism of lung tumorigenesis, thus providing attractive targets for biomarker development in the management of lung cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA156744-07
Application #
9248902
Study Section
Molecular Oncogenesis Study Section (MONC)
Program Officer
Strasburger, Jennifer
Project Start
2011-05-11
Project End
2021-03-31
Budget Start
2017-04-01
Budget End
2018-03-31
Support Year
7
Fiscal Year
2017
Total Cost
$331,312
Indirect Cost
$117,562
Name
University of Michigan Ann Arbor
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Li, Hua; Zhou, Weihua; Li, Lihui et al. (2017) Inhibition of Neddylation Modification Sensitizes Pancreatic Cancer Cells to Gemcitabine. Neoplasia 19:509-518
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Kuang, Peng; Tan, Mingjia; Zhou, Weihua et al. (2016) SAG/RBX2 E3 ligase complexes with UBCH10 and UBE2S E2s to ubiquitylate ?-TrCP1 via K11-linkage for degradation. Sci Rep 6:37441
Zhang, Qiang; Karnak, David; Tan, Mingjia et al. (2016) FBXW7 Facilitates Nonhomologous End-Joining via K63-Linked Polyubiquitylation of XRCC4. Mol Cell 61:419-433
Lan, Huiyin; Tang, Zaiming; Jin, Hongchuan et al. (2016) Neddylation inhibitor MLN4924 suppresses growth and migration of human gastric cancer cells. Sci Rep 6:24218
Zhou, Xiaochen; Tan, Mingjia; Nyati, Mukesh K et al. (2016) Blockage of neddylation modification stimulates tumor sphere formation in vitro and stem cell differentiation and wound healing in vivo. Proc Natl Acad Sci U S A 113:E2935-44

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