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Published on: July 17, 2020
Hyperphosphorylated PTEN exerts oncogenic properties
Janine H van Ree1, Karthik B Jeganathan1, Raul O Fierro Velasco1
1Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN, USA.
Abstract:
PTEN is a multifaceted tumor suppressor that is highly sensitive to alterations in expression or function. The PTEN C-tail domain, which is rich in phosphorylation sites, has been implicated in PTEN stability, localization, catalytic activity, and protein interactions, but its role in tumorigenesis remains unclear. To address this, we utilized several mouse strains with nonlethal C-tail mutations. Mice homozygous for a deletion that includes S370, S380, T382 and T383 contain low PTEN levels and hyperactive AKT but are not tumor prone. Analysis of mice containing nonphosphorylatable or phosphomimetic versions of S380, a residue hyperphosphorylated in human gastric cancers, reveal that PTEN stability and ability to inhibit PI3K-AKT depends on dynamic phosphorylation-dephosphorylation of this residue. While phosphomimetic S380 drives neoplastic growth in prostate by promoting nuclear accumulation of β-catenin, nonphosphorylatable S380 is not tumorigenic. These data suggest that C-tail hyperphosphorylation creates oncogenic PTEN and is a potential target for anti-cancer therapy.
Insights
Altered PTEN C-tail phosphorylation can create oncogenic PTEN, driving cancer growth. Targeting this C-tail hyperphosphorylation offers a potential anti-cancer therapy strategy.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- PTEN is a critical tumor suppressor sensitive to expression and functional changes.
- The PTEN C-tail domain's role in tumorigenesis is unclear despite its involvement in PTEN stability, localization, activity, and interactions.
Purpose of the Study:
- To investigate the role of PTEN C-tail phosphorylation in tumorigenesis.
- To determine how specific phosphorylation events on the PTEN C-tail influence its tumor-suppressive functions.
Main Methods:
- Utilized mouse models with specific C-tail mutations (deletions, nonphosphorylatable, and phosphomimetic variants).
- Analyzed PTEN levels, AKT activity, and tumorigenic potential in these mouse strains.
- Examined the impact of S380 phosphorylation dynamics on PTEN stability and PI3K-AKT inhibition.
Main Results:
- Deletion of C-tail sites (S370, S380, T382, T383) led to low PTEN and hyperactive AKT but did not promote tumors.
- Phosphorylation dynamics at S380 are crucial for PTEN stability and PI3K-AKT pathway inhibition.
- A phosphomimetic S380 variant promoted prostate cancer growth via nuclear beta-catenin accumulation, while a nonphosphorylatable S380 variant was not tumorigenic.
Conclusions:
- PTEN C-tail hyperphosphorylation can paradoxically create an oncogenic form of PTEN.
- Dynamic phosphorylation of the PTEN C-tail, particularly at S380, is essential for its tumor suppressor activity.
- PTEN C-tail hyperphosphorylation represents a potential therapeutic target for cancer treatment.
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