**3. 8-Nitroguanine accumulation in inflammation-related cancer**

### **3.1 Application of Immunochemistry employing anti-8-nitroguanine antibody**

We have performed immunohistochemical analysis for 8-nitroguanine formation in various clinical specimens and animal models of inflammation-related carcinogenesis. We have firstly demonstrated that 8-nitroguanine is formed at the sites of carcinogenesis regardless of etiology, and we have proposed the possibility that 8-nitroguanine is a potential biomarker to evaluate the risk of inflammation-associated carcinogenesis (Kawanishi & Hiraku, 2006; Kawanishi et al., 2006). In clinical specimens, 8-nitroguanine was formed in the gastric grand epithelial cells of patients with gastritis caused by *Helicobacter pylori* (*H. pylori*)

8-Nitroguanine, a Potential Biomarker to

Evaluate the Risk of Inflammation-Related Carcinogenesis 209

4A, B). Despite the complete eradication of *H. pylori*, reduced 8-nitroguanine and 8-oxodG production by infiltrating inflammatory cells were found only in 26% and 36% patients, respectively. Mean 8-nitroguanine and 8-oxodG immunoreactivities in inflammatory cells

Fig. 3. 8-Nitroguanine and 8-oxodG formation in gastritis patients with and without *H. pylori* infection. Double immunofluorescence staining of paraffin sections shows the localization of 8-oxodG and 8-nitroguanine in the gastric epithelium. In *H. pylori*-infected patients (HP(+)), the immunoreactivity of 8-nitroguanine and 8-oxodG co-localizes

corpus (Merged). In chronic gastritis patients without *H. pylori*-infection (HP(-)), the immunoreactivity of 8-nitroguanine and 8-oxodG is observed mainly in the inflammatory cells, while the gastric gland epithelial cells displayed little or no immunoreactivity. Scale

bar represents 50 m.

primarily in the nuclei of gastric gland epithelial cells and in some inflammatory cells in the

was not significantly decreased after the eradication treatment.

infection (Ma et al., 2004), hepatocytes of patients with chronic hepatitis C (Horiike et al., 2005), oral precancerous lesions oral lichen planus (OLP) (Chaiyarit et al., 2005) and oral leukoplakia (Ma et al., 2006), soft tissue sarcoma (Hoki et al., 2007a; Hoki et al., 2007b) and Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) (Ma et al., 2008).

In animal models, 8-nitroguanine was formed in a mouse model of inflammatory bowel disease (IBD) (Ding et al., 2005). 8-Nitroguanine was formed in the bile duct epithelium of the liver of hamsters infected with the liver fluke, *Opisthorchis viverrini*, which causes cancer of intrahepatic bile duct (Pinlaor et al., 2003; Pinlaor et al., 2004a). The treatment with praziquantel, an antiparasitic drug, reduced 8-nitroguanine formation (Pinlaor et al., 2006).
