Claudin-18 knockdown by siRNA. (A) Claudin-18 siRNA significantly decreases the mRNA level of claudin-18 in MKN74.

<p>(B) Staining of claudin-18 is reduced by claudin-18 siRNA treatment. Bar = 50 µm. Each value represents the mean ± SD of 3 independent experiments. **<i>P</i><0.01 vs. control or control siRNA.</p

HE staining and immunofluorescence staining of claudin-18 in gastric cancer (GC) lesions and surrounding gastric mucosa.

<p>(A) HE staining of gastric mucosa with non-intestinal metaplasia (non-IM), intestinal metaplasia (IM), and cancer. Claudin-18 is detected in gastric mucosa with non-IM at the surface border and lateral membrane of the epithelial cells, but not with IM or cancer. White bar = 100 µm, Yellow bar = 50 µm. (B) Claudin-18 level is significantly lower in GC than in non-IM or IM. The level is also significantly lower in IM than in non-IM. ^#<i>P</i><0.05 vs. IM. **<i>P</i><0.01 vs. non-IM.</p

Clinicopathological features of gastric cancer patients.

<p>T1a; tumor confined to the mucosa, T1b; tumor confined to the submucosa,</p><p>U; upper third, M; middle third, L; lower third <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074757#pone.0074757-JapaneseGastricCancerAssocciation1" target="_blank">[18]</a></p

Effect of claudin-18 knockdown on the proliferation and invasion of GC cells.

<p>(A) Claudin-18 siRNA treatment significantly induces cell proliferation. (B) Claudin-18 siRNA-transfected MKN74 cells show a significantly higher invasion ratio compared to control or control siRNA-transfected cells. Typical images are presented at the top. Bar = 500 µm. Each value represents the mean ± SD of 3 independent experiments. **<i>P</i><0.01 vs. control or control siRNA.</p

IL-33 expression in esophageal epithelial layers of patients with heartburn and controls.

<p>IL-33 mRNA expression was analyzed using qRT-PCR and was compared at the middle (A) and distal (B) esophagus of control samples, and the heartburn patients (Total), the subjects who were not taking a PPI (no PPI) and who were (PPI). (C) Representative immunofluorescence staining of IL-33 in the apical and basal layers of the distal esophagus of a control sample and a heartburn patient with taking a PPI is shown. DAPI was used for nuclear staining. *<i>P</i> < 0.05, **<i>P</i> < 0.01, ***<i>P</i> < 0.001, ^<b>▲</b><i>P</i> = 0.08 vs. Control; ns, not significant vs. no PPI. Bar = 100 μm.</p

Relative levels of cytokine mRNAs.

<p>Relative levels of cytokine mRNAs.</p

Histological characteristics in patients and controls.

<p>Histological characteristics in patients and controls.</p

Intercellular space (ICS) diameters of the esophagus in patients with heartburn patients and controls.

<p>Middle and distal esophageal biopsy specimens were stained with hematoxylin and eosin. Intercellular space diameters of the middle (A) and distal (B) esophagus at the basal layers of squamous epithelial cells were then measured in control samples and heartburn patients (Total). The heartburn patients (Total) consist of the subjects who were not taking a PPI (no PPI) and who were (PPI). The horizontal line in each sample indicates the median value. *<i>P</i> < 0.05, **<i>P</i> < 0.01, ***<i>P</i> < 0.001 vs. Control; ns, not significant vs. no PPI.</p