한빛사 논문
Abstract
Received 5 February 2008; accepted 18 August 2008. published online 22 August 2008.
Background & AimsHuR is a RNA-binding factor whose expression is commonly upregulated in some human tumor types. We explored the molecular mechanism underlying HuR elevation and its role in gastric cancer tumorigenesis.
MethodsHuR expression and subcellular localization were determined by polymerase chain reaction, immunoblot, and immunohistochemical analyses. Its effect on tumor growth was characterized using flow cytometry, terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling, and soft agar analyses. Luciferase reporter, chromatin immunoprecipitation, and electrophoretic mobility shift assays were used to measure transcriptional activation by nuclear factor κB (NF-κB) signaling.
ResultsCompared with normal gastric tissues, HuR was expressed at higher levels in gastric tumors, particularly in advanced versus early tumors; this increase was associated with enhanced cytoplasmic translocation of HuR. HuR overexpression increased proliferation of tumor cells, activating the G1 to S transition of the cell cycle, DNA synthesis, and anchorage-independent growth. Small interfering RNA–mediated knockdown of HuR expression reduced tumor cell proliferation and response to apoptotic stimuli. No genetic or epigenetic alterations of HuR were observed in gastric tumor cell lines or primary tumors; overexpression depended on phosphatidylinositol 3-kinase/AKT signaling and NF-κB activity. AKT activation increased p65/RelA binding to a putative NF-κB binding site in the HuR promoter, the stability of HuR target transcripts, and the cytoplasmic import of HuR.
ConclusionsHuR is a direct transcription target of NF-κB; its activation in gastric cancer cell lines depends on phosphatidylinositol 3-kinase/AKT signaling. HuR activation by this pathway has proliferative and antiapoptotic effects on gastric cancer cells.
Abbreviations used in this paper: ARE, adenylate uridylate–rich elements, FBS, fetal bovine serum, 5-FU, 5-fluorouracil, IGF, insulin-like growth factor, NF-κB, nuclear factor-κB, PI3K, phosphatidylinositol 3-kinase, PCR, polymerase chain reaction, RT, reverse transcription, siRNA, short interfering RNA
* School of Life Sciences and Biotechnology, Korea University, Seoul, Korea
‡ Department of Biology Education, Teacher''s College, Kyungpook National University, Daegu, Korea
§ Food Safety Research Division, Korea Food Research Institute, Kyonggi-do, Korea
∥ Department of General Surgery, School of Medicine, Kyung Hee University, Seoul, Korea
¶ Department of Internal Medicine, School of Medicine, Kyung Hee University, Seoul, Korea
**Address requests for reprints to: Sung–Gil Chi, PhD, School of Life Sciences and Biotechnology, Korea University, 136-701 Seoul, Republic of Korea. fax: (82) 2-927-5458
The authors disclose the following: Supported in part by grants from the Korea Science and Engineering Foundation (R01-2006-000-10688-0 and Biofood R&D R053123), the Korea Research Foundation (2003-070-C00031), and the National Cancer Center, Korea (0420230), Republic of Korea.
PII: S0016-5085(08)01518-7
doi:10.1053/j.gastro.2008.08.009
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