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.
Digital Object Identifier (DOI)
This work was supported by grants from the National Natural Science Foundation of China [Nos. 81472296, 81101867, 81072031, 81272542, 81200369, and 81402477]; the CSPAC-Celgene Foundation; the Natural Science Foundation of Jiangsu Province [No. BK2010585]; China International Medical Foundation [No. CIMF-F-H001-057]; the Medical Scientific Research Project of Jiangsu Provincial Bureau of Health (Z201206); the Special Foundation of Wu Jieping Medical Foundation for Clinical Scientific Research [Nos. 320.6753.1225 and 320.6750.12242]; the Science and Education for Health Foundation of Suzhou for Youth [Nos. SWKQ1003 and SWKQ1011]; the Science and Technology Project Foundation of Suzhou [Nos. SYS201112 and SYSD2012137]; the Science and Technology Foundation of Suzhou Xiangcheng (Nos. SZXC2012-70 and XJ201451); a Project Founded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
Gong, Fei-Ran; Wu, Meng-Yao; Shen, Meng; Zhi, Qiaoming; Xu, Ze-Kuan; Wang, Rong; Wang, Wen-Jie; Zong, Yang; Li, Zeng-Liang; Wu, Yadi; Zhou, Binhua P.; Chen, Kai; Tao, Min; and Li, Wei, "PP2A Inhibitors Arrest G2/M Transition Through JNK/Sp1-Dependent Down-Regulation of CDK1 and Autophagy-Dependent Up-Regulation of p21" (2015). Markey Cancer Center Faculty Publications. 51.