Notch-1 signaling activates NF-κB in human breast carcinoma MDA-MB-231 cells via PP2A-dependent AKT pathway
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Breast cancer has a high incidence in the world and is becoming a leading cause of death in female patients due to its high metastatic ability. High expression of Notch-1 and its ligand Jagged-1 correlates with poor prognosis in breast cancer. Our previous work has shown that Notch-1 signaling pathway upregulates NF-κB transcriptional activity and induces the adhesion, migration and invasion of human breast cancer cell line MDA-MB-231. However, the role of Notch-1 in NF-κB activation is still poorly understood. Here, we aim to understand the exact mechanism that Notch-1 regulates NF-κB activity. In MDA-MB-231 cells where Notch-1 is constitutively activated, the phosphorylation of p85 and AKT (Tyr308/Ser473) is upregulated, indicating PI3K/AKT pathway is activated. Notch-1 activation caused the increase of PP2A phosphorylation at Tyr307, indicating Notch-1 inhibits PP2A activity. NF-κB transcriptional activity was evaluated by dual-luciferase reporter assay, and the results showed that, while silencing of Notch-1, PP2A activity was upregulated and NF-κB activity was downregulated, whereas PP2A inhibitor okadaic acid (OA) restored NF-κB activity. Immunofluorescence and Western blots showed that OA treatment antagonized the decrease of p65 nuclear translocation caused by Notch-1 silencing. Moreover, OA treatment also upregulated MMP-2, MMP-9 and VEGF mRNA expression levels, indicating OA rescues Notch-1 silencing that caused low cell invasion. Taken together, our results suggest that Notch-1-activating PI3K/AKT/NF-κB pathway is PP2A dependent; PP2A may be a potential therapeutic target in breast cancer.
KeywordsNotch-1 NF-κB PP2A Invasion PI3K/AKT
We thank Dr. Ping Tang and Dr. Chao Feng for the assistance with the manuscript and valuable advice and Juan Lu who provided experimental assistance. This work was supported, in whole or in part, by the National Natural Science Foundation of China (11272083, 81201192, 81101147, 31470906, 31470959, 81471785, and 11502049) and the Sichuan Youth Science and Technology Foundation of China (2014JQ0008, 2010JQ0004).
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Conflict of interest
The authors declare that they have no conflict of interest.
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