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Distinct roles of AKT isoforms in regulating β1-integrin activity, migration, and invasion in prostate cancer
Reetta Virtakoivu1, Teijo Pellinen, Juha K Rantala
1VTT Medical Biotechnology, Turku FIN-20520, Finland.
Abstract:
AKT1 and AKT2 kinases have been shown to play opposite roles in breast cancer migration and invasion. In this study, an RNA interference screen for integrin activity inhibitors identified AKT1 as an inhibitor of β1-integrin activity in prostate cancer. Validation experiments investigating all three AKT isoforms demonstrated that, unlike in breast cancer, both AKT1 and AKT2 function as negative regulators of cell migration and invasion in PC3 prostate cancer cells. Down-regulation of AKT1 and AKT2, but not AKT3, induced activation of cell surface β1-integrins and enhanced adhesion, migration, and invasion. Silencing of AKT1 and AKT2 also resulted in increased focal adhesion size. Importantly, the mechanisms involved in integrin activity regulation were distinct for the two AKT isoforms. Silencing of AKT1 relieved feedback suppression of the expression and activity of several receptor tyrosine kinases, including EGFR and MET, with established cross-talk with β1-integrins. Silencing of AKT2, on the other hand, induced up-regulation of the microRNA-200 (miR-200) family, and overexpression of miR-200 was sufficient to induce integrin activity and cell migration in PC3 cells. Taken together, these data define an inhibitory role for both AKT1 and AKT2 in prostate cancer migration and invasion and highlight the cell type-specific actions of AKT kinases in the regulation of cell motility.
Insights
In prostate cancer cells, AKT1 and AKT2 kinases inhibit migration and invasion. Silencing these AKT kinases activates integrins, promoting cell movement and invasion through distinct molecular pathways.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- AKT1 and AKT2 kinases exhibit opposing roles in breast cancer cell migration and invasion.
- Integrin activity is crucial for cell adhesion, migration, and invasion in various cancers.
Purpose of the Study:
- To investigate the role of AKT isoforms (AKT1, AKT2, AKT3) in regulating cell migration and invasion in prostate cancer.
- To elucidate the molecular mechanisms by which AKT kinases influence integrin activity and cell motility in prostate cancer.
Main Methods:
- RNA interference (RNAi) screen to identify inhibitors of integrin activity.
- Validation experiments using gene silencing of AKT isoforms in PC3 prostate cancer cells.
- Analysis of cell surface β1-integrin activation, cell adhesion, migration, invasion, and focal adhesion size.
- Investigation of downstream signaling pathways, including receptor tyrosine kinases (EGFR, MET) and microRNA-200 (miR-200) family.
Main Results:
- Unlike in breast cancer, both AKT1 and AKT2 act as negative regulators of migration and invasion in PC3 prostate cancer cells.
- Down-regulation of AKT1 and AKT2, but not AKT3, led to β1-integrin activation, enhanced cell adhesion, migration, and invasion, and increased focal adhesion size.
- Silencing AKT1 reduced feedback suppression of receptor tyrosine kinases (EGFR, MET), while silencing AKT2 induced up-regulation of the miR-200 family, which was sufficient to promote integrin activity and migration.
Conclusions:
- Both AKT1 and AKT2 play inhibitory roles in prostate cancer cell migration and invasion.
- The mechanisms by which AKT1 and AKT2 regulate integrin activity are distinct and cell type-specific.
- These findings highlight the complex and context-dependent functions of AKT kinases in cancer cell motility.
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