1. Nanog expression is negatively regulated by protein kinase C activities in human cancer cell lines.
- Author
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Chu WK, Dai PM, Li HL, Pao CC, and Chen JK
- Subjects
- Carcinoma, Cell Proliferation, Disease Progression, Dose-Response Relationship, Drug, Enzyme Activation, Enzyme Inhibitors pharmacology, Gene Silencing, Hep G2 Cells, Homeodomain Proteins genetics, Humans, Isoenzymes genetics, Isoenzymes metabolism, Mutagenesis, Site-Directed, Nanog Homeobox Protein, Nasopharyngeal Carcinoma, Nasopharyngeal Neoplasms enzymology, Nasopharyngeal Neoplasms pathology, Octamer Transcription Factor-3 genetics, Octamer Transcription Factor-3 metabolism, Promoter Regions, Genetic, Protein Kinase C-alpha antagonists & inhibitors, Protein Kinase C-alpha genetics, Protein Kinase C-delta antagonists & inhibitors, Protein Kinase C-delta genetics, RNA, Messenger genetics, RNA, Messenger metabolism, SOXB1 Transcription Factors genetics, SOXB1 Transcription Factors metabolism, Tetradecanoylphorbol Acetate analogs & derivatives, Tetradecanoylphorbol Acetate pharmacology, Transcription, Genetic, Gene Expression Regulation, Neoplastic, Homeodomain Proteins metabolism, Protein Kinase C-alpha metabolism, Protein Kinase C-delta metabolism
- Abstract
Nanog is a transcription factor that is essential for the maintenance of pluripotency of the embryonic stem cells. Nanog has been shown to be expressed in various kinds of human tumors, suggesting a role in tumorigenesis. In this study, we found that Nanog expression was upregulated by inhibition of protein kinase C (PKC) activity in six human cancer cell lines examined. In a Nanog non-expressing human nasopharyngeal carcinoma cell line, NPC-076, Nanog mRNA level and protein level were both induced and dose-dependently promoted by exposure to PKC inhibitors. Knockdown experiments showed that PKCα and PKCδ were two subtypes exerted most of the effect. The reporter assay showed that Nanog promoter activity was promoted by exposure of the cells to PKC inhibitors and the effect was dependent on the presence of the Octamer-Sox composite element. The involvement of Octamer-Sox composite element was further supported by the observation that silencing of Oct4 and Sox2 in NPC-076 cells attenuated the effects of PKC inhibitors. In Nanog-expressing human embryonal carcinoma cell lines, NT2/D1 and NCCIT, Nanog expression was suppressed by exposure to PKC activator Phorbol-12-myristate-13-acetate (PMA). Further study showed that overexpression of PKCα elicited a repressive effect on Nanog expression in NT2/D1 cells. Consistently, mutation of the Octamer-Sox composite element abolished the suppressive effect by PKC activator. Nanog expression was of cellular significance in that ectopic expression in NPC-076 stimulated cell proliferation and knockdown of the endogenous Nanog expression in NT2/D1-suppressed cell proliferation.
- Published
- 2013
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