PT  - JOURNAL ARTICLE
AU  - Yoshito Hayashi
AU  - Masahiko Tsujii
AU  - Jun Wang
AU  - Jumpei Kondo
AU  - Tomofumi Akasaka
AU  - Ying Jin
AU  - Wei Li
AU  - Toru Nakamura
AU  - Tsutomu Nishida
AU  - Hideki Iijima
AU  - Shingo Tsuji
AU  - Sunao Kawano
AU  - Norio Hayashi
AU  - Tetsuo Takehara
TI  - CagA mediates epigenetic regulation to attenuate let-7 expression in <em>Helicobacter pylori</em>-related carcinogenesis
AID  - 10.1136/gutjnl-2011-301625
DP  - 2013 Nov 01
TA  - Gut
PG  - 1536--1546
VI  - 62
IP  - 11
4099  - http://gut.bmj.com/content/62/11/1536.short
4100  - http://gut.bmj.com/content/62/11/1536.full
SO  - Gut2013 Nov 01; 62
AB  - Objective MicroRNAs (miRNAs) act as tumour suppressor genes or oncogenes in the regulation of multiple carcinogenic processes. Aberrant miRNA expression is reported in Helicobacter pylori (H pylori)-related gastritis and gastric cancer. The cytotoxin-associated gene A (CagA) of H pylori has a pathophysiologically important role in gastric carcinogenesis. A study was undertaken to evaluate the effect of CagA on miRNA expression and its regulatory mechanism. Methods The effect of CagA on miRNA expression was assessed by comprehensive miRNA microarray. The mechanisms of the in vitro and in vivo effects of CagA on histone modification and DNA methylation and the involvement of CagA-dysregulated signal transduction on let-7, an important representative miRNA in gastric carcinogenesis, were investigated. Results In in vitro experiments, CagA significantly attenuated let-7 expression leading to Ras pathway activation. CagA enhanced c-myc, DNA methyltransferase 3B (DNMT3B) and Enhancer of Zeste homologue 2 (EZH2) expression and attenuated miR-26a and miR-101 expression, which resulted in the attenuation of let-7 expression by histone and DNA methylation. Experiments performed in CagA transgenic mice revealed that c-myc, EZH2 and DNMT3B expression were enhanced and let-7 expression was attenuated to induce Ras oncoprotein expression in the stomach, with no associated inflammation. Conclusions H pylori CagA induces aberrant epigenetic silencing of let-7 expression, leading to Ras upregulation.