title: TIPE2, a negative regulator of TLR signaling, regulates p27 through IRF4-induced signaling.
abstract: Targeted inhibition of specific toll-like receptor (TLR) pathways may provide an effective strategy to prevent the development of selected gastric malignancies. Tumor necrosis factor (TNF)-α-induced protein 8-like-2 (TIPE2) was identified as a novel negative regulator of TLR signaling. Our previous study identified TIPE2 as an inhibitor of gastric cancer cell growth; it promotes p27 expression, which leads to restored control of the cell cycle and cell division. However, the molecular mechanism by which TIPE2 regulates p27 remains unclear. In the present study, we examined the expression patterns of TIPE2 in serial clinical gastritis tissues as well as gastric cancer, and found a negative correlation between TIPE2 expression and progression of gastritis to gastric cancer. This negative correlation verified the role of TIPE2 in preventing the occurrence and development of gastric cancer, suggesting that TIPE2 may be a potential biomarker for gastric cancer progression. To determine the mechanism employed by TIPE2 in gastric cell carcinogenesis, a TIPE2-expressing plasmid was introduced into gastric cell lines, and microarray and western blot analysis revealed that TIPE2 selectively upregulates the expression of interferon regulatory factor 4 (IRF4). Variations in IRF4 expression were additionally verified in knockout mice. Next, the effect of IRF4 on p27 expression was tested by an IRF4 siRNA interference assay. Finally, we explored the signaling pathways used by TIPE2 to regulate IRF4. An experiment using pathway inhibitors and a nuclear factor κ-light-chain enhancer of activated B cells (NF-κB) luciferase reporter assay showed that NF-κB plays a crucial role in regulating IRF4 expression. Our data provide evidence that TIPE2, a potential biomarker for gastric cancer progression, stimulates an IRF4-associated signaling cascade that promotes p27 expression and controls cell growth. To the best of our knowledge, this is the first study to demonstrate that IRF4 acts as an inhibitor of epithelial cell proliferation and mediates the expression of TIPE2, a negative regulator of TLR signaling, to control cell growth.
authors.affiliation: School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Peng
authors.affiliation: School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China.
authors.forename: Hanyu
authors.initials: H
authors.lastname: Zhang
authors.affiliation: School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China.
authors.forename: Bo
authors.initials: B
authors.lastname: Han
authors.affiliation: School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China.
authors.forename: Suxia
authors.initials: S
authors.lastname: Liu
authors.affiliation: School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China.
authors.forename: Mingyong
authors.initials: M
authors.lastname: Han
authors.affiliation: School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China.
authors.forename: Shili
authors.initials: S
authors.lastname: Liu
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D050835:Interferon Regulatory Factors / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D009368:Neoplasm Transplantation; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051193:Toll-Like Receptors / Q000378:metabolism; D000099218:Interferon Regulatory Factor-4
chemical_list: D050760:Cyclin-Dependent Kinase Inhibitor p27; D050835:Interferon Regulatory Factors; D047908:Intracellular Signaling Peptides and Proteins; D051193:Toll-Like Receptors; D000099218:Interferon Regulatory Factor-4; C436291:CDKN1B protein, human; C552057:TNFAIP8L2 protein, human