Notch-1 signaling activates NF-jB in human breast carcinoma MDA-MB-231 cells via PP2A-dependent AKT pathway Li Li 1 • Jing Zhang 1 • Niya Xiong 1 • Shun Li 1 • Yu Chen 1 • Hong Yang 1,2 • Chunhui Wu 1,2 • Hongjuan Zeng 1,2 • Yiyao Liu 1,2 Received: 15 January 2016 / Accepted: 22 February 2016 Ó Springer Science+Business Media New York 2016 Abstract 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-jB 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-jB activation is still poorly under- stood. Here, we aim to understand the exact mechanism that Notch-1 regulates NF-jB activity. In MDA-MB-231 cells where Notch-1 is constitutively activated, the phosphoryla- tion of p85 and AKT (Tyr308/Ser473) is upregulated, indi- cating PI3K/AKT pathway is activated. Notch-1 activation caused the increase of PP2A phosphorylation at Tyr307, indicating Notch-1 inhibits PP2A activity. NF-jB tran- scriptional activity was evaluated by dual-luciferase reporter assay, and the results showed that, while silencing of Notch- 1, PP2A activity was upregulated and NF-jB activity was downregulated, whereas PP2A inhibitor okadaic acid (OA) restored NF-jB 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-jB pathway is PP2A dependent; PP2A may be a potential therapeutic target in breast cancer. Keywords Notch-1 Á NF-jB Á PP2A Á Invasion Á PI3K/AKT Introduction Breast cancer is the most common malignant cancer and the leading cause of cancer death among women in the world [1, 2]. Although advances in detection and treatment have increased breast cancer survival rate, tumor metastasis reduces the survival rate dramatically. Therefore, finding targets to treat or prevent tumor metastasis is an important therapeutic priority [3]. Mutations in human breast cancer have been identified as activating expression or elevating the function of oncogenes, and disrupting tumor suppressor genes [4]. Notch is highly conserved and crucial for cell death, proliferation, differentiation and development. Notch sig- naling pathway is initiated by interactions between Notch receptors and their ligands. In mammals, there are four Notch receptors (Notch-1–Notch-4). Notch undergoes posttranslational processing before it is fully functional. It is activated through binding of appropriate ligands (Jag- ged-1–Jagged-2 and Delta 1–Delta-3) on neighboring cells, leading to the cleavage and releasing of Notch intracellular domain (NICD). NICD translocates into nucleus initiating the expression of Notch target genes, e.g., HES and HERP/ HEY family genes. Notch signaling participates in neo- plastic transformation in various cell types, such as cervical cancer [5], lung cancer [6] and a variety of breast cancers & Yiyao Liu liuyiyao@uestc.edu.cn 1 Department of Biophysics, School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan, People’s Republic of China 2 Center for Information in Biomedicine, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan, People’s Republic of China 123 Med Oncol (2016)33:33 DOI 10.1007/s12032-016-0747-7