title: NF-κB targets miR-16 and miR-21 in gastric cancer: involvement of prostaglandin E receptors.
abstract: Cigarette smoke is one of the risk factors for gastric cancer and nicotine has been reported to promote tumor growth. Deregulation of microRNA (miRNA) and cyclooxygenase-2 (COX-2) expressions are hallmarks of many cancers including gastric cancer. Here, we used an miRNA array platform covering a panel of 95 human miRNAs to examine the expression profile in nicotine-treated gastric cancer cells. We found that miR-16 and miR-21 were upregulated upon nicotine stimulation, transfection with anti-miR-16 or anti-miR-21 significantly abrogated cell proliferation. In contrast, ectopic miR-16 or miR-21 expression exhibited a similar stimulatory effect on cell proliferation as nicotine. Nicotine-mediated IkappaBα degradation and nuclear factor-kappa B (NF-κB) translocation dose-dependently. Knockdown of NF-κB by short interfering RNA (siRNA) or specific inhibitor (Bay-11-7085) markedly suppressed nicotine-induced cell proliferation and upregulation of miR-16 and miR-21. Interestingly, NF-κB-binding sites were located in both miR-16 and miR-21 gene transcriptional elements and we showed that nicotine enhanced the binding of NF-κB to the promoters of miR-16 and miR-21. Furthermore, activation of COX-2/prostaglandin E₂ (PGE₂) signaling in response to nicotine was mediated by the action of prostaglandin E receptors (EP2 and EP4). EP2 or EP4 siRNA or antagonists impaired the nicotine-mediated NF-κB activity, upregulation of miR-16 and miR-21 and cell proliferation. Taken together, these results suggest that miR-16 and miR-21 are directly regulated by the transcription factor NF-κB and yet nicotine-promoted cell proliferation is mediated via EP2/4 receptors. Perhaps this study may shed light on the development of anticancer drugs to improve the chemosensitivity in smokers.
authors.affiliation: Department of Surgery, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong SAR, China. vyshin@hku.hk
authors.forename: Vivian Y
authors.initials: VY
authors.lastname: Shin
authors.forename: Hongchuan
authors.initials: H
authors.lastname: Jin
authors.forename: Enders K O
authors.initials: EK
authors.lastname: Ng
authors.forename: Alfred S L
authors.initials: AS
authors.lastname: Cheng
authors.forename: Wilson W S
authors.initials: WW
authors.lastname: Chong
authors.forename: Christine Y P
authors.initials: CY
authors.lastname: Wong
authors.forename: Wai K
authors.initials: WK
authors.lastname: Leung
authors.forename: Joseph J Y
authors.initials: JJ
authors.lastname: Sung
authors.forename: Kent-Man
authors.initials: KM
authors.lastname: Chu
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D035683:MicroRNAs / Q000502:physiology*; D016328:NF-kappa B / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology; D058307:Receptors, Prostaglandin E, EP2 Subtype / Q000502:physiology*; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000502:physiology*; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000473:pathology*
chemical_list: C505362:MIRN16 microRNA, human; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; C545644:PTGER2 protein, human; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D009538:Nicotine