The p53 gene has been referred to as 'the guardian of the genome' because it 
controls apoptosis and cell cycle arrest. The purpose of this study was to 
evaluate the association of p53 codon 72 genetic polymorphism and the p53 
immunohistochemistry with Helicobacter pylori-associated gastroduodenal 
diseases, including gastric cancer. This study included 1,852 subjects: controls 
and patients with gastric cancer, dysplasia, benign gastric ulcers, and duodenal 
ulcers (DU). Biallelic polymorphism was genotyped by restriction fragment length 
polymorphism. Immunohistochemical analysis for the detection of mutant type p53 
expression was performed. The frequency of the Pro/Pro allele of the p53 codon 
72 was higher in the patients with H. pylori-positive dysplasia than in controls 
(OR: 2.3, 95% CI: 1.3-4.3), but it was less frequent among patients with a H. 
pylori-positive DU (OR: 0.5, 95% CI: 0.3-0.8). However, there was no significant 
association with gastric cancer, including the location, stage, or histological 
type of gastric cancer. Expression of a mutant type of p53 protein was detected 
in 6.3% of dysplastic tissues and 26.5% of cancerous tissues compared 0% in the 
controls. Positive expression was higher in the intestinal type of cancer 
(34.9%) than in the diffuse type (15.0%; P = 0.001). These results suggest that 
genetic polymorphism of p53 codon 72 played a role in the determination of H. 
pylori-associated gastroduodenal diseases, but p53 immunostaining did not 
correlate with those of the p53 genetic polymorphism analysis.