title: PP2A inhibitors arrest G2/M transition through JNK/Sp1- dependent down-regulation of CDK1 and autophagy-dependent up-regulation of p21.
abstract: Protein phosphatase 2A (PP2A) plays an important role in the control of the cell cycle. We previously reported that the PP2A inhibitors, cantharidin and okadaic acid (OA), efficiently repressed the growth of cancer cells. In the present study, we found that PP2A inhibitors arrested the cell cycle at the G2 phase through a mechanism that was dependent on the JNK pathway. Microarrays further showed that PP2A inhibitors induced expression changes in multiple genes that participate in cell cycle transition. To verify whether these expression changes were executed in a PP2A-dependent manner, we targeted the PP2A catalytic subunit (PP2Ac) using siRNA and evaluated gene expression with a microarray. After the cross comparison of these microarray data, we identified that CDK1 was potentially the same target when treated with either PP2A inhibitors or PP2Ac siRNA. In addition, we found that the down-regulation of CDK1 occurred in a JNK-dependent manner. Luciferase reporter gene assays demonstrated that repression of the transcription of CDK1 was executed through the JNK-dependent activation of the Sp1 transcription factor. By constructing deletion mutants of the CDK1 promoter and by using ChIP assays, we identified an element in the CDK1 promoter that responded to the JNK/Sp1 pathway after stimulation with PP2A inhibitors. Cantharidin and OA also up-regulated the expression of p21, an inhibitor of CDK1, via autophagy rather than PP2A/JNK pathway. Thus, this present study found that the PP2A/JNK/Sp1/CDK1 pathway and the autophagy/p21 pathway participated in G2/M cell cycle arrest triggered by PP2A inhibitors.
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.|Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, China.|Jiangsu Institute of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, China.|Key Laboratory of Thrombosis and Hemostasis of Ministry of Health, The First Affiliated Hospital of Soochow University, Suzhou, China.|Collaborative Innovation Center of Hematology, Soochow University, Suzhou, China.
authors.forename: Fei-Ran
authors.initials: FR
authors.lastname: Gong
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Meng-Yao
authors.initials: MY
authors.lastname: Wu
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Shen
authors.affiliation: Department of General Surgery, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Qiaoming
authors.initials: Q
authors.lastname: Zhi
authors.affiliation: Department of General Surgery, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Ze-Kuan
authors.initials: ZK
authors.lastname: Xu
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Wen-Jie
authors.initials: WJ
authors.lastname: Wang
authors.affiliation: Department of General Surgery, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.|Department of General Surgery, The Changshu No.1 People's Hospital, Changshu, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zong
authors.affiliation: Department of General Surgery, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Zeng-Liang
authors.initials: ZL
authors.lastname: Li
authors.affiliation: Departments of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, KY, USA.|Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY, USA.
authors.forename: Yadi
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Departments of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA.|Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY, USA.
authors.forename: Binhua P
authors.initials: BP
authors.lastname: Zhou
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Chen
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.|Jiangsu Institute of Clinical Immunology, Suzhou, China.|Institute of Medical Biotechnology, Soochow University, Suzhou, China.|PREMED Key Laboratory for Precision Medicine, Soochow University, Suzhou, China.
authors.forename: Min
authors.initials: M
authors.lastname: Tao
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China.|PREMED Key Laboratory for Precision Medicine, Soochow University, Suzhou, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
mesh_terms: D001343:Autophagy / Q000187:drug effects / Q000235:genetics*; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D002193:Cantharidin / Q000494:pharmacology; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D061986:MCF-7 Cells; D019319:Okadaic Acid / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D016329:Sp1 Transcription Factor; D019319:Okadaic Acid; D016203:CDC2 Protein Kinase; D048031:JNK Mitogen-Activated Protein Kinases; D054648:Protein Phosphatase 2; D002193:Cantharidin
keywords: CDK1; G2/M cell cycle arrest; JNK; PP2A; Sp1