Cancer metabolism has recently emerged to play an important role in cancer development and drug resistance. A key regulator involved in cancer metabolism is serine/threonine kinase LKB1. It displays a """"""""double-edged sword"""""""" role in cancer suppression and promotion and forms a heterotrimeric complex with two other proteins, the pseudokinase STRAD and the scaffolding protein MO25. Binding of LKB1 to these two protein promotes and stabilizes the activated conformation of LKB1. Although LKB1 has been shown to play a critical role in regulating cancer development, how LKB1 activation and activity are regulated is poorly defined. Our preliminary results revealed a novel mechanism by which LKB1 kinase activity is maintained. We showed LKB1 kinase activity is positively regulated by oncogenic Skp2, which forms a SCF complex with Skp1, Cul-1 and Rbx1 to constitute an E3 ligase. Interestingly, we found that Skp2 is a direct E3 ligase for LKB1, and Skp2-mediated ubiquitination of LKB1 is required for LKB1 activity. We hypothesized that K63-linked ubiquitination of LKB1 is essential for maintaining the integrity of LKB1-STRAD-MO25 complex, thereby regulating LKB1 activation. The goal of this study is to test this hypothetical model and to determine the role of this ubiquitination in cancer development. We will test our central hypothesis by pursuing three specific aims.
Aim 1. To characterize the role of Skp2-mediated K63-linked ubiquitination of LKB1 in LKB1 activity. Rationale.
Aim 2. To identify the role of LKB1 in regulating Akt signaling activation.
Aim 3. To explore the interplays between Skp2 and LKB1 in oncogenic functions. In summary, our study has several novel discoveries with important clinical implications. First, we showed for the first time that K63-linked ubiquitination of LKB1 i critical for LKB1 kinase activity. Second, we found that LKB1 is required for oncogenic Akt activation in response to EGF, thereby providing an insight and paradigm for oncogenic Akt activation. Third, we showed that Skp2 E3 ligase is an E3 ligase for LKB1, which is critical for LKB1 activation. Fourth, our study may offer a novel insight and mechanism for oncogenic Skp2 in cell transformation and tumorigenesis by activating the LKB1-AMPK-ACC pathway. Finally, our study may not only reveal novel oncogenic function and mechanism for LKB1 in tumor maintenance, but also help identify LKB1-AMPK as potential therapeutic targets for cancer prevention and intervention.

Public Health Relevance

Cancer is a devastating disease in which better understanding of its biology and finding a good therapeutic strategy are critically needed. Our research goals seek to identify the mechanism by which breast cancer and liver cancer develop and to find a solution for the treatment of this disease. Our study will not only reveal novel insights into how breast and liver cancer progression is regulated, but also offer novel paradigms and targets for breast and liver cancer prevention and intervention.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
1R01CA182424-01A1
Application #
8759951
Study Section
Molecular Oncogenesis Study Section (MONC)
Program Officer
Hildesheim, Jeffrey
Project Start
2014-08-01
Project End
2019-07-31
Budget Start
2014-08-01
Budget End
2015-07-31
Support Year
1
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Texas MD Anderson Cancer Center
Department
Microbiology/Immun/Virology
Type
Hospitals
DUNS #
City
Houston
State
TX
Country
United States
Zip Code
77030
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