| Popis: |
It is now widely accepted that reactive oxygen species (ROS), generated as a consequence of chronic inflammation, can be both mutagenic and carcinogenic and are believed to play an important role in the initiation of gastric carcinogenesis. In this study the Electron Spin Resonance (ESR) spectroscopy technique and Restriction Site Mutation (RSM) assay were used to investigate the role of ROS in gastric cancer. ESR was employed to directly measure the levels of free radicals in precancerous and cancerous gastric tissue. My findings showed a significant difference in free radical concentration between gastritis and tumour samples and an overall trend towards increased radical levels in gastritis tissue. When radical levels in gastritis samples were analysed with regards to Helicobacter pylori infection, no clear link could be established. RSM was used for mutation detection analysis on the p53 gene and the elucidation of a mutational fingerprint for ROS. RSM was able to detect hydrogen peroxide mediated DNA damage in a gastric cell line. The majority of these mutations were GC (r) AT transitions, which were also the mutation types detected in biopsy samples. My results also showed that p53 was mutated in a large proportion of gastritis and intestinal metaplasia samples. These findings suggest that ROS induced mutations of p53 are involved in the initiation of gastric cancer. When the ROS induced p53 mutations in gastritis samples were matched to Helicobacter pylori status and strain virulence, only a tenuous relationship appeared to exist. Therefore, oxidative damage is an important risk factor in gastric cancer, with H. pylori contributing to genetic instability in a sub population of individuals. |
